JP3045808B2 - Exposure control device for single-lens reflex camera - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single-lens reflex camera with an interchangeable focus plate having a split photometric device.

[0002]

2. Description of the Related Art As a photometric device for a single-lens reflex camera, there is known a photometric device in which a photometric area in a photographing screen is divided into a plurality of sections, and a photometric value in each photometric area is evaluated to determine an exposure condition. I have. This split metering (evaluation metering)
In the apparatus, a mat focus plate having a uniform diffusion surface is used as the focus plate. In other words, the split photometric device assumes the use of a matte focus plate having a uniform diffusion surface. It is difficult to confirm whether or not this matte focus plate is in focus at the time of focusing with the naked eye (manually), but there is no problem with a recent camera having an AF function. The diffusion surface of the mat focus plate includes a surface that substantially diffuses light, such as a sanding surface, a microlens gathering surface, and a microprism surface.

However, in a high-end machine capable of exchanging a focus plate, a focus plate having a split microprism or a cross microprism in a part (generally, a center portion) is easy to focus manually (center prism focus plate). ), The following problems were found. That is, the central prism focus plate has no light diffusion property in the central prism portion. For this reason, light hardly reaches the central photometric region of the split photometric device corresponding to the central prism portion. Since the evaluation photometry by the split photometry device does not depend on the type of the focus plate, the exposure value is determined by assigning a specific weight to all photometry areas,
When the split photometry is performed using the central prism focus plate, the evaluation photometry including the photometry value of the central photometry area where light does not reach is performed, and as a result, accurate exposure cannot be obtained. In particular, since the subject brightness at the center of the screen is generally weighted at the time of evaluation photometry, a large exposure error is likely to occur. In addition, as a focus plate used for microscopy and astrophotography, a focus plate having a transparent portion provided in a part (central portion) of a focus plate entirely formed of a diffusion surface and a cross-shaped groove formed in the transparent portion is known. Are known. This focus plate also has a similar problem. In the present invention,
A focus plate having a uniform diffusion surface is referred to as a matte focus plate, and a focus plate having a non-diffusion surface in one part and a diffusion surface as a remainder is referred to as a focus plate with a non-diffusion surface.

[0004]

An object of the present invention is to provide a single-lens reflex camera having a split photometry device and a replaceable focusing plate, based on the above awareness of the problem, so that an appropriate exposure can be obtained even when a focusing plate with a non-diffusion surface is used. The aim is to obtain an exposure device that can be performed.

[0005]

SUMMARY OF THE INVENTION The present invention provides a focus plate changing mechanism that can be replaced with a mat focus plate having a uniform diffusion surface and a focus plate with a non-diffusion surface, and a focus plate with a non-diffusion surface on the focus plate. setting a plurality of divided photometric regions including the non-diffusing section metering area corresponding to the non-diffusing section, the divisional photometry device for metering a subject luminance of the divided photometric regions, respectively, this
Of each divided photometry area detected by the divided photometry device
Evaluative photometry that determines exposure factors by weighting the object brightness
Means for determining whether the mat focus plate or the focus plate with the non-diffusion part is mounted, and when the determination unit detects the mounting of the mat focus plate, Evaluative photometry using photometric values of multiple divided photometric areas including non-diffuse area photometric areas
When the exposure factor is set through the means and a focus plate with a non-diffusion portion is detected, the light measurement values of a plurality of divided photometry regions excluding the non-diffusion portion photometry region are used for the evaluation through the evaluation photometry device.
In this case, the exposure factor is set.

According to this configuration, when a focusing plate with a non-diffusion portion is attached, which does not give light to the non-diffusion portion photometry region, the photometry value of the non-diffusion portion photometry region is not used for photometry calculation, so that a large exposure error occurs. Can be prevented from occurring.

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
The single-lens reflex camera has a photographic lens 11 as shown in FIG.
Is formed on a focusing plate 14 placed on a surface equivalent to the film surface 13 via a mirror 12, and this image is observed via a pentaprism 15 and an eyepiece optical system 16. The photometric lens 17 disposed above the rear part of the pentaprism 15 uses the subject image on the focus plate 14 as a secondary light source and projects the reduced image on the evaluation photometric element 18.

