U.S. patent number RE35,877 [Application Number 08/563,094] was granted by the patent office on 1998-08-25 for automatic light modulating camera.
This patent grant is currently assigned to Nikon Corporation. Invention is credited to Tadao Takagi.
United States Patent |
RE35,877 |
Takagi |
August 25, 1998 |
Automatic light modulating camera
Abstract
An automatic light modulating camera effecting a preliminary
light emission and a main light emission, extracts effective light
metering areas from plural light metering areas based on the light
metering signals obtained at the preliminary light emission and on
lens signals indicating the states of a phototaking lens at the
preliminary light emission, and terminates the main light emission
based on the light metering signals obtained in the effective light
metering areas.
Inventors: |
Takagi; Tadao (Yokohama,
JP) |
Assignee: |
Nikon Corporation (Tokyo,
JP)
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Family
ID: |
27465097 |
Appl.
No.: |
08/563,094 |
Filed: |
November 27, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
672055 |
Mar 13, 1991 |
05268730 |
Dec 7, 1993 |
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Foreign Application Priority Data
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Mar 19, 1990 [JP] |
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2-69251 |
Apr 3, 1990 [JP] |
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2-88898 |
Apr 3, 1990 [JP] |
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2-88899 |
Apr 3, 1990 [JP] |
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2-88900 |
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Current U.S.
Class: |
396/157;
396/273 |
Current CPC
Class: |
G03B
7/08 (20130101); G03B 7/09974 (20150115); G03B
7/09976 (20150115); G03B 7/09979 (20150115); G03B
7/17 (20150115) |
Current International
Class: |
G03B
7/16 (20060101); G03B 015/05 () |
Field of
Search: |
;396/157,273 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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60-15626 |
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Jan 1985 |
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JP |
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62-90633 |
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Apr 1987 |
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JP |
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62-169134 |
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Jul 1987 |
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JP |
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2067773 |
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Jul 1981 |
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GB |
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Other References
Patent Abstracts of Japan, vol. 10, No. 183 (P-472) Jun. 26, 1986.
.
Patent Abstracts of Japan, vol. 6, No. 41 (P-106)(919) Mar. 13,
1982. .
Patent Abstracts of Japan, vol. 14, No. 286 (P-1064) Jun. 20,
1990..
|
Primary Examiner: Adams; Russell E.
Attorney, Agent or Firm: Shapiro and Shapiro
Claims
I claim:
1. An automatic light modulating camera capable of a flash
phototaking operation with a preliminary light emission followed by
a main light emission, comprising:
light metering means for metering reflected light from each of
plural areas divided in an object field at said preliminary ad main
light emissions and outputting corresponding light metering
signals;
area extracting means for extracting effective light metering areas
from said plural areas, based on the light metering signals
obtained at said preliminary light emission and on lens signals
indicating the phototaking state of a phototaking lens at said
preliminary light emission; and
light modulating means for terminating said main light emission,
according to the light metering signals obtained in said effective
light metering areas.
2. An automatic light modulating camera according to claim 1,
wherein said leans signals include the aperture value and the
phototaking distance of the phototaking lens.
3. An automatic light modulating camera according to claim 1,
wherein said light modulating means includes a gain-adjustable
processing circuit for synthesizing the light metering signals
obtained at said main light emission, based on the light metering
signals obtained from said effective light metering as at said
preliminary light emission, and wherein said light modulating means
terminates said main light emission when the sum of said light
metering signals synthesized by said processing circuit reaches a
predetermined light modulating level.
4. An automatic light modulating camera according to claim 3,
wherein said processing circuit comprises amplifiers for amplifying
said light metering signals, and an integrating circuit for
synthesizing said light metering signals as amplified by said
amplifiers.
5. An automatic light modulating camera according to claim 1,
wherein said light modulating means is adapted to determine a
relationship, to be used for terminating the main light emission,
between the sum of said light metering signals and the light
modulating level, based on the light metering signals obtained from
said effective light metering areas at said preliminary light
emission, and to terminate said main light emission when said sum
and said light modulating level reach said relationship.
6. An automatic light modulating camera according to claim 1,
further comprising weighting means for weighting the light metering
signals of said effective light metering areas, wherein the weights
include weights corresponding to the exit pupil distance of the
phototaking lens.
7. An automatic light modulating camera according to claim 1,
wherein said light metering means has photosensors each producing a
light metering signal for a corresponding one of said plural areas,
said light modulating means has amplifiers each corresponding to
one of said photosensors and amplifying the light metering signal
therefrom, and gains of said amplifiers are changed on the basis of
the light metering signals of said effective light metering areas
obtained at said preliminary light emission.
8. An automatic light modulating camera according to claim 1,
wherein said light metering means has photosensors each producing a
light metering signal for a corresponding one of said plural areas,
said light modulating means has an adding circuit for combining
light metering signals from each of said photosensors and an
integrating circuit for integrating an output from said adding
circuit, and a gain of said integrating circuit is changed on the
basis of the light metering signals of said effective light
metering areas obtained at said preliminary light emission.
9. An automatic light modulating camera capable of a flash
phototaking operation with a flash light emission, comprising:
light metering means for metering reflected flash light from each
of plural means divided in an object field at said light emission
and outputting corresponding light metering signals;
area extracting means for extracting effective light metering areas
from said plural areas, based on the light metering signals
obtained in an initial stage of said light emission and on lens
signals indicating the phototaking state of a phototaking lens at
said light emission; and
light modulating means for terminating said light emission,
according to the light metering signals obtained in said effective
light metering areas extracted by said area extracting means.
10. An automatic light modulating camera according to claim 9,
wherein said lens is include the aperture value and the phototaking
distance of the phototaking lens.
11. An automatic light modulating camera according to claim 9,
wherein said light modulating means includes a gain-adjustable
processing circuit for synthesizing the light metering signals
obtained at said light emissions, based on the light metering
signals obtained from said effective light metering area in the
initial stage of said light emission, and wherein said light
modulating means terminates said light emission when the sum of
said light metering signals synthesized by said processing circuit
reaches a predetermined light modulating level.
12. An automatic light modulating camera according to claim 11,
wherein said processing circuit comprises amplifiers for amplifying
said light metering signals, and an integrating circuit for
synthesizing said light metering signals as amplified by said
amplifiers.
13. An automatic light modulating camera according to claim 9,
wherein said light modulating means is adapted to determine a light
modulating level for terminating said light emission, based on the
light metering signals obtained from said effective light metering
areas in an initial stage of said light emission, and to terminate
said light emission when the sum of said light metering signals at
said light emission reaches said light modulating level.
14. An automatic light modulating camera according to claim 9,
further comprising weighting means for weighting the light metering
signals of said effective light metering areas, wherein the weights
include weights corresponding to the exit pupil distance of the
phototaking lens.
15. An automatic light modulating camera according to claim 9,
wherein said light metering means has photosensors each producing a
light metering signals for a corresponding one of said plural
areas, said light modulating means has amplifiers each
corresponding to one of said photosensors and amplifying the light
metering signal therefrom, and gains of said amplifiers are changed
on the basis of the light metering signals of said effective light
metering areas obtained at said initial stage of said light
emission.
16. An automatic light modulating camera according to claim 9,
wherein said light metering means has photosensors each producing a
light metering signal for a corresponding one of said plural areas
said light modulating means has an adding circuit for combining
light metering signals from each of said photosensors and an
integrating circuit for integrating an output from said adding
circuits and a gain of said integrating circuit is changed on the
basis of the light metering signals of said effective light
metering areas obtained at said initial stage of said light
emission.
17. An automatic light modulating camera capable of a flash
phototaking operation with a preliminary light emission followed by
a main light emission, comprising:
light metering means for metering reflected light from each of
plural areas divided in an object field at said preliminary and
main light emissions and outputting corresponding light metering
signals:
area extracting means for extracting effective light metering areas
from said plural areas, based on the light metering signals
obtained at said preliminary light emission and on lens signals
indicating the phototaking state of a phototaking lens at said
preliminary light emission; and
light modulating means for determining a relationship, to be used
for terminating said main light emission, between a predetermined
light modulation evaluation factor to be cumulatively calculated
from the light metering signals of said effective light metering
areas and the light modulating level, based on the size of said
effective light metering areas extracted by said area extracting
means, and terminating said main light emission when said
predetermined light modulation evaluation factor and said light
modulating level reach said relationship.
