JP2544145B2 - camera - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to a camera, and more particularly, to a photographing lens,
A pan-focus camera or a zone-focus camera having an aperture and a shutter, a distance measuring device, and a photometric device,
By providing a film sensitivity switching device and a flash light emitting device,
Like a conventional autofocus camera, which is configured so that the aperture can be set according to the subject distance obtained by the distance measuring device and the flash light emitting device is operated so as to obtain an appropriate exposure when necessary. The present invention relates to an inexpensive camera with a simple structure that does not use an expensive taking lens drive mechanism having a complicated structure and can guarantee the same shooting accuracy as a conventional autofocus camera.

2. Description of the Related Art A conventional pan-focus camera or zone-focus camera has a simple structure and is inexpensive, but it suffers from the drawback of poor photographing accuracy. On the other hand, the conventional autofocus camera is easy to operate and has good shooting accuracy, but it requires a mechanism with a complicated structure such as a shooting lens drive mechanism for setting the shooting distance in the shooting lens in conjunction with the distance measuring device. , Was inevitably expensive.

An object of the present invention is to use a photographing lens driving mechanism or the like having a complicated and expensive structure such as a conventional autofocus camera, to have a simple structure and low cost, and to obtain a photographing accuracy equivalent to that of a conventional autofocus camera. An object of the present invention is to provide a camera provided with the obtained flash light emitting device.

SUMMARY OF THE INVENTION The object of the present invention is to transform a photographing lens in which a focusing distance to a subject is fixed in advance, a diaphragm device that also serves as a shutter, and a voltage corresponding to a driving source of the diaphragm device. The resulting bimorph piezoelectric element, a distance measuring device that measures the distance to the subject, a photometric device that measures the field brightness, a film sensitivity switching device that selects according to the film used, a flash light emitting device, and the above-mentioned shooting A set shooting distance signal representing the set shooting distance set on the lens, a subject distance signal representing the subject distance detected by the distance measuring device, and a film sensitivity signal representing the film sensitivity set by the film sensitivity switching device are input. Aperture calculation time that outputs a set aperture value signal that indicates an aperture value such that the subject position is within the depth of field of the taking lens. And a bimorph that acts to close the lens aperture by deenergizing and holding the aperture device at that time by opening the aperture device by energizing the voltage and stopping the energization. An aperture drive circuit for driving a piezoelectric element, a control circuit whose output is connected to the aperture drive circuit and which outputs a drive signal for holding the aperture device at the set aperture value, and an output drive signal of the control circuit are input. And a drive circuit driven by the drive circuit, the output of the drive circuit is connected to the aperture drive circuit, and the aperture drive circuit is configured so that the bias drive of the aperture drive circuit is stopped by the output drive signal of the drive circuit. And a film sensitivity signal from the film sensitivity switching device is input, and a set time signal representing the set time corresponding to the film sensitivity signal is calculated. A time setting circuit, and the minimum proper exposure permissible luminance signal representing the minimum proper exposure permissible luminance obtained based on the set aperture value signal and the set second signal by inputting the set aperture value signal and the set second signal. And a timer connected to the diaphragm drive circuit to deactivate the diaphragm drive circuit by inputting the set time signal to output a lens aperture closing signal. An OR circuit for inputting the output drive signal from the camera and a lens aperture closing signal from the timer, and the minimum proper exposure permissible brightness signal from the set brightness calculation circuit and the subject brightness signal near the photometric device. And a comparator circuit that outputs a flash light emission signal for operating the flash light emitting device when the former is large, and the input is the output of the OR circuit and the ratio. An AND circuit connected to the output of the circuit, the output of which is connected to the flash light emitting device, and the guide number of the flash light emitting device is input to the aperture calculation circuit, and the input is performed. If the aperture number corresponding to the set guide number calculated from the guide number, the set film sensitivity, and the distance measurement value detected by the distance measuring device is smaller than the set aperture value, the setting is performed. The shooting is performed with the aperture number corresponding to the guide number, and the flash light emitting device is activated in the guide number control aperture during opening of the set aperture device to the set aperture value or during closing after opening. In this case, photographing is performed with the set aperture value, and the aperture calculation circuit is configured to operate the flash light emitting device, φ is accomplished by the permissible circle of confusion F is obtained by the camera aperture f at the time when the circle of confusion diameter becomes φ satisfying the focal length L _e is set photographing distance L subject distances ranging photographic lens.

