JPS5917541A - Compensation system of correction amount of aperture of camera - Google Patents

Abstract

PURPOSE:To make curvature corrections adapted to a photometric distribution determined by an output difference between circuits which measure light at the center part (main subject) and circumference (subordinate subject) of a picture plane respectively, by determining the correction amount (curvature compensation amount) of an aperture according to the output difference. CONSTITUTION:The output Va of a main subject light metering circuit LM1 for measuring light in the center of the picture plane and the outputs V1-Vm of background light metering circuits LN1-LNm for measuring light at the circumference are inputted to an arithmetic circuit WCT, which outputs compensation information weighted properly on the basis of the brightness difference between a main and a subordinate subject. The difference between this output and the output Va is calculated DEF and transmitted to an aperture compensation information generating circuit COM to make corrections so that the aperture compensation information of a mounted lens is adapted to the photometric distribution based upon the output difference. The outputs of the circuits WCT and COM and the output of a photographic information setting circuit IFS are processed OP1 to perform high-precision exposure control.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a camera aperture correction amount correction method that allows the aperture correction amount to be adjusted based on the luminance difference between a main subject and a sub-subject.

In general, if the brightness of the subject is not uniform, for example, the center part is brighter than the peripheral part, or vice versa, if the brightness difference between the parts is small, then Even if the subject is metered on average, there will not be a significant amount of metering error. However, if the brightness of each part of the object is extremely different, the average photometry method has the disadvantage that accurate photometry cannot be expected. For example, if the peripheral part of the subject has much higher brightness than the central part, the light receiving element for photometry will be affected by the brightness of the peripheral light flux, and will measure the brightness of only the peripheral part, not the central part. I end up metering. In this case, the photometric value simply indicates the brightness around the subject, and when setting the camera's exposure conditions based on this brightness value, for example,
Although an appropriate exposure value is given to the periphery of the subject, inappropriate exposure cannot be given to the central part. In many cases, the area to be photometered is located in the center of the photometric field of view, and therefore, such a photometry method cannot provide accurate photometry and is not suitable as a general-purpose photometry method. There wasn't.

In order to solve these drawbacks, a method has been proposed in which multiple light-receiving elements are placed on the image forming surface of a conventional photometry condensing lens, and the outputs of the light-receiving elements are weighted in various ways to improve photometry accuracy. has been done.

Although efforts have been made to improve the photometry accuracy for luminance in this way, an effective method for correcting the aperture correction amount of the photometry circuit based on changes in the photometry distribution due to weighting has not yet been demonstrated. .

The present invention has been developed in view of the above-mentioned circumstances, and detects the difference between the output of a first photometering circuit that measures the light of the main subject and the output of the second photometer that measures the light of the secondary subject, A correction method for the aperture correction amount of a camera, in which the aperture correction amount of the photographic lens is determined by a correction circuit, and the output of the first and second photometry circuits is corrected using the output of the correction circuit to control the exposure amount. This is what we are trying to provide.

An embodiment of the present invention will be described below with reference to the drawings.

Figure 1 shows a single-lens reflex camera, where LN is the photographing lens, QM is the quick return mirror, PG is the focusing plate, CL is the condenser lens, and PR.

is a pentaprism, BM is a beam splitter, EL is an eyepiece lens, ML is a photometric focusing lens, SP is a photometric unit, MT is an exposure display device such as an ammeter, ST is a shutter, and FM is a film.

Figure 2 shows the photometry section SP in Figure 1.
The size of P corresponds to the size of the screen, ri, M.

PN1 is a light receiving element that measures the light of the main subject at the center of the screen, and PN1 is a light receiving element that measures the light of the secondary subject at the periphery of the screen. The measured light outputs of the first and second light receiving elements corresponding to the F number of the photographic lens are as shown in FIG.

The aperture correction amount AI/c of the photometric output characteristic AM of the first photodetector PM is smaller than the aperture correction amount A v c 1 of the photometric output fi AN of the second photodetector PN.

These aperture correction amounts Avc, , Avc are correction amounts required during aperture photometry. In a camera that controls the exposure amount by correcting and adding the output of PN to the output of PM, the aperture correction amount is Av according to the amount of correction addition from PN.
c.

FIG. 4 shows a control circuit that attempts to obtain highly accurate exposure by changing from A v c @ to A v c @.

In Fig. 4, there are m photometric circuits for the sub-object, but it may be one as shown in Fig. 2, or a fifth
It may be four as shown in the figure. In the figure, LM.

is a photometry circuit for main subject photometry consisting of a light-receiving element PM, an operational amplifier OM, a logarithmic compression element DM, a level adjustment resistor VM, and LN, ~LNm are light-receiving elements PN, ~P
Nm, operational amplifier ON tori ~ ON m, logarithmic compression element D
N.