18. An automatic light modulating camera according to claim 17
wherein said light modulating means is adapted to vary said light
modulating level according the size of said effective light
metering areas.
19. An automatic light modulating camera according to claim 17,
wherein said light modulating means comprises amplifiers and an
integrating circuit for processing the light metering signals of
said effective light metering areas and is adapted to vary one of
the gain of said amplifiers and the gain of said integrating
circuit according to the size of said effective light metering
areas thereby varying said predetermined light modulation
evaluation factor.
20. An automatic light modulating camera according to claim 17
wherein the size of said effective light metering areas depends on
the number thereof.
21. An automatic light modulating camera according to claim 17,
wherein said lens signals include the aperture value and the
phototaking distance of the phototaking lens.
22. An automatic light modulating camera according to claim 17,
further comprising weighting means for weighting the light metering
signals of said effective light metering areas, wherein the weights
include weights corresponding to the exit pupil distance of the
phototaking lens.
23. An automatic light modulating camera according to claim 17,
wherein said light metering means has photosensors each producing a
light metering signal for a corresponding one of said plural areas,
said light modulating means has amplifiers each corresponding to
one of said photosensors and amplifying the light metering signal
therefrom, and gains of said amplifiers are changed according to
the size of said effective light metering areas to vary said
predetermined light modulation evaluation factor.
24. An automatic light modulating camera according to claim 17,
wherein said light metering means has photosensors each producing a
light metering signal for a corresponding one of said plural areas
said light modulating means has an adding circuit for combining
light metering signals from each of said photosensors and an
integrating circuit for integrating an output from said adding
circuit, and a gain of said integrating circuit is changed
according to the size of said effective light metering areas to
vary said predetermined light modulation evaluation factor.
25. An automatic light modulating camera capable of a flash
phototaking operation with a flash light emission, comprising:
light metering means for metering reflected flash light from each
of plural areas divided in an object field at said light emission
and outputting corresponding light metering signals;
area extracting means for extracting effective light metering as
from said plural area, based on the light metering signals obtained
in an initial stage of said light emission and on lens signals
indicating the phototaking state of a phototaking lens at said
light emission; and
light modulating means for determining a relationship, to be used
for terminating said light emission, a predetermined light
modulation evaluation factor to be cumulatively calculated from the
light metering signals of said effective light metering areas and
the light modulating level, based on the size of said effective
light metering areas, and terminating said light emission when said
predetermined light modulation evaluation factor and said light
modulating level reach said relationship after said initial stage
of the light emission.
26. An automatic light modulating camera according to claim 25,
wherein said light modulating means is adapted to vary said light
modulating level according the size of said effective light
metering areas.
27. An automatic light modulating camera according to claim 25,
wherein said light modulating means comprises amplifiers and an
integrating circuit for processing the light metering signals of
said effective light metering areas, and is adapted to vary one of
the gain of said amplifiers and the gain of said integrating
circuit according to the size of said effective light metering
areas, thereby varying said predetermined light modulation
evaluation factor.
28. An automatic light modulating camera according to claim 25,
wherein the size of said effective light metering areas depends on
the number thereof.
29. An automatic light modulating camera according to claim 25,
wherein said lens signals include the aperture value and the
phototaking distance of the phototaking lens.
30. An automatic light modulating camera according to claim 25,
further comprising weighting means for weighting the light metering
signals of said effective light metering, areas, wherein the
weights include weights corresponding to the exit pupil distance of
the phototaking lens.
31. An automatic light modulating camera according to claim 25,
wherein said light metering means has photosensors each producing a
light metering signal for a corresponding one of said plural areas,
said light modulating means has amplifiers each corresponding to
one of said photosensors and amplifying the light metering signal
therefrom, and gains of said amplifiers are changed according to
the size of said effective light metering areas to change said
predetermined light modulation evaluation factor.
32. An automatic light modulating camera according to claim 25
wherein said light metering means has photosensors each producing a
light metering signal for a corresponding one of said plural areas,
said light modulating means has an adding circuit for combining
light metering signals from each of said photosensors and an
integrating circuit for integrating an output from said adding
circuit, and a gain of said integrating circuit is changed
according to the size of said effective light metering areas to
vary said predetermined light modulation evaluation factor.
33. An automatic light modulating camera capable of a flash
phototaking operation with a preliminary light emission followed by
a main light emission, comprising:
light metering means for metering reflected light from each of
plural areas divided in an object field at said preliminary and
main light emissions and outputting corresponding light metering
signals;
reflection factor distribution calculating means for calculating
the reflection factor distributions of said plural areas of the
object field based on the light metering signals obtained at said
preliminary light emission; and
light modulating means for determining a relationship, to be used
for terminating said main light emission, between a predetermined
light modulation evaluation factor to be cumulatively calculated
from the light metering signals of said plural areas and the light
modulation level, based on said reflection factor distributions
calculated by said reflection factor distribution calculating
means, and terminating said main light emission when said
predetermined light modulation evaluation factor and said light
modulation level each said relationship.
34. An automatic light modulating camera according to claim
.[.20.]. .Iadd.33.Iaddend., wherein said light modulating means is
adapted to vary said light modulating level according to said
reflection factor distributions.
35. An automatic light modulating camera according to claim 33,
wherein said light modulating means comprises amplifiers and an
integrating circuit for processing the light metering signals of
said plural areas, and is adapted to vary one of the gain of said
amplifiers and the gain of said integrating circuit according to
said reflection factor distributions, thereby varying said
predetermined light modulation evaluation factor.
36. An automatic light modulating camera according to claim 33,
further comprising weighting means for weighting the light metering
signals of said plural areas, wherein the weights include weights
corresponding to the exit pupil distance of a phototaking lens.
37. An automatic light modulating camera according to claim 33,
wherein said light metering means has photosensors each producing a
light metering signal for a corresponding one of said plural areas,
said light modulating means has amplifiers each corresponding to
one of said photosensors and amplifying the light metering signal
therefrom, and gains of said amplifiers are changed according to
said reflection factor distributions to vary said predetermined
light modulation evaluation factor.
38. An automatic light modulating camera according to claim 33,
wherein said light metering means has photosensors each producing a
light metering signal for a corresponding one of said plural areas,
said light modulating means has an adding circuit for combining
light metering signals from each of said photosensors and an
integrating circuit for integrating an output from said adding
circuit, and a gain of said integrating circuit is changed
according to said reflection factor distributions to vary said
predetermined light modulation evaluation factor.
39. An automatic light modulating camera capable of a flash
phototaking operation with a with light emission, comprising:
light metering means for metering reflected flash light from each
of plural areas divided in an object field at said light emission
and outputting corresponding light metering signals;
reflection factor distribution calculating means for calculating
the reflection factor distributions of said plural areas of the
object field, based on the light metering signals obtained in an
initial stage of the light emission; and
light modulating means for determining a relationship, to be used
for terminating said light emission, between a predetermined light
modulation evaluation factor to be cumulatively calculated from the
light metering signal of said plural areas and the light modulating
level, based on said reflection factor distributions calculated by
said reflection factor distribution calculating means, and
terminating said light emission when said predetermined light
modulation evaluation factor and said light modulating level reach
said relationship after said initial stage of light emission.
40. An automatic light modulating camera according to claim 39,
wherein said light modulating means is adapted to vary said light
modulating level according to said reflection factor
distributions.
41. An automatic light modulating camera according to claim 39,
wherein said light modulating means comprises amplifiers and an
integrating circuit for processing the light metering signals of
said plural areas, and is adapted to vary one of the gain of said
amplifiers and the gain of said integrating circuit according to
said reflection factor distributions thereby varying said
predetermined light modulation evaluation factor.
42. An automatic light modulating camera according to claim 39,
further comprising weighting means for weighting the light metering
signals of said plural areas, wherein the weights includes weights
corresponding to the exit pupil distance of a phototaking lens.
43. An automatic light modulating camera according to claim 39,
wherein said light metering means has photosensors each producing a
light metering signal for a corresponding one of said plural areas,
said light modulating means has amplifiers each corresponding to
one of said photosensors and amplifying the light metering signal
therefrom, and gains of said amplifiers are changed according to
said reflection factor distributions to vary said predetermined
light modulation evaluation factor.