In the present invention, as the diaphragm driving circuit, a bimorph piezoelectric element or the like is used, and when a voltage is applied to the bimorph piezoelectric element, the diaphragm is actuated by utilizing the deformation of the bimorph piezoelectric element corresponding to this voltage. Advantageously, a bimorph drive circuit is utilized.

In this case, it is possible to use a diaphragm / shutter in which the diaphragm and the shutter are integrated, and in that case, the closing operation starts immediately before or after the diaphragm reaches the set diaphragm value in relation to the calculated exposure time, or Alternatively, when the set aperture value is reached, the energization may be stopped so that the aperture is kept at this set aperture value and the closing operation is started after a predetermined time.

Further, it is also possible to simplify the drive circuit by holding the aperture control stepwise instead of making it continuous as is well known.

In the present invention, not only the lens shutter but also a focal plane shutter can be used.

Since it is configured as described above, in the present invention,
The aperture is operated by the aperture drive circuit, and the aperture position is set to the set aperture value that is set so that the subject position obtained by the aperture calculation circuit is within the depth of field of the shooting lens based on the detected subject distance. When the exposure time reaches, the control circuit can perform exposure with the aperture limited to the set aperture value with the exposure time according to the field brightness detected by the photometric device at that time, and the field brightness is set. When the brightness is less than the minimum proper exposure allowable brightness set by the brightness calculation circuit, the flash light emitting device can be operated to obtain a proper exposure, so a complicated and expensive photographing lens drive mechanism like a conventional autofocus camera is not used. With the simple and inexpensive camera according to the present invention, the aperture can be simply limited to the set aperture value and the exposure time according to the field brightness can be taken.
Since the subject position is always within the depth of field, it is possible to obtain an excellent effect that photography is always possible with excellent precision equivalent to that of an expensive autofocus camera having a complicated structure in the related art.

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 1 shows a preferred embodiment of a camera according to the present invention when a shutter that also serves as an aperture is used.

A signal 2 representing the set shooting distance of the photographing lens 1 and a subject distance signal 4 representing the distance measured from the distance measuring device 3 are input to the aperture calculation circuit 5, and the subject position corresponds to the set film sensitivity of the photographing lens 1. Calculates the aperture value set so that it is within the depth of field, and also calculates the appropriate aperture value for the exposure amount from the set film sensitivity signal 22 from the film sensitivity switching device 21, the subject distance signal 4, and the guide number. Then, the smaller aperture area is selected as the set aperture value and the set aperture value signal 6 is output.

How to obtain the above-mentioned aperture value setting is the focal length f of the photographing lens 1 as shown in FIG. 2, the permissible circle of confusion diameter for obtaining a set is set to the photographing lens 1 shooting distance L _e and good resolution It utilizes the fact that the aperture value can be set from φ so that the subject position is within the depth of field of the taking lens.
That is, when the photographing lens 1 is set to the set photographing distance L _e , if the diaphragm is set to the minimum diaphragm value F _max , the closest photographing distance becomes the shortest photographing distance L ₁ as shown in FIG.
It is possible to shoot with good resolution in a wide range up to infinity, but if you set the aperture to a large aperture value F _min , the closest shooting distance L ₂ will result, as shown in the drawing. It is possible to perform shooting with a good resolution only up to a distance farther than the shortest shooting distance L ₁ , and the shooting distance L ₂ ′ with a good resolution on the far side is significantly shortened. If the object distance measured is L, the diameter of the circle of confusion is the diameter of the permissible circle of confusion φ
The aperture value F can be derived by the following equation.

If shooting is performed with an aperture having an aperture smaller than the aperture value F calculated here, it is possible to perform shooting with a desired resolution.

On the other hand, in the present invention, when a bimorph drive circuit having a bimorph piezoelectric element 8 is used, the diaphragm drive circuit 7 includes a booster circuit 9 for energizing the bimorph piezoelectric element 8, and this bimorph piezoelectric element 8 gives a voltage. A pair of symmetrically arranged and symmetrically actuated elements which, when actuated, actuate a diaphragm blade drive member 11 pivotally pivoted by a pivot point 10 when actuated. Diaphragm blade
The apertures 12 and 12 'are opened in correspondence with the amount of movement of the diaphragm blade drive member 11 to form a diaphragm aperture in the lens aperture 13. One of the diaphragm blades 12 'is provided with a diaphragm opening signal input unit 14, which inputs a signal 16 corresponding to the diaphragm opening to a counter 17 by an encoder 15 and corresponds to the diaphragm opening from this counter 17. It is connected to output a pulse signal 18.

