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Description  |
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BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a camera having a variable photographing
aperture and a control method thereof.
This application is related to the commonly assigned application U.S.S.N.
672,901, the disclosure of which is expressly incorporated by reference
herein.
2. Description of Related Art
Cameras in which a photographing aperture can be changed between a standard
size (i.e., full size) and a laterally elongated size (i.e., panoramic
size) are becoming popular. Cameras employing a photographing aperture
changing mechanism are usually provided with a program shutter, in which
exposure factors are automatically set in accordance with the brightness
of an object to be photographed. However, in conventional cameras, there
is no relationship between the setting operation of the exposure factors
and the changing operation of the photographing aperture.
If the setting operation of the exposure factors were to be associated with
the changing operation of the photographing aperture, a picture could be
photographed which satisfactorily reflects a photographer's intention. In
a known camera having a photographing aperture changing mechanism, a
panoramic size picture of an object can be photographed which has a
lateral length longer than the standard size picture. Accordingly, a
photographer can accommodate a scene that is much wider than it is high.
Such a picture may include only objects that are located in an infinite
object distance range, but usually includes objects located at various
distances. For example, large number of people are to be photographed,
they may all be located at substantially the same distance, but are
usually located at different distances. Under such circumstances, it is
preferable that the exposure factors are set so that the depth of field
for the panoramic photographing aperture is deeper than the depth of field
for the standard photographing aperture.
SUMMARY OF THE INVENTION
The primary object of the present invention is to provide a camera having a
variable photographing aperture in which the exposure factors can be
automatically controlled in association with the selected photographing
aperture size.
To achieve the object mentioned above, according to the present invention,
a camera having a variable photographing aperture is provided with means
for changing the size of the photographing aperture, means for calculating
exposure factors, including a diaphragm value and a shutter speed, in
accordance with brightness of an object to be photographed, and an
exposure adjusting device for adjusting the exposure factors when the
photographing aperture is changed by the photographing-aperture changing
device.
Preferably, a large photographing aperture and a smaller elongated
photographing aperture are provided. The elongated photographing aperture
is defined by the large photographing aperture in which upper and lower
portions thereof have been covered.
When the photographing aperture is changed from, the large size to the
small Size, the exposure adjusting device varies the exposure factors so
as to increase the depth of field.
Preferably, the exposure calculating means and the exposure adjusting means
determine an optimum exposure using different programs for the shutter
speed and aperture at the large photographing aperture and the small
photographing aperture.
In a preferred embodiment, the exposure adjusting means sets a large
diaphragm value so that the depth of field is greater than a predetermined
depth of field when the photographing aperture is changed from the large
size to the small size by the photographing aperture changing device.
The small diaphragm value is preferably larger than F8, and more preferably
larger than F11.
A lens having a variable focal length is also provided, as well as a focal
length modifying device for setting the focal length of the lens to a
specific focal length on a short focal length side when the photographing
aperture is changed from the large size to the small size by the
photographing aperture changing device.
According to another aspect of the present invention, a camera having a
variable photographing aperture includes a photographing aperture changing
device changing the photographing aperture between a standard size and a
panoramic size, means for detecting the size of the photographing aperture
selected by the photographing aperture changing device, and an exposure
calculating means for determining a diaphragm value and shutter speed in
accordance with brightness of an object to be photographed. The camera
further includes an exposure adjusting device for adjusting a combination
of the diaphragm value and the shutter speed determined by the exposure
calculating device to a combination of a diaphragm value larger than the
diaphragm value determined by the exposure calculating device and a
shutter speed corresponding to the adjusted diaphragm value when the
photographing aperture is changed from the standard size to the panoramic
size by the photographing aperture changing device.
According to still another aspect of the present invention, a control
method of a camera having a variable, photographing aperture and an
exposure calculating device for determining exposure factors, including a
diaphragm value and a shutter speed, in accordance with a brightness of an
object to be photographed, is provided. The control method includes a
first step in which, when the photographing aperture is changed from the
standard size to the laterally elongated size, it is assumed that a
photographer wants to set exposure factors in a manner such that an
increased depth of field is defined. A second is included in which the
exposure factors are adjusted to increase the depth of field in accordance
with the assumption in the first step.
The present disclosure relates to subject matter contained in Japanese
Utility Model Application No. HEI 4-5176 (filed on Feb. 12, 1992) which is
expressly incorporated herein by reference in its entirety.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be described below in detail with reference to
the accompanying drawings, in which;
FIG. 1 is a block diagram of a main part of a camera having a variable
photographing aperture, according to the present invention;
FIG. 2 is a flow chart of a main operation of the variable photographing
aperture camera shown in FIG. 1;
FIG. 3 is a program diagram of the variable photographing aperture camera
shown in FIG. 1;
FIGS. 4A and 4B are explanatory views of the variable photographing
aperture and a light intercepting plate in different operational
positions; and,
FIGS. 5A and 5B are conceptual views of a photographing aperture changing
mechanism shown in a panoramic position and a standard position,
respectively.
DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 is a block diagram showing main components of a variable
photographing aperture camera to which an embodiment of the present
invention is applied. A photographing aperture changing means 10 is
adapted to change the photographing aperture between a full size (i.e.,
standard size of about 35 mm.times.24 mm) and a panoramic size in which
the dimension of height is decreased. The photographing aperture changing
means 10 includes, for example, a pair of movable light intercepting
plates 30 which partly cover a predetermined portion of upper and lower
edges of a photographing aperture 25, to partly intercept light incident
thereon, so that the size of the photographing aperture can be adjusted or
varied by the movement of the light intercepting plates 30, as can be seen
in FIGS. 4A and 4B. Alternatively, it is possible to expose predetermined
portions on the upper and lower edges of a picture frame to define the
panoramic size picture frame upon panoramic photography. Moreover, it is
also known to provide a small discriminating unexposed area or exposed
area in the vicinity of a panoramic picture frame that can be detected by
an automatic printer of a laboratory. The camera is provided on the camera
body with a photographing aperture selecting switch 11, such as a slidable
switch or push button, which can be manually actuated by a photographer to
actuate the photographing aperture changing means 10.
FIGS. 5A and 5B show a photographing aperture changing means 10 for
mechanically switching the size of the photographing aperture between the
normal and panoramic photographing positions. A camera body 26 has a
photographing aperture 25 which defines the size of film frame upon taking
a standard size picture.
A pair of light intercepting plate guides 29 are provided on the upper and
lower sides of the aperture 25, respectively, on the front surface of the
body 26. The light intercepting plate guides 29 guide a pair of upper and
lower light intercepting guide plates 30 so as to move up and down (i.e.,
in the vertical direction). The light intercepting plates 30 can occupy a
retracted position, in which the plates 30 are located out of the aperture
25, as shown in FIG. 5B, and an operative position, in which the plates 30
come into contact with stops 29a of the light intercepting plate guides
29, as shown in FIG. 5A. In the operative position, the light intercepting
plates 30 partially cover the upper and lower portions of the aperture 25
defining the panoramic aperture 25P.
The pair of light intercepting plates 30 are connected to leaf springs 31,
at the ends indicated 31a. The leaf springs 31 are secured to a pair of
upper and lower rack plates 32, at the ends indicated 31b. The rack plates
32 have racks 32a opposed to each other, so that the racks 32a are in mesh
with a common pinion 33 located therebetween. The rack plates 32 are
continuously biased away from one another by a tensile spring 34. Namely,
the light intercepting plates 30 are continuously biased towards the
retracted position. The outward movement of the rack plates 32, towards
the retracted position, is restricted by respective stops 35 provided on
the camera body 26. The elasticity of the leaf springs 31 ensures that the
light intercepting plates 30 come into contact with the respective stops
29a in the panoramic position shown in FIG. 5A and are retracted from the
aperture 25 at the normal shot position shown in FIG. 5B.
The pinion 33 is rotated by a motor 36 whose rotation is controlled by a
control means 40. The control means 40 drives the motor 36 in such a way
that, for example, when the photographing aperture changing switch is
switched to the panoramic position, a panoramic photographing aperture, as
shown in FIG. 5A, is defined, and when the photographing aperture changing
switch is switched to the standard position, a standard photographing
aperture, as shown in FIG. 5B, is defined.
A switch 12 for detecting the size of the photographing aperture is
provided above one of the stops 35 and is turned ON when the racks 32 are
moved to the panoramic position to detect the panoramic photographing
aperture.
Photographing aperture size detecting means 12 detects the size of the
photographing aperture (i.e., standard size or panoramic size) which is
controlled by the photographing aperture changing means 10. To this end,
the camera body is provided with a switch or the like, that is associated
with the operation of the photographing aperture changing switch 11
provided on the camera body to actuate the photographing aperture changing
means 10. Alternatively, in the case where the photographing aperture
changing means 10 is comprised of the light intercepting plates 30, it is
also possible to provide switches or sensors, etc., in the vicinity of the
light intercepting plates 30.
A photometering means 13 detects the brightness of an object to be
photographed and transmits the brightness data to an exposure calculating
means 15. The photometering means 13 is comprised of, for example, a light
receiver provided on the camera body to measure the object brightness, as
is well known.