44. An automatic light modulating camera according to claim 39,
where in said light metering means has photosensors each producing
a light metering signal for a corresponding one of said plural
areas, said light modulating means has an adding circuit for
combining light metering signals from each of said photosensors and
an integrating circuit for integrating an output from said adding
circuit, and a gain of said integrating circuit is changed
according to said reflection factor distributions to vary said
predetermined light modulation evaluation factor.
45. An automatic light modulating camera capable of a flash
phototaking operation with a preliminary light emission followed by
a main light emission, comprising:
light metering means for metering reflected light from each of
plural areas divided in an object field at said preliminary and
main light emissions and outputting corresponding light metering
signals;
area extracting means for extracting effective light metering areas
from said plural areas, based on the light metering signals
obtained at said preliminary light emission and on lens signals
indicating the phototaking state of a phototaking lens at said
preliminary light emission;
reflection factor distribution calculating means for calculating
the reflection factor distribution of said extracted effective
light metering areas; and
light modulating means for determining a relationship, to be used
for terminating said main light emission, between a predetermined
light modulation evaluation factor to be cumulatively calculated
from the light metering signals of said effective light metering
areas and the light modulating level, based on the size and said
reflection factor distributions of said effective light metering
areas extracted by said area extracting means and terminating said
main light emission when said predetermined light modulation
evaluation factor and said light modulating level reach said
relationship.
46. An automatic light modulating camera according to claim 45,
wherein aid light modulating means is adapted to vary said light
modulating level according to the size and said reflection factor
distributions of said effective light metering areas.
47. An automatic light modulating camera according to claim 45,
wherein said light modulating means comprises amplifiers and an
integrating circuit for processing the light metering signals of
said effective light metering areas, and is adapted to vary one of
the gain of said amplifiers and the gain of said integrating
circuit according to the size and said reflection factor
distributions of said effective light metering areas, thereby
varying said predetermine light modulation evaluation so
factor.
48. An automatic light modulating camera according to claim 45,
further comprising weighting means for weighting the light metering
signals of said effective light metering areas, wherein the weights
include weights corresponding to the exit pupil distance of a
phototaking lens.
49. An automatic lights modulating camera according to claim 45,
wherein said light metering means has photosensors each producing a
light metering signal for a corresponding one of said plural areas,
said light modulating means has amplifiers each corresponding to
one of said photosensors and amplifying the light metering signal
therefrom, and gains of said amplifiers are changed according to
the size of said effective light metering areas and said reflection
factor distributions to vary said predetermined light modulation
evaluation factor.
50. An automatic light modulating camera according to claim 45,
wherein said light metering means has photosensors each producing a
light metering signal for a corresponding one of said plural areas,
said light modulating means has an adding circuit for combining
light metering signals from each of said photosensors and an
integrating circuit for integrating an output from said adding
circuit, and a gain of said integrating circuit is changed
according to the size of said effective light metering areas and
said reflection factor distributions to vary said predetermined
light modulation evaluation factor.
51. An automatic light modulating camera capable of a flash
phototaking operation with a flash light emission, comprising:
light metering means for metering reflected light from each of
plural areas divided in an object field at said light emission, and
outputting corresponding light metering signals;
area extracting means for extracting effective light metering areas
from said plural areas, based on the light metering signals
obtained in an initial stage of said light emission and on lens
signals indicating the phototaking state of a phototaking lens at
said light emission;
reflection factor distribution calculating means for calculating
the reflection factor distributions of said extracted effective
light metering areas; and
light modulating means for determining a relationship, to be used
for terminating said light emission, between a predetermined light
modulation evaluation factor to be cumulatively calculated from the
light metering signals of said effective light metering areas and
the light modulating level, based on the size and said reflection
factor distributions of said effective light metering areas, and
terminating said light emission when said predetermined light
modulation evaluation factor and said light modulating level reach
said relationship, after said initial stage of light emission.
52. An automatic light modulating camera according to claim 51,
wherein said light modulating means is adapted to vary said light
modulating level according to the size and said reflection factor
distributions of said effective light metering areas.
53. An automatic light modulating camera according to claim 51,
wherein said light modulating means comprises amplifiers and an
integrating circuit for processing the light metering signals of
said effective light metering areas, and is adapted to vary one of
the gain of said amplifiers and the gain of said integrating
circuit according to the size and said reflection factor
distributions of said effective light metering areas thereby
varying said predetermined light modulation evaluation factor.
54. An automatic light modulating camera according to claim 51,
further comprising weighting means for weighting the light metering
signals of said effective light metering areas, wherein the weights
include weights corresponding to the exit pupil distance of a
phototaking lens.
55. An automatic light modulating camera according to claim 51,
wherein said light metering means has photosensors each producing a
light metering signal for a corresponding one of said plural areas,
said light modulating means has amplifiers each corresponding to
one of said photosensors and amplifying the light metering signal
therefrom, and gains of said amplifiers are changed according to
the size of said effective light metering areas and said reflection
factor distributions to vary said predetermined light modulation
evaluation factor.
56. An automatic light modulating camera according to claim 31,
wherein said light metering means has photosensors each producing a
light metering signal for a corresponding one of said plural areas,
said light modulating means has an adding circuit for combining
light metering signals from each of said photosensors and an
integrating circuit for integrating an output from said adding
circuit, and a gain of said integrating circuit is changed
according to the size of said effective light metering areas and
said reflection factor distributions to vary said predetermined
light modulation evaluation factor.
57. An automatic light modulating camera capable of a flash
phototaking operation with a preliminary light emission followed by
a main light emission, comprising:
light metering means for metering reflected light from each of
plural areas divided in an object field at said preliminary and
main light emissions and outputting corresponding light metering
signals;
level determination means for determining a light modulating level,
based on the light metering signals obtained at said preliminary
light emission;
level correction means for correcting said determining light
modulating level into a predetermined range if said level is
outside said range; and
light modulating means for terminating said main light emission
when a predetermined light modulation evaluation factor, to be
cumulatively calculated from said light metering signals at said
main light emission, reaches said determined light modulating level
if that level is in said range, or reaches said corrected light
modulating level if said determined light modulating level is
outside said range.
58. An automatic light modulating camera according to claim 57,
further comprising weighting means for weighting the light metering
signals of said plural areas, wherein the weights include weights
corresponding to the exit pupil distance of a phototaking lens.
59. An automatic light modulating camera capable of a flash
phototaking operation with a flash light emission, comprising:
light metering means for metering reflected flash light from each
of plural areas divided in an object field at said light emission,
and outputting corresponding light metering signals;
level determination means for determining a light modulating level,
based on the light metering signals obtained in an initial stage of
said light emission;
level correction means for correcting said determined light
modulating level into a predetermined range if said level is
outside said range; and
light modulating means for terminating said light emission when a
predetermined light modulation evaluation factor, to be
cumulatively calculated from said light modulating signals, reaches
said determined light modulating level if that level is in said
range, or reaches said corrected light modulating level if said
determined light modulating level is outside said range.
60. An automatic light modulating camera according to claim 59, the
comprising weighting means for weighting the light metering signals
of said plural areas wherein the weights include weights
corresponding to the exit pupil distance of a phototaking lens.
61. A phototaking lens barrel mountable to an automatic light
modulating camera capable of a flash phototaking operation with a
preliminary light emission followed by a main light emission,
comprising:
detection means for determining lens signals indicating a
phototaking state; and
output means for sending said lens signals to said automatic light
modulating camera;
wherein said camera is adapted to extract effective light metering
areas to be used at said main light emission from plural areas
divided in an object field, based on light metering signals
obtained by metering reflected light from said plural areas at said
preliminary light emission and on said lens signals at said
preliminary light emission.
62. A phototaking lens barrel according to claim 61, wherein said
lens signals indicate phototaking distance and aperture value.
.Iadd.