The output setting aperture value signal 6 from the aperture calculation circuit 5 is input to one input of the comparison circuit 42 described later. The other input of the comparison circuit 42 is input with the output 41 of the exposure calculation circuit 40 that adds the output 32 of the photometric device 31 and the output 24 of the time setting circuit 23. The comparison circuit 42 outputs the output 6 of the aperture calculation circuit 5 here.
And the output 41 of the exposure calculation circuit 40 are compared, and the smaller aperture value is selected and its output 43 is output. Output of comparison circuit 42
The throttle opening pulse signal 18 corresponding to the throttle opening from the counter 43 and the counter 17 is input to the control circuit 19 and compared with the actual throttle opening pulse signal 18 representing the opening of the throttle operated by the diaphragm drive circuit 7. When the small aperture value 43 selected by the circuit 42 matches, the control circuit 19 generates the control signal 20, which drives the drive circuit 29, and the output drive signal 30 of the drive circuit 29 is input to the aperture drive circuit 7. The aperture opening set by the bimorph piezoelectric element 8 is held at the aperture value set by the aperture calculation circuit 5, or before or after reaching the aperture value related to the field brightness as described later. Will close the lens opening immediately.

When the diaphragm is controlled stepwise as described above, the diaphragm opening is always set smaller than the set diaphragm value.

The set film sensitivity signal 22 of the film sensitivity switching device 21 is also input to the second setting circuit 23 and outputs the second signal 24 corresponding to the set film sensitivity. The setting time signal 24 is connected so as to be input to a setting brightness calculation circuit 25 for inputting the output setting aperture value signal 6 of the aperture calculation circuit 5 and a timer 26. In this way, the set brightness calculation circuit 25 calculates the set minimum appropriate exposure allowable brightness so as to give the minimum appropriate exposure allowable brightness corresponding to the set aperture value and the set second based on the set aperture value and the set second. The timer 26 outputs the lens aperture closing signal 28 for closing the lens aperture based on the set time signal 24 while outputting the setting proper exposure permissible luminance signal 27. The setting minimum proper exposure permissible luminance signal 27 from the above-mentioned set luminance calculation circuit 25 is connected so as to be inputted to the comparison circuit 33 which inputs the photometric value signal 32 representing the field luminance from the photometric circuit 31. The set minimum proper exposure allowable brightness signal 27 and the photometric value signal 32 are compared, and when the former is large, a flash light emission signal 35 for operating the flash light emission device 34 is output as described later. Output control signal of the control circuit 19 described above
20 is also connected to one input of an OR circuit 36, the other input of which is connected to receive the output lens aperture close signal 28 from the timer 26. Furthermore, the output signal 37 of the OR circuit 36 and the output signal 35 of the comparison circuit 33 are connected to the input of an AND circuit 38, and the AND circuit 38
Is connected to the flash light emission circuit 34 described above. The flash light emitting circuit 34 may be activated by the boosting circuit 9 which activates the diaphragm driving circuit 7.

With this configuration, when the camera is released, the subject calculated by the aperture calculation circuit 5 based on the set shooting distance signal 2, the distance measuring device 3 and the output signals 4 and 22 of the film sensitivity switching device 21. A set aperture value signal 6 whose position is within the depth of field range is obtained, and this set aperture value signal 6 is input to the set brightness calculation circuit 25 and set by the output signal 22 of the film sensitivity switching device 21. Signal 24 per second set corresponding to film sensitivity
Is input to the set brightness calculation circuit 25 to output the set minimum proper exposure allowable brightness signal 27, and the set time signal 24 is input to the timer 28 to output the lens aperture closing signal 28. The output of the timer 26 is the diaphragm drive circuit 7
Connected to the transistor 39 of the timer 26, the aperture drive circuit 7 is deenergized by the output signal 28 from the timer 26 to close the lens aperture, and the output signals 27 and 32 of the set brightness calculation circuit 23 and the photometry circuit 31 are compared with each other. 33, and if the former is larger, the comparison circuit 33 sends a flash signal.
35 is output and input to one input of the AND circuit 38. On the other hand, the output of the OR circuit 36 for inputting the output signals 28 and 20 of the timer 26 and the control circuit 19 is connected to the other input of the AND circuit 38, and the output of the AND circuit 38 is the flash light emitting device.
Since it is connected to the input of 34, when the set luminance signal 27 is larger than the actual luminance signal 32 representing the actual luminance from the photometric device 31, in the state where the flash light emission signal 35 is output from the comparison circuit 33. When either the drive signal 20 from the control circuit 19 or the output signal 28 from the timer 26 is output, the OR circuit 36 generates an output and the AND circuit 38 activates the flash light emission circuit 34. It produces a flash of light.