~DN+n, and level adjustment resistors VN1 to VNm. This is a photometry circuit for background photometry. WCT is a calculation resistance R,
−Rm, R,, ~R,=, operational amplifier OA-,, OA
, This arithmetic circuit WCT performs a weighting correction calculation by adding the outputs of the photometric circuit In and the photometric circuits LN, .about.LNm. DEF is the resistance R,l~
R11, clamp diode D1, DI, operational amplifier O
A signal corresponding to the output of the arithmetic circuit WCT is generated in the differential circuit DEF.

CO, M are resistances u, R+41% operational amplifier OP
,, An aperture correction information generation circuit consisting of a variable resistor VR having a brush BR that slides in conjunction with the F number pin AP of the photographic lens, this aperture correction information generation circuit COM applies aperture correction to the output of the differential circuit DEF. Correct the information.

Or) C is a photographing information setting circuit IFS, arithmetic resistor R,...
-R+, . . . This is a circuit for exposure calculation, display, and control consisting of an operational amplifier OP, a meter MT, a control circuit CKT, and a time control electromagnet M g +.

Next, the operation of the above configuration will be explained.

Metering circuit LM for main subject metering that measures the center of the screen
, and outputs M to Vm of photometry circuits LN, -LNm for photometry of a sub-subject (background) that measures the peripheral part of the screen are applied to an arithmetic circuit WCT. The output VOA of the operational amplifier OA of this operational circuit WCT is therefore the operational amplifier O
The output VOA of A, and the output of the operational amplifier OA adjacent thereto, are appropriately weighted based on the difference between the main subject and the background, producing corrected luminance information. Then, the difference between the output VOA of the operational amplifier OA and the output Va of the photometric circuit LMl is taken by the differential circuit 1)EF to produce an operational amplifier OB.

The output Vop, is increased by the voltage V due to the diodes D, ,D
A.

It shows how it is clamped at VB. This clamp circuit is for protecting the input of aperture correction information when the luminance difference between the main subject and the background is extremely large.

The output of the operational amplifier OP is the aperture correction information generation circuit COM.
The aperture correction information of the attached lens is corrected. In other words, the aperture correction amount can be multiplied by a certain amount in conjunction with the value of the output Vop of the operational amplifier OP, and the output Vop of the operational amplifier OP. On the other hand, it is possible to perform aperture correction at a constant rate.

Figure 7 shows the state of this aperture correction. A is when the output of the background is very large compared to the output of the upper subject, and B is when the background and main subject appear in almost the same way. , C are cases where the output of the main subject is much larger than the output of the background.

The figure shows an example where aperture correction is performed only for lenses with a diameter larger than F2, 8! l), in the case of a lens with a diameter smaller than F2.8, the bottle AP is short and the slider BR is
, is removed from the variable resistor VR, the switch SW is turned off, a constant bias voltage 'Vc is applied to the output of the operational amplifier OP, and information on lens aperture correction is deleted. The output of the operational amplifier OA, the aperture correction information of the operational amplifier OP, and the output of the photographing information setting circuit IFS are outputted to the operational amplifier OF.

The calculation result is displayed on the meter MT. On the other hand, the calculation result is transmitted to the control circuit CKT, and the magnet M
The shutter is controlled by gl.

As described above, when the present invention is used, the aperture correction amount is corrected according to the luminance distribution between the main subject and the secondary subject such as the background, so that the exposure is always appropriate regardless of the luminance distribution of the subject. It has a remarkable effect of controlling the amount.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of a single-lens reflex camera showing an embodiment of the present invention, Fig. 2 is a diagram showing an example of the photometry section shown in Fig. 1, and Fig. 3 is a photometry output characteristic of the light receiving element shown in Fig. 2. Figure 4 is the first
FIG. 5 is a diagram showing another example of the photometry section shown in FIG. 1, and FIG. 6 is a diagram showing the operational amplifier O shown in FIG. 4.
FIG. 7 is an aperture correction amount characteristic diagram of the aperture correction information generation circuit shown in FIG. 4. PM: Light receiving element that measures the main subject at the center of the screen. PN, -PNm... Light-receiving element that measures the light of a sub-subject at the periphery of the screen. LM,...photometering circuit LN, -LNm for main subject photometry
...Photometric circuit for background photometry WCT...Arithmetic circuit DEF...Differential circuit COM...Aperture correction information generation circuit ODC...Circuit for exposure calculation, display, and control Applicant: Canon Corporation 0

Claims (1)

[Claims] The difference between the output of the first photometering circuit that meters the main subject and the output of the second photometering circuit that meters the sub-subject is detected, and the correction circuit determines the aperture correction amount of the photographing lens according to this output difference. A method for correcting an aperture correction amount of a camera, characterized in that the output of the first and second photometric circuits is corrected using the output of the correction circuit to control the exposure amount.