63. An automatic light modulating camera capable of a flash
phototaking operation with a preliminary light emission followed by
a main light emission, comprising:
a light metering circuit which has a plurality of photosensor
elements corresponding to plural areas divided in an object field,
said light metering circuit metering reflected light from said
plural areas at said preliminary and main light emissions and
outputting corresponding light metering signals;
an area extracting circuit connected with said light metering
circuit which extracts effective light metering areas from said
plural areas, based on the light metering signals obtained at said
preliminary light emission and on lens signals indicating the
phototaking state of a phototaking lens; and
a light modulating circuit which terminates said main light
emission, according to the light metering signals obtained in said
effective light metering areas. .Iaddend..Iadd.64. An automatic
light modulating camera capable of a flash phototaking operation
with a flash light emission, comprising:
a light metering circuit which has a plurality of photosensor
elements corresponding to plural areas divided in an object field,
said light metering circuit metering reflected light from said
plural areas at said light emission and outputting corresponding
light metering signals;
an area extracting circuit connected with said light metering
circuit which extracts effective light metering areas from said
plural areas, based on the light metering signals obtained at an
initial stage of said light emission and on lens signals indicating
the phototaking state of a phototaking lens; and
a light modulating circuit which determines a relationship, to be
used for terminating said light emission, between a predetermined
light modulation evaluation factor to be cumulatively calculated
from the light metering signals of said effective light metering
areas and a light modulating level, based on the size of said
effective light metering areas, and which terminates said light
emission when said predetermined light modulation evaluation factor
and said light modulating level reach said relationship
after said initial stage of said light emission. .Iaddend..Iadd.65.
A camera system including a camera and a flashing device,
comprising:
a release switch provided on a body of the camera and operable
externally of the camera body;
a release circuit provided in the camera body for generating a
release signal in response to an operation of said release
switch;
a photometry circuit, including a divisional photometry device,
which performs photometry of an object field with the object field
being divided into a plurality of areas;
a flashing signal generating circuit which generates, in response
to said release signal, a signal for causing said flashing device
to effect preliminary flashing and a signal for causing said
flashing device to effect a subsequent main flashing;
a flashing circuit responsive to the signals from said flashing
signal generating circuit for effecting said preliminary flashing
and said main flashing; and
a flashing control circuit for controlling a quantity of emitted
light of said flashing device;
wherein during said preliminary flashing, said photometry circuit
measures light of the preliminary flashing reflected from the
object field, and during said main flashing, said photometry
circuit measures light of the main flashing reflected from the
object field; and
wherein said flashing control circuit controls the quantity of
emitted light of said main flashing based on a photometry result of
said
photometry circuit for said preliminary flashing.
.Iaddend..Iadd.66. A camera system including a camera and a
flashing device, comprising:
a release switch provided on the body of the camera and operable
externally of the camera body;
a release circuit provided in the camera body for generating a
release signal in response to an operation of said release
switch;
a photometry circuit, including a divisional photometry device,
which performs photometry of an object field with the object field
being divided into a plurality of areas;
a flashing signal generating circuit which generates, in response
to said release signal, a signal for causing said flashing device
to effect preliminary flashing and a signal for causing said
flashing device to effect a subsequent main flashing;
a flashing circuit responsive to the signals from said flashing
signal generating circuit for effecting said preliminary flashing
and said main flashing;
a flashing control circuit for controlling a quantity of emitted
light of said flashing device; and
a light shielding member movable between a position at which said
shielding member shields a film surface and a position at which
said shielding member does not shield the film surface;
wherein during said preliminary flashing, said photometry circuit
measures light of the object field reflected by said light
shielding member, and during said main flashing, said photometry
circuit measures light of the object field reflected by the film
surface; and
wherein said flashing control circuit controls the quantity of
emitted light of said main flashing based on a photometry result of
said
photometry circuit for said preliminary flashing.
.Iaddend..Iadd.67. A camera system according to claim 66, wherein
said light shielding member includes a shutter blade.
.Iaddend..Iadd.68. In a camera system including a camera and a
flashing device, a method of performing flash photography,
comprising:
causing the flashing device to effect a preliminary flashing upon
input of a signal for starting flash photography;
performing photometry of light of said preliminary flashing coming
from an object field and reflected by a light shielding member
shielding a film surface;
calculating a quantity of light required for a main flashing based
on a result of said photometry;
effecting said main flashing with said flashing device after
shifting said light shielding member to a position at which said
light shielding member does not shield the film surface;
performing photometry of light of said main flashing coming from
the object field and reflected by the film surface;
stopping the main flashing when a photometry result of the light of
the object field reflected by the film surface corresponds to said
calculated quantity of light; and
returning said light shielding member to the position in which said
light shielding member shields the film surface. .Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a TTL automatic light modulating
device for dividing the object field into plural light metering
areas and effecting light modulation based on a light metering
signal obtained from each of said area.
2. Related Background Art
The Japanese Laid-open Patent Sho 60-15626 discloses an automatic
light modulating camera.
This camera is provided, on the front face thereof, with a flash
emission unit for main light emission, an infrared flash unit for
preliminary light emission, and a light metering unit for receiving
thus emitted lights. Said light metering unit is so constructed as
to measure the light reflected from the object, in divided manner
in the central area and the peripheral area of the object
field.
In this camera, at first the infrared flash emission unit emits
infrared light, and the light reflected from the object is measured
in the central and peripheral areas of the object field. Based on
the difference in the reflected lights, there is identified whether
the main object is in the central or peripheral area. According to
the result of said identification, the light metering method of
said light metering unit is switched to the center priority
metering, periphery priority metering or average metering.
Then the flash emission unit emits light in synchronization with
the shutter releasing operation. In the course of said light
emission, the reflected light from the object is measured in
divided manner according to said switched light metering method,
and the flash emission unit terminates light emission when the
integrated reflected light reaches a predetermined value.
Also the Japanese Laid-open Patent Sho 62-90633 discloses an
automatic light modulating camera which does not effect preliminary
light emission, but which effects light metering in divided areas
of the object field at the main flash emission and controls the
amount of main flash emission by the detected maximum value.
In such conventional automatic light modulating cameras, if an
article of high reflectance such as a metal screen or a mirror is
present behind the main object or if in article is present in front
of the main object, the position of the main object cannot be
correctly recognized because of the excessively high light metering
signal from the area in which such article is located, and the
exposure for the main object may become incorrect by the influence
of such article.
Also in such conventional automatic light modulating cameras, the
main object may be over or under exposed because the light
modulating level for terminating the main flash emission is defined
to be constant.
SUMMARY OF THE INVENTION
The object of the present invention is to always give an
appropriate exposure to the main object at the flash photographing,
even in the presence of a highly reflective article in the object
field or of an article in front of the main object.
The above-mentioned object can be attained, according to the
present invention, by a camera effecting a preliminary light
emission and a main light emission, which extracts effective light
metering areas from divided plural light metering areas based on
the light metering signals obtained at the preliminary light
emission and on lens signals indicating the states (for example,
diaphragm aperture and object distance) of the phototaking lens at
the preliminary light emission, and terminates the main light
emission based on the light metering signal obtained in said
effective light metering areas.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 to 4 are diagrams showing pertinent portions of cameras
according to the present invention.
FIGS. 5 to 15 illustrate a first embodiment of the present
invention, wherein:
FIG. 5 is a schematic cross-sectional view of an automatic light
modulating camera of the present invention;
FIG. 6 is a perspective view of a condensing lens array and a
divided photosensor element;
FIG. 7 is a view showing positional relationship between the
divided photosensor element and film exposure areas;
FIG. 8 is a block diagram of a control system;
FIG. 9 is a block diagram of a light modulating circuit;
FIG. 10 is a flow charts of the main control sequence;
FIGS. 11 to 15 are flow charts of the subroutines;
FIG. 16 is a flow chart of the control sequence of a second
embodiment which is a variation of the flow chart shown in FIG. 14;
and
FIG. 17 is a flow chart of the control sequence of a third
embodiment which is a variation of the flow chart shown in FIG.
14.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIGS. 1 to 4 are diagrams showing pertinent portions of cameras
according to the present invention.