When the set luminance signal 27 is smaller than the actual luminance signal 32, the AND circuit 38 does not output because the comparison circuit 33 does not output, so normal proper exposure shooting is performed in a state where the flash light emitting device 34 is not operated. Do it.

In the present invention, the guide number of the flash light emitting device is input to the aperture calculation circuit, the input guide number, the set film sensitivity, and the distance measuring device detected by the distance measuring device. The aperture value corresponding to the set guide number is calculated from the value and, when the aperture value corresponding to the set guide number is smaller than the set aperture value, shooting is performed with the aperture value corresponding to the set guide number and the flash light emitting device is operated. The aperture calculation circuit can be configured as described above.

Further, the guide number of the flash light emitting device is inputted to the aperture calculation circuit, and the set guide number is obtained from the inputted guide number, the set film sensitivity and the distance measuring value detected by the distance measuring device. A corresponding aperture value is calculated, and when the corresponding aperture number corresponding to the set guide number is larger than the set aperture value, shooting is performed at the set aperture value, and the aperture calculation circuit is arranged to disable the flash light emitting device. Can be configured.

Furthermore, in the present invention, the guide number of the flash light emitting device is inputted to the aperture calculation circuit, and the inputted guide number, the set film sensitivity, and the distance measuring device detect the guide number. The aperture value corresponding to the set guide number is calculated from the distance measurement value, and when the aperture value corresponding to the set guide number is smaller than the set aperture value, the aperture is being opened to the set aperture value or being closed after being opened. The aperture calculation circuit may be configured to operate the flash light emitting device with the aperture value corresponding to the setting guide number.

In the illustrated embodiment, the shutter is a shutter that also serves as an aperture, so as described above, the closing operation is started immediately before or after the aperture reaches the set aperture value according to the field brightness and the set film sensitivity. Alternatively, the closing operation is started after the required time is maintained at the set aperture value.

In the above description, the shutter that also serves as the diaphragm is used, but not limited to the shutter that also serves as the diaphragm, another type of lens shutter and diaphragm, or a focal-plane shutter can be used.

The operation of the camera of the present invention can be understood from the above description.

As described above, according to the camera of the present invention, all the photographed subjects are within the depth of field of the photographing lens and can photograph with good resolution, and the field brightness is lower than the set minimum proper exposure permissible brightness. When it is small, the flash circuit is activated, so you can always get the proper exposure.
Even if a conventional structure is complicated and an expensive auto-focus camera is not used, by setting the above-mentioned aperture value with a simple structure and an inexpensive camera according to the present invention, performance equivalent to that of a conventional auto-focus camera can be obtained. It can be demonstrated.

As described above, the aperture value may be continuously controlled, and the aperture value may be controlled to be held in stages in order to simplify the structure and reduce the manufacturing cost, and in that case,
The image is taken with an aperture value smaller than the calculated set aperture value.

In order to clarify the excellent performance of the present invention, the performance of a camera that controls the aperture based on the distance measured by the distance measuring device to perform shooting according to the present invention and a conventional pan-focus camera or zone-focus camera is described. Let's compare and see.

For example, when shooting with a normal pan-focus camera with a focal length f = 35 mm and a minimum shooting distance of 1 m,
The permissible circle of confusion is 0.077 mm, and the shooting lens aperture is F8.
Assuming that the shutter speed is 1/60 seconds and the exposure tolerance is ± 2 EV, the set shooting distance is such that the permissible circle of confusion diameter is within 0.077 mm from the shortest shooting distance to the infinity distance in the hyperfocal distance, that is, the set shooting distance. Will be about 2m.