The focus plate 14 is supported by a focus plate holder 20 which is rotatable about a shaft 19, and can be appropriately replaced by a known means such as a holder hook 21 or the like. FIGS. 2A, 2B, and 2C respectively show a replaceable focusing plate as a central prism focusing plate 14A, a central transmitting crosshair focusing plate 14B, and a mat focusing plate 14A.
C is schematically shown.

The central prism focus plate 14A has a prism portion 22 such as a split microprism or a cross microprism at the center thereof, and a peripheral portion other than the prism portion 22 is formed of a diffusion surface (mat surface) 23. ing. As shown in FIG. 2D, the central transmission crosshair focus plate 14B has a transmission part 24 at the center thereof.
The peripheral portion other than 4 is composed of the diffusion surface 23. A cross line 25 is engraved on the transmission part 24. The center transmission crosshair focus plate 14B is in the focused state when the eye and the crosshair 25 do not feel a shift even if the eye is slightly swung right and left on the eyepiece side of the finder. It is out of focus. Also, the prism portion 22 of the central prism focus plate 14A is a well-known prism portion in which the image is clearly seen when focused, but the image is blurred by the action of the prism when not focused. Since blurring of an image by the prism is largely caused by a slight defocus, it is suitable for focusing by the naked eye (manually). On the other hand, focusing and blurring of the image can be observed even on the diffusion surface 23, but it is not as clearly observed as the prism portion 22. Hereinafter, the central prism focus plate 14A and the central transmissive crosshair focus plate 14B will be collectively referred to as a non-diffusion surface provided focus plate 14AB. On the other hand, the mat focus plate 14C is entirely composed of the diffusion surface 23. The diffusing surface is not particularly limited as long as it substantially diffuses light, such as a sanding surface, a microlens gathering surface, and a microprism surface.

The non-diffusing surface-equipped focus plate 14AB and the matte focus plate 14C are provided on one side thereof with detachable projections 26.
The focus plate 14AB with a non-diffusion surface is further provided with a projection 27 for determination. This judging projection 27
The focus plate discriminating switch 28 (FIGS. 3A and 3B) is used when the focus plate 14AB with the non-diffusion surface is attached to the camera body.
Off). In other words, the pair of switch contact pieces 28a and 28b of the focus plate discriminating switch 28 are always in contact (ON), but when the focus plate 14AB with the non-diffusion surface is mounted at the normal position, the discrimination protrusion 27 is turned on. The contact between the switch contact pieces 28a and 28b is released and turned off. On the other hand, the mat focus plate 14 having no discrimination protrusion 27
Focus plate discrimination switch 2
8 is kept on.

FIG. 4 shows an example of setting a divided photometric area of the evaluation photometric element 18. In this evaluation photometry element 18, the photometry area of A is located at the center, and B1, B
2, C1 and C2, and further outside, D1, D2, E
There are 1 and E2 divided photometry areas. Of these, the photometric area A is the prism portion 2
2 (or the transmission section 24). The divided photometry area of the evaluation photometry element 18 is for dividing the luminance of the corresponding portion of the subject image on the focus plate 14AB with a non-diffusion surface or the matte focus plate 14C and performing photometry. With respect to the formed subject image, it can be accurately measured. However, prism part 2
Since the light 2 or the transmission portion 24 refracts light in a certain direction, the light does not reach the corresponding central photometry area A. FIG. 5 shows this state. A point light source is scanned in the horizontal direction from L to R at the center of one surface of a focusing plate 14AB with a non-diffusion surface, and the transmitted light amount is measured on the other surface. At the portion 22 or the transmission portion 24, the amount of received light sharply decreases.

The present invention is intended to eliminate disadvantages caused by this phenomenon, and FIG. 6 shows a control block diagram thereof. The exposure control means 30 includes a photometric element selection (exclusion) means 31, an evaluation photometry calculation means 32, and an exposure factor setting (decision) means 33. The photometric element selection (exclusion) means 31 outputs the outputs from the nine divided photometric areas A to E2,
A signal from a focus plate discrimination switch (focus plate discrimination means) 28 is given. The photometric element selection (exclusion) means 31
When the focusing plate 14AB with the non-diffusion surface is mounted, the output of the divided photometric area A is excluded and the evaluation / photometric operation is performed by the evaluation / measurement operation unit 32, and the exposure factor setting (decision) unit 33 is set to the road factor (shutter). Speed, aperture value, etc.). When the mat focus plate 14C is mounted, the exposure factor is similarly determined using the outputs of all the divided photometric areas A to E2.