Referring to FIG. 1, a TTL automatic light modulating camera is
provided with flash means 101 capable of a main light emission for
flash photographing of the object field and a primary light
emission for detecting the reflective factor distributions of the
object field prior to the main light emission; light metering means
102 for dividing the object field into plural arms metering the
reflected light from each of said plural areas at the main and
preliminary light emissions by said flash means 101, and outputting
corresponding light metering signals; area extracting means 103 for
extracting effective light metering areas from said divided plural
area, based on the light metering signals obtained at the
preliminary light emission and on the diaphragm aperture and object
distance of the phototaking lens at said preliminary light emission
and light modulating means 104 for terminating said main light
emission according to the light metering signals obtained in said
effective light metering areas extracted by the area extracting
means 103.
Also embraced by FIG. 1 is a TTL automatic light modulating camera
is provided with flash means 101 for emitting light for flash
photographing of the object field; light metering means 102 for
dividing the object field into plural areas, metering the reflected
light from each of said plural areas at the light emission by the
flash means 101, and outputting corresponding light metering
signals; area extracting means 103 for extracting effective light
metering areas from said divided plural areas, based on the light
metering signals obtained in an initial stage of the light emission
and on the diaphragm aperture and object distance of the
phototaking lens at the light emission; and light modulating means
104 for terminating the light emission according to the light
metering signals obtained in the effective light metering areas
extracted by said area extracting means 103.
Referring to FIG. 2 a TTL automatic light modulating camera is
provided with flash means 101 capable of a main light emission for
flash photographing of the object field and a preliminary light
emission prior to said main light emission; light metering means
102 for dividing the object field into plural areas metering the
reflected light from each of said divided plural areas at the
preliminary and main light emissions by the flash means 101 and
outputting corresponding light metering signals; area extracting
means 203 for extracting effective light metering areas from said
divided plural areas, based on the light metering signals obtained
at the preliminary light emission; determination means 204 for
determining a light modulating level according to the size of the
extracted effective light metering areas; and light modulating
means 205 for terminating the main light emission when a
predetermined light modulation evaluation factor, cumulatively
calculated according to the light metering signals from the
effective light metering areas reaches the determined light
modulating level in the course of the main light emission.
Also embraced by FIG. 2 is a TTL automatic light modulating camera
provided with flash means 101 for flash photographing of the object
field; light metering means 102 for dividing the object field into
plural areas, metering the reflected light from each of said plural
areas the light emission by said flash means 101 and releasing
corresponding light metering signals; area extracting means 203 for
extracting effective light metering areas from said divided plural
areas, based on the light metering said obtained in an initial
stage of the light emission; determination means 204 for
determining a light modulating level according to the size of the
extracted effective light metering areas; and light modulating
means 205 for terminating the light emission when a predetermined
light modulation evaluation factor, cumulatively calculated
according to the light metering signals from the effective light
metering areas, reaches the determined light modulating level.
Referring to FIG. 3A, a TTL automatic light modulating camera is
provided with flash means 101 capable of a main light emission for
flash photographing of the object field and a preliminary light
emission for detecting the reflection factor distribution of the
object field prior to the main light emission; light metering means
102 for dividing the object field into plural areas, metering the
reflected light from each of said plural areas at the preliminary
and main light emissions by the flash means 101, and outputting
corresponding light metering signals; reflection factor
distribution calculating means 103 for calculating the reflection
factor distributions in the plural areas of the object field, based
on the light metering signals obtained at the preliminary light
emission; determination means 204 for determining a light
modulating level based on the calculated reflection factor
distributions; and light modulating means 305 for terminating the
main light emission when a predetermined light modulation
evaluation factor, cumulatively calculated according to the light
metering signals, reaches said determined light modulating level in
the course of the main light emission.
Referring to FIG. 3B, a TTL automatic light modulating camera is
provided with flash means 101 for emitting light for flash
photographing of the object field; light metering means for
dividing the object field into plural areas, metering the reflected
light from each of the plural areas at the light emission by said
flash means 101 and outputting corresponding light metering
signals; reflection factor distribution calculating means 306 for
calculating the reflection factor distributions in the plural areas
of the object field, based on the light metering signals obtained
in an initial stage of the light emission; determination means 307
for determining a light modulating level, based on the calculated
reflection factor distributions; and light modulating means 308 for
terminating the light emission when a predetermined light
modulation evaluation factor, cumulatively calculated according to
the light metering signals, reaches the determined light modulating
level after the initial stage of the light emission.
Referring to FIG. 4, a TTL automatic light modulating camera is
provided with flash means 101 capable of a main light emission for
flash photographing of the object field and a preliminary light
emission prior to the main light emission; light metering means 102
for dividing the object field into plural areas, metering the
reflected light from each of said plural areas at the preliminary
and main light emissions by the flash means 101 and outputting
corresponding light metering signals; level determination means 403
for determining a light modulating level based on the light
metering signals at the preliminary light emission; level
correcting means 404 for correcting the determined light modulating
level into a predetermined range if said level is outside said
range; and light modulating means 405 for terminating the main
light emission when a predetermined light modulation evaluation
factor, cumulatively calculated according to the light metering
signals, reaches said determined or corrected light modulating
level in the course of the main light emission.
Also embraced by FIG. 4 is a TTL automatic light modulating camera
is provided with flash means 101 for emitting light for flash
photographing of the object field; light metering means 102 for
dividing the object field into plural areas, metering the reflected
light from each of said plural areas at the light emission by the
flash means 101 and releasing corresponding light metering signals;
level determination means 403 for determining a light modulating
level according to the light metering signals obtained at an
initial stage of the light emission; level correcting means 404 for
correcting the light modulating level into a predetermined range if
said level is outside said range; and light modulating means 405
for terminating the light emission when a predetermined light
modulation evaluation factor, cumulatively calculated according to
the light metering signals, reaches said determined or corrected
light modulating level after the initial stage of the light
emission.
The term reflection factor distribution means the distribution of
reflectance when reflective objects in the object field are assumed
to be at a same object distance, and is obtained, in the
embodiments of the present invention, by detecting the distribution
of light reflected from the object field through divided metering
of the reflected light therefrom.
In the following there will be explained a first embodiment of the
present invention, with reference to FIGS. 5 to 15.
FIG. 5 is a cross-sectional view of a TTL automatic light
modulating camera. A light beam transmitted by a phototaking lens 2
is reflected by a mirror 3 in a broken-lined lowered state, then
transmitted by a focusing screen 4 and a pentagonal prism 5, party
guided to an eyepiece lens 6 and partly guided to a light-metering
element 8 for exposure calculation through a condenser lens 7. When
a shutter release button (not shown) is depressed, the mirror 3 is
shifted to a solid-lined lifted position. Then, a diaphragm 9 is
closed to a predetermined aperture and a shutter 10 is opened and
closed, whereby a film FI is exposed to the light coming from the
object through the phototaking lens 2.
In the flash photographing operation, an electronic flash device 11
effects a main light emission to illuminate the object after the
shutter 10 is opened. The light reflected from the object reaches
the film through the phototaking lens 2, then is reflected by said
film and reaches a light modulating photosensor element 13 through
a condensing lens array 12. The camera of the present embodiment is
also capable of a preliminary light emission, prior to said main
light emission, for detecting the reflection factor distribution in
the object field. The light reflected from the object field, at
said preliminary light emission, is reflected by the shutter blinds
before the opening of the shutter and received by the photosensor
element 13.
As shown in FIG. 6, said photosensor element 13 is divided into a
photosensor element 13a corresponding to a circular light metering
area at the center of the object field, and photosensor elements
13b-13e corresponding to light metering areas of a rectangular form
eclipsed by an arc, at the peripheral portion of the object field,
all elements being positioned on the same plane. Thus, in the
present embodiment, the light metering is conducted in five
division areas of the object field by the preliminary light
emission prior to the main light emission. The condensing lens
array 12 is an optical member having three lens portions 12a-12c
respectively corresponding to the left, central and right blocks of
said photosensor elements 13a-13e.
FIG. 7 illustrates the optical positional relationship among an
exposure area 20 on the film, the photosensor element 13 and the
condensing lens array 12. When the exposure area 20 of a frame on
the film is divided into five areas, consisting of a circular
central area 20a and four peripheral areas 20b-20e, in the same
manner as in the object field, the left, central and right blocks
of the photosensor elements 13a-13e shown in FIG. 6 respectively
correspond, as indicated by broken lines in FIG. 7, to the left,
central and right areas of said exposure area 20 through three lens
portions 12a-12c of the condensing lens array 12. The five
photosensor elements 13a-13e respectively correspond, in shape, to
the areas 20a-20e of the exposure area 20 and can therefore measure
the luminances in said areas.