FIG. 3 shows the shooting conditions of the pan-focus camera, that is, the shooting lens focal length f = 35 mm, the set shooting distance = 2 m,
Set aperture value F8, permissible circle of confusion diameter 0.08 mm, shutter speed
6 is a drawing showing a light value and a shooting distance range with which a good resolution image can be obtained at 1/64 seconds. That is, the range from the shooting distance range of 1.02 m to the infinite distance can be taken only in the range of light value 10 to 14.

On the other hand, in the case of taking an image with proper exposure by using the set aperture value obtained by the distance measuring device and the photometric device according to the present invention, as shown in FIG.
35 mm, set shooting distance L ₀ = 2.5 m, and permissible circle of confusion 0.08 mm, the change range of the diaphragm becomes F4 to F22, and the shooting distance range with good resolution is 0.58 m to infinity and the light value is 8 to 17. You can shoot in the range.

As is clear from comparing FIGS. 3 and 4, according to the present invention, the photographing performance is significantly better than that of the conventional pan-focus camera, and the photographing performance of the present invention as shown in FIG. However, it has excellent shooting performance comparable to that of a complicated and expensive conventional autofocus camera.

FIG. 5 shows the light value and the shooting distance range that enable good shooting when the permissible circle of confusion diameter is 0.04 mm in the case of the conventional pan-focus camera similar to FIG. That is, a shooting distance of 1.35 in the range of light value 10 to 14
Good shooting is possible only in the range of m to 4.00m.

Contrary to this, according to the present invention, as shown in FIG. 6, in the set aperture values F4 to F22, the set shooting distance is 2.5 m, the permissible circle of confusion diameter is 0.04 mm, and in the light value range is 8 to 17, the shooting distance is 0.93 m. Thus, it becomes possible to take an image in the range of infinity with a good resolution.

As described above, according to the present invention, a much better shooting performance than that of a normal pan-focus camera can be obtained, and such shooting performance is sufficiently comparable to that of an expensive auto-focus camera.

Although a pan focus camera has been described as an example in the above description, it is obvious to those skilled in the art that the present invention can be applied to a zone focus camera.

As described above, according to the present invention, the aperture is driven by the aperture drive circuit, and the subject position obtained by the aperture calculation circuit based on the detected distance is within the depth of field of the taking lens. When the aperture of the aperture is reached to the set aperture value that is set in a certain way, the control circuit limits the aperture to the set aperture value with an exposure time according to the field brightness detected by the photometric device at that time. The exposure can be performed, and when the field brightness is smaller than the minimum proper exposure allowable brightness set by the set brightness calculation circuit, the flash light emitting device can be operated to obtain the proper exposure. At the time of exposure according to the field brightness by simply limiting the aperture to the set aperture value with a camera having a simple and inexpensive structure according to the present invention without using a complicated and expensive photographing lens driving mechanism. Since the subject position is always within the depth of field, the structure is complex and expensive as in the past, and it is always possible to shoot with excellent accuracy comparable to that of an autofocus camera. Be done.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing the structure of a camera according to the present invention. FIG. 2 is a diagram showing the relationship between the aperture opening at the permissible circle of confusion diameter with respect to the set shooting distance of the shooting lens and the shooting distance that enables good shooting. FIG. 3 is a diagram showing an example of a photographing range that enables good photographing with a conventional pan-focus camera. FIG. 4 is a diagram similar to FIG. 3, but showing one example of a photographing range that enables favorable photographing when the set aperture value is changed according to the present invention. FIG. 5 is a diagrammatic view showing another example of a photographing range that enables favorable photographing in a conventional pan-focus camera. FIG. 6 is a diagram similar to FIG. 5, but showing another example of the photographing range that enables good photographing when the set aperture value is changed according to the present invention. 1 ... Shooting lens 2 ... Set shooting distance signal 3 ... Distance measuring device 4 ... Distance measuring signal 5 ... Aperture calculation circuit 6 ... Set aperture value signal 7 ... Aperture drive circuit 8 ... Bimorph piezoelectric element 9 …… Booster circuit 11 …… Aperture blade drive member 12, 12 ′ …… Aperture blade 13 …… Shooting lens aperture 14 …… Aperture aperture signal input unit 15 …… Encoder 17 …… Counter 18 …… Aperture aperture pulse Signal 19 …… Control circuit 21 …… Film sensitivity switching device 23 …… Second time setting circuit 25 …… Set brightness calculation circuit 26 …… Timer 29 …… Drive circuit 31 …… Photometer 33, 42 …… Comparison circuit 34 …… … Flash emission device 36 …… OR circuit 38 …… AND circuit 39 …… Transistor 40 …… Exposure calculation circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiyoshi Toma 2-16-20 Shimura, Itabashi-ku, Tokyo Copal Co., Ltd. (56) Reference JP-A-55-17187 (JP, A) JP-A-60-4929 (JP, A) JP-A-59-228636 (JP, A)