FIG. 7 shows a flowchart of the above control. In step S11, the focus plate discrimination switch 2
8 is ON or not, that is, the focus plate 14AB with the non-diffusion surface
Is determined, and if the focus plate 14AB with the non-diffusion surface is mounted, the photometric calculation B is performed using photometric values in all photometric regions except the central photometric region A. (Steps S12 and S13). On the other hand, in step S11, the focus plate 14AB with the non-diffusion surface
Is not attached, that is, the mat focus plate 14C
Is detected, the photometric calculation A is performed using photometric values in all photometric areas including the central photometric area A (S14, S15). Therefore, in any case, the exposure factor can be accurately determined and a correct exposure can be obtained.

In the above embodiment, the focus plate 14 with the non-diffusion portion is used.
Although the present invention has been described by taking as an example the case where a non-diffusion portion exists at the center of AB, the present invention also applies to the case where a focus plate having a non-diffusion portion other than the center is selectively used. Applicable.

[0015]

As described above, according to the present invention, even if a focus plate having a non-diffusing portion is used in a part of a single-lens reflex camera with a focus plate having a split photometric device, the entire surface is formed of a matte surface. Even with a focus plate, correct exposure can be obtained.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a general configuration of a single-lens reflex camera provided with a focus plate changing mechanism and a split photometric device.

FIG. 2A is a schematic perspective view of a central prism focus plate.

FIG. 2B is a schematic perspective view of a center cross hair focus plate;

FIG. 2C is a schematic perspective view of a mat focus plate.

FIG. 2D is a cross-sectional view of the center of the center transmission crosshair focus plate.

FIG. 3A is a front view showing a state of a focus plate discriminating switch when the focus plate of FIG. 2A or 2B is mounted.

FIG. 3B is a front view showing a state of a focus plate discrimination switch when the focus plate of FIG. 2C is mounted.

FIG. 4 is a plan view showing an example of an evaluation photometry element of the split photometry device.

FIG. 5 is a graph showing an intensity distribution of transmitted light when light is applied to a central prism focus plate.

FIG. 6 is a block diagram of an exposure control device according to the present invention.

FIG. 7 is a flowchart illustrating a control example of the exposure control device according to the present invention.

[Description of Signs] 11 Photographing lens 12 Mirror 13 Film surface 14A Central prism focus plate (focus plate 14AB with non-diffusion portion) 14B Central transmission crosshair focus plate (focus plate 14AB with non-diffusion portion) 14C Mat focus plate 17 Photometric lens 18 Evaluation photometric element 19 Axis 20 Focus plate holder 22 Prism 23 Diffusion surface 24 Transmissive part 25 Crosshair 26 Detachable protrusion 27 Discrimination protrusion 28 Focus plate discrimination switch (means) 30 Exposure control means 31 Photometry element selection (exclusion) ) Means 32 Evaluative photometric calculation means 33 Exposure factor setting (decision) means A Central photometric area (non-diffuse area photometric area)

Claims (1)

(57) [Claims] A focus plate exchange mechanism which can be exchanged between a matte focus plate having a uniform diffusion surface and a focus plate with a non-diffusion portion having a non-diffusion portion in a part; a plurality of sets of divided photometric regions, divided into a photometric device for metering a subject luminance of the divided light metering areas respectively including the non-diffusing section metering area corresponding to the non-diffusing portion of the focusing plate attached; the divisional photometry device Of each divided photometry area detected by
Evaluation measurement that determines the exposure factor by weighting the subject brightness
Light means; discriminating means for discriminating which of the matte focus plate and focus plate with non-diffusion portion is mounted; when the discrimination means detects the mounting of the matte focus plate, the non-diffusion portion photometric area is Using the photometric value of the plurality of divided photometric areas including the exposure factor is set via the evaluation photometric means, when the focus plate with non-diffusion portion is detected,
An exposure calculating device for setting an exposure factor via the above-mentioned evaluative metering means by using photometric values of a plurality of divided photometric regions excluding the non-diffused portion photometric region; and an exposure device for a single-lens reflex camera. Control device.