FIG. 8 is a block diagram of a control system. A CPU 31 for
controlling the sequence of the entire camera is connected to a
release circuit 32 for the shutter release button, a control
circuit for the shutter 10, a control circuit for the diaphragm 9
and a lens information output circuit 33 provided in the
phototaking lens 2. Said CPU 31 is further connected to a light
metering circuit 34 for effecting the light metering according to
the output from the exposure controlling photosensor element 8, a
light modulating circuit 40 for effecting light modulation
according to the outputs from the photosensor elements 13a-13e, an
ISO sensitivity detecting circuit 35 for reading the ISO
sensitivity of the loaded film FI from a DX code, and a light
emission control circuit 36 for said electronic flash device 11.
Said electronic flash device 11 is either incorporated in the
camera body or detachably mounted thereon.
The exposure controlling photosensor element 8 is composed, like
the photosensor element 13, of five photosensor elements 8a-8e
corresponding to the light metering areas in the object field. The
lens information output circuit 33 is composed of a lens ROM
storing information specific to the lens (fully-open aperture
value, exit pupil distance etc.), and a lens encoder for detecting
the object distance from the focus position of the phototaking lens
2.
FIG. 9 shows the details of said light modulating circuit 40,
including amplifiers 41a-41e for amplifying the outputs of the
photosensor elements 13a-13e; and gain setters 42a-42e for setting
the gains of said amplifiers 41a-41e in response to instructions
from the CPU 31 and respectively including D/A converter for
converting digital signals from said CPU 31 into analog
signals.
There are further provided integrating circuits 43a-43e for
integrating in time the outputs of said amplifiers 41a-41e at said
preliminary light emission, in response to an instruction from said
CPU 31; an adding circuit 44 for adding the outputs of the
amplifiers 41a-41e at the main light emission; an integrating
circuit 45 for integrating in time the result of addition obtained
by said adding circuit 44, in response to an instruction from the
CPU 31; a converting circuit 46 for converting a light modulating
level (to be explained later in more detail) released in the form
of a digital signal by the CPU 31 into an analog signal; and a
comparator 47 for comparing thus converted light modulating level
with the output of said integrating circuit 45 and releasing a
light emission stop signal when said output of the integrating
circuit 45 reaches said light modulating level.
In the following there will be explained the control sequence of
the CPU 31 in a flash photographing operation, with reference to
the flow charts shows in FIGS. 10 to 15.
FIG. 10 shows a main flow chart. When the shutter release button is
fully depressed in a step S1, in succession to a half-stroke
depression, a sequence starting from a step S2 is activated. At
first a step S2 reads the ISO sensitivity SV of the loaded film,
from the ISO sensitivity detecting circuit 35. The steps S3-S5 read
the fully-open aperture value F.sub.0, exit pupil distance P.sub.0
and object distance x from the lens information output circuit 33
of the phototaking lens 2, and the sequence proceeds to a step S6.
The object distance x is obtained by detecting, with the encoder,
the position of the phototaking lens driven in response to the
half-stroke depression of the shutter release button 32.
The step S6 executes light metering under the stationary light.
More specifically the outputs of the aforementioned divided
photosensor elements 8a-8e (FIG. 8) are fetched by the light
metering circuit 34, which thus reads the logarithmically
compressed brightness values EVn (n=1-5) corresponding to the light
metering areas. In the present embodiment, the values n (1-5)
respectively correspond to the photosensor elements 8a-8e or
13a-13e. Then a step S7 calculates an exposure BV for stationary
light, based on the brightness values EVn and the ISO sensitivity
SV, for example according to a method disclosed in commonly
assigned U.S. Pat. No. 4,965,620.
Then a step S8 determines the shutter speed TV and the aperture
value AV from thus calculated stationary light exposure BV, and a
step S9 lifts the mirror 3 from the broken-lined state shown in
FIG. 5 to the solid-lined state. Then a step S10 closes the
diaphragm 9 to an aperture determined in the step S8, and a step
S11 sends a light emission signal to the light emission control
circuit 36 to cause the electronic flash device 11 to effect the
preliminary light emission with a predetermined small guide number
G.sub.NO.
The light of said prelimination light emission is reflected by the
object, then transmitted by the phototaking lens 2, and is focused
as a primary image on the blinds of the shutter 10. Said primary
image is divided in five portions, which are respectively received
by the divided photosensor elements 13a-13e through the condensing
lens array 12 shown in FIG. 6 Said photosensor elements 13a--13e
send in succession signals, corresponding to the amounts of
received light, to the amplifiers 41a-41e of the light modulating
circuit 40 shown in FIG. 9.
The amplifiers 41a-41e amplify the input signals with gains set by
the gain setters 42a-42e (said gains being all "1" at the
preliminary light emission), for supply to the integrating circuits
43a-43e. In a step S12, the CPU 31 sends an activation signal to
the integrating circuits 43, which in response respectively
integrate said amplified signals in time and supply the CPU 31 with
the integrated signals, which will be hereinafter called divided
light metering signals BPn (n=1-5).
Thereafter the CPU 31 executes steps S13-S17 in succession, of
which details are shown in FIGS. 11 to 15.
FIG. 11 shows the details of a correction subroutine for lens and
element size (step S13 in FIG. 10) for said divided light metering
signals BPn. At first a step S131 sets a condition n=0. Then a step
S132 stepwise increases the value n by "1", and a step S133
calculates lens correction coefficients L(n) according to the
following equations:
wherein PO is the exit pupil distance of the phototaking lens 2.
Then a step S134 reads the element area correction coefficients
S(n) stored in advance in the memory, namely S(1)=1, S(2)=0.8,
S(3)=0.8, S(4)=1.3 and S(5)=1.3. Then a step S135 corrects the
divided light metering signals BPn according to a principle:
This operation is repeated until n=5 is identified in a step S136,
whereby the corrections for the lens and the element size are
conducted for all the divided light metering signals BPn of five
light metering areas.
The light-receiving conditions of said photosensor elements 13a-13e
vary, depending on the exit pupil distance PO of the phototaking
lens 2 and the size and position of said photosensor elements. The
above-explained corrections in the subroutine shown in FIG. 11 are
conducted in order to evaluate the light metering signals of all
the photosensor elements under the same condition.
Then, in a step S14 (FIG. 10), the CPU 31 executes an effective
light metering area determination (high/low cut subroutine), of
which details are shown in FIG. 12. At first, steps S1401, S1402
set conditions M=0, n=0 and steps S140-S1410 then execute following
processes in succession said five divided light metering signals
BPn, corrected in the step S13.
A step S1404 discriminate whether the divided light metering signal
satisfies a condition: ##EQU1## wherein G.sub.NO is the guide
number at the preliminary light emission, AV is the aperture value
(apex value) calculated in the foregoing step 8, x is the
photographing distance, and K1 is a constant. If the discrimination
of the step S1404 turns out affirmative, a step S1405 sets said
divided light metering signal to zero, then a step S1407 sets the
weight Dn for said light metering signal BPn also to zero, and the
sequence proceeds to a step S1411.
The meaning of said steps S1404-S1406 is as follows.
If an article of high reflectance, such as a metal screen or a
mirror, is present in the object field, or if an article is present
in front of the main object, the divided light metering signal BPn
of the area of such article is extremely large in comparison with
that of other objects, so that the main object may be under exposed
if the light modulation is conducted based on said light metering
signal. Therefore, the above-explained steps S1404-S1406 are to
exclude the light metering signal corresponding to such article of
high reflectance from the ensuing light modulating operation. More
specifically, if the light metering signal BPn is larger than a
reference value: ##EQU2## the light amount is identified as
excessively large, and said light metering signal BPn and the
corresponding weight Dn are both set at zero. This operation brings
about following effect since said reference value is determined
from the aperture value AV and photographing distance x at the
preliminary light emission.
Even if the preliminary light emission is conducted with a constant
guide number, the light metering signal varies depending on the
aperture value AV and photographing distance x, and becomes smaller
as the distance is longer or as the aperture is smaller. On the
other hand, if a constant reference value is adopted, an article to
be excluded may be overlooked under a condition of a long distance
or a small aperture, and a significant light metering signal may be
excluded at a short distance or a large aperture.