Claims (2)

(57) [Claims] 1. A photographing lens in which a focusing distance to a subject is made constant in advance, a diaphragm device which also serves as a shutter, and a bimorph which deforms in response to a voltage by applying a voltage as a driving source of the diaphragm device. Piezoelectric element, photometric device for measuring the field brightness, film sensitivity switching device selected according to the film used, flash emission device, and set shooting distance signal indicating the set shooting distance set for the shooting lens And a subject distance signal indicating the subject distance detected by the distance measuring device and a film sensitivity signal indicating the film sensitivity set by the film sensitivity switching device, and the subject position is within the depth of field of the taking lens. An aperture calculation circuit that outputs a set aperture value signal that represents a certain aperture value, and the aperture device that is activated by applying a voltage. A diaphragm drive circuit that drives the bimorph piezoelectric element that acts to close the lens opening by holding the diaphragm device at that time by stopping the biasing and holding the diaphragm device at that time by stopping the bias, and the output A control circuit that is connected to an aperture drive circuit and outputs a drive signal that holds the aperture device at the set aperture value; a drive circuit that is driven by inputting an output drive signal of the control circuit; and an output of the drive circuit Is connected to the diaphragm drive circuit, and the diaphragm drive circuit is configured so that the bias drive of the diaphragm drive circuit is stopped by the output drive signal of the drive circuit, and the film from the film sensitivity switching device. A second setting circuit for inputting a sensitivity signal and calculating a set second signal representing the set second corresponding to the film sensitivity signal; A setting brightness calculation circuit for inputting a setting time signal and outputting a minimum appropriate exposure allowable brightness signal that represents a minimum appropriate exposure allowable brightness obtained based on these set aperture value signal and setting time signal, A timer connected to the diaphragm drive circuit so as to deactivate the diaphragm drive circuit by inputting a second signal and outputting a lens aperture closing signal, and the output drive signal from the control circuit and the timer. An OR circuit for inputting a lens aperture closing signal, the minimum proper exposure permissible luminance signal from the setting luminance calculation circuit and a subject luminance signal closer to the photometric device are input and these signals are compared. When the former is large, A comparison circuit for outputting a flash emission signal for operating the flash emission device, an input connected to an output of the OR circuit and an output of the comparison circuit, and an output of the comparison circuit An AND circuit connected to the optical device, the guide number of the flash light emitting device is input to the aperture calculation circuit, and the input guide number and the set film sensitivity are set. When the aperture value corresponding to the set guide number calculated from the distance measurement value detected by the distance measuring device is smaller than the set aperture value, shooting is performed with the aperture value corresponding to the set guide number. If the flash light emitting device is operated in the guide number control diaphragm while the setting diaphragm device is opening up to the setting diaphragm value or closing after opening, if the setting aperture value is large, shooting is performed with the setting diaphragm value. And the aperture arithmetic circuit is configured to operate the flash light emitting device, Camera φ is permissible circle of confusion F, characterized in that the aperture value f at the time when the circle of confusion diameter becomes φ focal length L _e of the taking lens is set photographing distance L to satisfy the subject distance obtained by the distance measurement. 2. The diaphragm when the maximum aperture area of the diaphragm device is limited to the set diaphragm and the set brightness obtained by the set brightness calculation circuit is larger than the actual field brightness obtained by the photometric device. 2. The camera according to claim 1, wherein the aperture calculation circuit is configured so that an apparatus is held at the maximum aperture opening area.