A film sensitivity discriminating means 14 detects sensitivity data of a
photographing film to be used and transmits the film sensitivity data to
the exposure calculating means 15. Film sensitivity can be discriminated,
for example, by DX codes provided on a side face of a patrone of a 35 mm
film. The DX codes are read by a plurality of contact pins provided in a
patrone loading chamber of the camera body to come into contact with the
DX codes. Alternatively, it is possible to provide a selection button or
the like on the camera body, so that the selection button is manually
actuated by a photographer to directly detect the film sensitivity.
The exposure calculating means 15 calculates a diaphragm value and a
shutter speed in accordance with the brightness data sent from the
photometering means 13 and the film sensitivity data sent from the film
sensitivity discriminating means 14. The calculation of the exposure
calculating means 15 can be carried out, for example, by a micro-computer,
etc.
An exposure adjusting means 16 adjusts or modifies the diaphragm value and
the shutter speed determined by the exposure calculating means 15, so that
the depth of field increases, in accordance with the detection results of
the photographing aperture size detecting means 12 when the panoramic
photographing aperture is selected. In practice, the diaphragm value
calculated by the exposure calculating means 15 is replaced with a larger
diaphragm value in the adjustment or correction operation, and a shutter
speed corresponding to the adjusted diaphragm value is then calculated.
The diaphragm value and the shutter speed thus corrected are fed to a
diaphragm control mechanism 18 and a shutter mechanism 17, per se known,
respectively. The correction effected by the exposure adjusting means 16
is carried out in accordance with the program diagram shown in FIG. 3. The
diagram 20 corresponds to the standard photographing aperture and the
diagram 21 corresponds to the panoramic photographing aperture.
As can be seen in FIG. 3, in the correction operation by the exposure
adjusting means 16, when the panoramic photographing aperture is selected,
1 APEX value is added to the Av value of the standard photographing
aperture size, and 1 APEX value is subtracted from the Tv value of the
standard photographing aperture size. The calculation in the exposure
adjusting means 16 is carried out, for example, by a micro computer. It is
possible to provide a single exposure controller 19 in which both the
calculations of the exposure calculating means 15 and the exposure
adjusting means 16 are effected by the same micro computer.
FIG. 2 shows a flow chart of a main operation of the variable photographing
aperture camera according to the present invention.
When the photometering switch, associated with a release button provided on
the camera body, is turned ON, control proceeds to step S1, in which the
exposure calculating means 15 determines the diaphragm value and the
shutter speed in accordance with the brightness data and the film
sensitivity data fed from the photometering means 13 and the film
sensitivity discriminating means 14, respectively. Thereafter, control
proceeds to step S2.
At step S2, the photographing aperture size detecting means 12 checks
whether the photographing aperture is panoramic size or standard size. If
the standard photographing aperture has been selected, the diaphragm value
and the shutter speed are not adjusted by the exposure adjusting means 16.
Namely, the calculated diaphragm value and the corresponding shutter speed
are output to the diaphragm control mechanism 18 and the shutter mechanism
17. Conversely, if at step S2 the panoramic photographing aperture has
been selected, control proceeds to step S3.
At step S3, the exposure adjusting means 16 switches from the program
diagram 20, for determining exposure values at the standard photographing
aperture, to program diagram 21 for determining exposure values at the
panoramic photographing aperture. The diaphragm value and the shutter
speed determined by the exposure calculating means 15 are adjusted by
adding 1 APEX value to the Av value corresponding to the diaphragm value
and by subtracting 1 APEX value from the Tv value corresponding to the
shutter speed. Consequently, the adjusted diaphragm value and shutter
speed are fed to the diaphragm control mechanism 18 and the shutter
mechanism 17.
The APEX value added to the Av value and subtracted from the Tv value is
not limited to 1 and can be any value.
It is possible to set an optimum diaphragm value, in the panoramic
photographing aperture position, to a size larger than a predetermined
specific diaphragm value (e.g., F11), so that a shutter speed
corresponding to the set diaphragm value can be calculated. Furthermore,
in the case that a picture of objects located at the same distance is
taken using a zoom lens, the depth of field at the object distance is
deeper when a short focal length (e.g., 28 mm) of the taking lens (i.e.,
zoom lens) is set, than when a long focal length (e.g., 50 mm) is set.
Therefore, it is advantageous to replace the F value with a larger F value
(i.e., small diaphragm value), taking the focal length data into account,
when a zoom lens is used as the taking lens.
As can be understood from the above discussion, according to the present
invention, the depth of field can be automatically increased when the
panoramic photographing aperture is selected, without a need for the
photographer to manually adjust the exposure factors. Consequently, since
a photographer typically makes such a depth of field adjustment when
taking panoramic pictures, the present invention has provided a variable
photographing aperture camera in which the photographer is relieved of
this operation.
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