These drawbacks can be completely avoided in the present
embodiment, because said reference value is defined by the
above-explained equation and becomes larger as the phototaking
distance becomes shorter or as the aperture value is closer to the
fully-open aperture.
If the discrimination of the step S1404 turns out negative, the
sequence proceeds to a step S1407 to discriminate whether the light
metering signal BPn is smaller than a reference value K2. Deeding
whether it is smaller or not, the sequence respectively proceeds to
the above-mentioned spy S1405 or a step S1408. This procedure
serves in case the light metering signal BPn is excessively low
(for example, by a low reflection from a large space behind the
main object), to eliminate such signal BPn and thereby prevent the
over exposure of the main object. In this case, as the original
light metering signal BPn is weak, the reference value need not be
vaired according to the aperture value AV or the photographing
distance x but can be constant.
The light metering signals BPn not elm ted in the step S1404 or
S1407 are adopted in the original values in a step S1408, and a
step S1409 selects the weighting coefficients of "1" for said
signals. Then a step S1410 stepwise increases the variable M by
"1". Among five light metering areas in the object field, those of
which light metering signals BPn have not been eliminated
constitute effective light metering areas. The variable M indicates
the number of the uneliminated light metering signals BPn, or the
number of the effective light metering areas.
After the subroutine shown in FIG. 12 the sequence proceeds to a
step S15 (FIG. 10) for determining the reflection factor
distribution Rn of the light metering areas in the object
field.
FIG. 13 shows the details of said step S15. At first, steps S151,
S152 set conditions Q=0 and n=0. Then steps S153--S155 determine
the sum Q of the light metering signals BPn (Q=Q+BPn). As the
excessively strong or weak light metering signals have been set to
zero in the step S14, said sum practically includes only the light
metering signals of the effective light metering areas. Then a step
156 sets n=0, and steps S157-S159 determine the reflection factor
distribution Rn of each light metering signal BPn when the sum of
reflection factor of said signals BPn is normalized to "1",
according to an equation:
In this operation, the reflection factor distribution of a light
metering signal excluded in the step S14 becomes naturally to
zero.
Then the sequence proceeds to a step S16 (FIG. 10) for calculating
the light modulating level, which means the level of the light
metering signal for terminating the main light emission of the
electronic flash device 11 at the flash phototaking operation.
Now referring to FIG. 14 showing the details of said step S16, at
first a step S1601 sets the light modulating level LV to zero, and
a step S1602 sets a condition n=0. Then, subsequent steps
S1603-S1606 determine the light modulating level LV according the
number M of the effective light metering areas and the reflection
factor distribution thereof.
More specifically, a step S1604 discriminates whether the
reflection factor distribution Rn of each light metering signal is
equal to or larger than 1/M (corresponding to the average of the
reflection factor distribution Rn of the effective light metering
areas). If the result is affirmative, namely if said reflection
factor distribution is at least equal to the average the sequence
proceeds to a step S1605 to advance the light modulating level LV
by 0.02. On the other hand, if the discrimination in the step S1604
turns out negative, namely if the reflection factor distribution Rn
of the light metering area is less than the average value, the
sequence proceeds to a step S1606 to advance the light modulating
level by 0.02.times.Rn/MAX(R), wherein MAX(R) is the maximum value
of R1-R5.
The above-explained procedure is to bring the light modulating
level LV to 0.02.times.5=0.1 when five reflection factor
distributions are all equal, and determines the light modulating
level LV according the number of the effective light metering areas
M and the reflection factor distributions Rn. More specifically,
the light modulating level becomes smaller as the number of the
reflection factor distributions smaller than the average increases,
namely when the reflection factor distribution Rn is higher in
certain areas than in others and the difference in said
distribution becomes larger. Also said light modulating level
becomes smaller when the number M of the effective light metering
areas becomes smaller.
Since each light metering signal BPn is corrected in the step S13
according to the area of the photosensor elements 13a-13e, the
number M of the effective light metering areas depends on the area
of the entire effective light metering areas. Therefore the
determination of the light modulating level LV according to the
size of the effective light metering areas corresponds to the
determination of said level according to the number of said
effective light metering areas.
Then a step S1608 discriminates whether the determined light
modulating level LV is at least equal to a predetermined value
(0.03 in this case), and, if so, the sequence proceeds to a step
S610. If not, a step S1609 sets the light modulating level LV at
0.03, and the sequence then proceeds to said step S1610. This
sequence sets a lower limit of 0.03 to the light modulating level
LV, in order to prevent an under exposure resulting from an
excessively low light modulating level LV.
The step S1610 converts the light modulating level LV to a value
corresponding to the ISO sensitivity SV, read in the step S2,
according to an equation:
Then the sequence proceeds to a step S17 (FIG. 10) for determining
the weights for correcting the light metering signals at the
subsequent main light emission. Referring to FIG. 15 showing the
details of said step S17, at first a step S171 sets a condition
n=0, and steps S172-S174 determine new weights by multiplying the
weights Dn corresponding to the light metering signals (Dn being 1
or 0 as determined in the step S14) by L(n)/S(n), wherein L(n) is
the lens correction coefficient obtained in the step S13 and S(n)
is the area correction coefficient. In the present embodiment,
since the light modulating level LV is rendered variable according
to the aforementioned reflection factor distributions Rn, the
weights need not be varied according to the reflection factor
distributions but are determined solely from the lens correction
coefficients L(n) and the area correction coefficients S(n). The
weights corresponding to the light metering signals excluded in the
step S14 are naturally zero.
Then a step S18 (FIG. 10) opens the shutter 10, and, when it is
fully opened, causes the electronic flash device 11 to effect the
main light emission through the light emission control circuit 36,
and a step S19 meters the reflected light from the film surface in
divided manner. The illuminating light of the main light emission
is reflected by the object, then transmitted by the phototaking
lens 2, reflected by the film surface and received by the five
photosensor elements 13a-13e, of which output signals are
respectively modulating circuit 40 (FIG. 9). Then, in a step S20,
the CPU 31 sets the gains of the amplifiers 41a-41e by the gain
setters 42a-42e of the light modulating circuit 40 according to the
weights Dn determined in the step S17, thereby effecting the
weighting.
The amplifiers 41a-41e amplify the output signals of the
photosensor elements 13a-13e with thus set gains, and the amplified
signals are added in the adding circuit 44. A step S21 sends an
integrating signal to the integrating circuit 45, which in response
integrates in time the sum obtained from the adding circuit 44.
The light modulating level LV calculated in the step S16 is
converted into an analog signal in the converting circuit 46. The
output of said converting circuit 46 and the output of said
integrating circuit 45 (corresponding to the predetermined light
modulation evaluation fact to) are supplied to the comparator 47,
which sends a light emission stop signal to the CPU 31 when the
output of the integrating circuit 45 reaches said light modulating
level LV. Upon receiving said light emission stop signal in a step
S22, the CPU 31 controls the light emission control circuit 36 in a
step S23, thereby terminating the main light emission, and then
terminates the sequence.
According to the above-explained procedure, the step S14 extracts
the effective light metering areas based on the light metering
signals obtained at the preliminary light emission, the aperture
value and the phototaking distance, then the step S15 determines
the reflection factor distributions in said effective light
metering areas, and the step S16 determines the light modulating
level according to said refection factor distributions and the
number (size) of the effective light metering areas. At the main
light emission, it is terminated when the sum of the light metering
signals reaches said light modulating level.
As the effective light metering areas are determined in
consideration of the aperture value and phototaking distance at the
preliminary light emission, an appropriate light modulating level
can always be obtained regardless of the exposure conditions at the
phototaking operation or of the distance to the main object.
Therefore, the main object can be flash photographed with an
appropriate exposure, even in the presence of a highly reflective
article in the object field.
Also the variation of the light modulating level according to the
number (size) of the effective light metering areas provides
following advantages.
When the number of the effective light metering areas is few, the
sum of the light metering signals at the main light emission
(output of the integrating circuit 45) becomes smaller than in a
case where said number is larger. If the light modulating level is
taken constant regardless of said number, the main object tends to
be over or under exposed respectively if said number is smaller or
larger. The probability of attaining an appropriate exposure for
the main object becomes higher by decreasing or increasing the
light modulating level, as explained above, respectively when said
number of the effective light metering areas becomes smaller or
larger.
Also in the present embodiment, the light modulating level varies
according to the reflection factor distributions of the light
metering areas. Thus, for example, if the reflection factor
distribution of a light metering area containing the main object is
higher than that in other light metering areas (in such case the
main object tends to be over exposed), the light modulating level
is lowered according to the difference in said distributions, so
that the main object can be flash photographed with an appropriate
exposures. On the other hand, when the reflection factor
distributions are uniform, the light modulating level LV becomes
higher, thereby preventing under exposure. Furthermore, if the
determined light modulating level is lower than a predetermined
value, it is corrected to said predetermined value, thereby
preventing the underexposure situation resulting from an
excessively low light modulating level.
In the camera of the foregoing embodiment capable of a preliminary
light emission and a main light emission, the effective light
metering areas are extracted from the plural light metering areas
based on the light metering signals obtained at the preliminary
light emission and the diaphragm aperture and phototaking distance
of the phototaking lens at said preliminary light emission. The
main light emission is terminated according to the light metering
signals obtained in said effective light metering areas. It is
therefore rendered possible to exactly act the effective light
metering areas regardless of the diaphragm aperture and phototaking
distance of the phototaking lens at the preliminary light emission,
and to effect the light modulation without the influence of the
light metering signals resulting, for example, from a highly
reflective article or an article closer than the main object,
thereby reliably giving an appropriate exposure to the main
object.
Also in the camera capable of a preliminary light emission and a
main light emission, the light modulating level for terminating the
main light emission is determined according to the reflection
factor distributions of the light metering areas obtained in the
preliminary light emission, so that the main object can always be
flash photographed with an appropriate exposure, regardless of the
levels of the reflection factor distributions.
In the following there will be explained a second embodiment of the
present invention with reference to FIG. 16. In the foregoing
embodiment, the light modulating level LV is determined according
to the reflection factor distributions Rn of the light metering
areas and the number (size) M of the effective light metering
areas, but it may also be determined by said number, disregarding
said distributions. In such case, the procedure for calculating the
reflection factor distributions shown in FIG. 13 is omitted, and
the steps S1602-S1608 in FIG. 14 are modified as shown in FIG. 16.
In this case the light modulating level LV is defined by
0.02.times.M, and is determined solely by the number (size) of the
effective light metering areas.
In the camera of the present embodiment capable of a preliminary
light emission and a main light emission, the effective light
metering areas are extracted according to the light metering signal
obtained at the preliminary light emission, and the light
modulating level is determined according to the size of said areas,
so that the probability of flash photographing the main object with
an appropriate exposure is significantly higher than in the
conventional camera in which the light modulating level is
constant.
In the following there will be explained a third embodiment of the
present invention with reference to FIG. 17. In the foregoing
embodiments there has been explained a correction of the light
modulating level to a predetermined value if said level is lower
than said value. In the embodiment shown in FIG. 17, the light
modulating level is corrected to a predetermined value or lower if
it is higher than said predetermined value.
In FIG. 17, the steps S1605 and S1606 in FIG. 14 are changed to
steps S2001 and S2002, and steps S2003 and S2004 are added between
the steps S1607 and S1608. Thus, if the discrimination in the step
S1604 turns out affirmative, the step S2001 increases the light
modulating level LV by 0.025 (0.02 in case of FIG. 14), and, if
said discrimination turns out negative, the step S2002 increases
said level by 0.025.times.Rn/MAX(R). Thus the determined light
modulating level will have a maximum value of 0.125. Then the step
S2003 discriminates whether the light modulating level is at
maximum equal to 0.1, and, if so, the sequence proceeds to the step
S1608 but, if not, the sequence proceeds to the step S2004 to
correct the light modulating level to 0.1.
In the camera of the present embodiment cable of a preliminary
light emission and a main light emission, since the light
modulating level is determined from the light metering signals
obtained at the preliminary light emission, so that the probability
of giving an appropriate exposure to the main object at the flash
photographing operation is higher than in the conventional camera
in which the light modulating level is taken constant. Said
probability is further increased since the determined light
modulating level is corrected to a predetermined range if it is
outside said range.
The above-explained procedure limits the light modulating level
within a range of 0.03-0.1. Consequently, in addition to the
aforementioned advantages, there is further obtained an advantage
of preventing an overexposure resulting from an excessively high
light modulating level.
In the foregoing embodiments, the light modulating level is
regulated to obtain an appropriate exposure, but similar effects
can be also obtained by suitably varying the gain of the
integrating circuit 45 or the amplifiers 41a-41e (FIG. 9) for
processing the light metering signals obtained at the main light
emission, according to the light metering signals obtained from the
effective light metering areas at the preliminary light emission.
Consequently the determination of the light modulating level used
in the present specification includes such regulation of the gain
of the integrating circuit or the amplifiers. In such case, the
light modulating level is maintained constant at the main light
emission, while the light metering signals of the light metering
areas are synthesized through the integrating circuit or the
amplifiers of the gains determined as explained above, and the main
light emission is terminated when said synthesized output reaches
said constant light modulating level.
Though the foregoing embodiments have been limited to cameras
capable of preliminary light emission, the present invention is
likewise applicable to a camera without preliminary light emission.
In such case the effective light metering areas are extracted
according to the light metering signals obtained at an initial
stage of the main light emission. Then the light modulating level
or the weights are determined according to the light metering
signals obtained in said effective light metering areas, and the
light emission is terminated based on these data and the light
metering signals obtained after said initial stage.
It is also possible to extract the effective light metering areas
according to the light metering signals obtained in an initial
stage of the (main) light emission, to determine the light
modulating level as explained before according to the size (number)
of said effective light metering areas, and to terminate the light
emission when the light modulation evaluation factor, cumulatively
calculated from the light metering signals obtained after said
initial stage of the light emission, reaches said determined light
modulating level.
It is furthermore posse to calculate the reflection factor
distributions of the light metering areas based on the light
metering signals obtained in an initial stage of the (main) light
emission, then to determine the light modulating level as explained
before according to thus calculated reflection factor
distributions, and to terminate the light emission when the light
modulation evaluation factor, cumulatively calculated from the
light metering signals obtained after said initial stage of the
light emission, reaches said determined light modulating level.
It is furthermore possible to determine the light modulating level
according to the light metering signals obtained in an initial
stage of the (main) light emission, to correct said light
modulating level to a predetermined range, as explained before, if
said level is outside said range, and to terminate the light
emission when the light modulation evaluation factor, cumulatively
calculated from the light metering signals obtained after said
initial stage of the light emission reaches said determined or
corrected light modulating level.
In the foregoing embodiments, the light modulating level is
regulated to obtain an appropriate exposure, but similar effects
can be also obtained by suitably varying the gain of the
integrating circuit 45 or the amplifiers 41a-41e (FIG. 9) for
processing the light metering signals obtained in the main light
emission, according to the light metering signals obtained from the
effective light metering areas in an initial stage of the light
emission. Consequently the determination of the light modulating
level used in the present specification, includes such regulation
of the gain of the integrating circuit of the amplifiers.
In the foregoing embodiments, the light modulating level LV is
determined from the reflection factor distributions Rn of the light
metering areas and the number (size) of the effective light
metering areas, but there will be explained in the following an
embodiment of determining the light modulating level based solely
on the reflection factor distributions, disregarding said number M.
In this case the subroutine in FIG. 12 is omitted, and the
reflection factor distributions Rn for all the five light metering
areas are determined by the subroutine shown in FIG. 13. Thus all
the five areas are used as the effective areas. Consequently the
value 1/M in the step S1604 in FIG. 14 is fixed as 0.2, so that the
light modulating level LV is determined solely by the reflection
factor distributions of the areas.
Also the extraction of the effective light metering areas is
conducted in consideration of the aperture value and phototaking
distance in addition to the light metering signals at the
preliminary light emission, but said extraction may also be
conducted according to said light metering signals only.
Furthermore, the foregoing explanation has been limited to cameras
utilizing a silver halide-based photographic film, but the present
invention is likewise applicable for example to an electronic still
camera utilizing a floppy disk.
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