JP2663862B2 - Camera photometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photometric device for a camera.
Is what you do. [0002] 2. Description of the Related Art Conventionally, an interchangeable lens barrel has a camera body.
A mechanical signal part is provided at the engagement part with
By providing storage means such as a ROM in the interchangeable lens barrel,
Information on the interchangeable lens barrel, for example, the open aperture value (F₀) And focus
Distance (f_mm) Etc. are transmitted to the camera body.
Had been. The camera body is composed of these interchangeable lens barrels.
Information of the maximum aperture value (F₀) And if
Gives the focal length (f_mm) In consideration of the exposure compensation amount (Z).
Was calculated. Here, the exposure compensation amount (Z) is defined as
For the brightness of the shadow or the subject field to be measured,
Measuring the light beam that has passed through the taking lens of the interchangeable lens barrel
The output of the photometric means and the image plane of the taking lens (silver-salt camera
In each case, the error of the brightness of the film surface is compensated for.
It is an amount to be corrected, and each interchangeable lens barrel is a unique value
Have. [0004] [Problems to be solved by the invention] However, in recent years,
Sharpness of directivity of the inner screen (reduced diffusion
To make it look brighter) or a lens centered on a zoom lens.
The absolute value of the exposure compensation amount (Z) increases with the diversification of camera
And the maximum aperture value (F₀) And focal length (f_mmDew against)
A remarkable decrease in the correlation of the output correction amount (Z) has occurred. You
That is, the open aperture value (F₀) And focal length (f_mm)
In the conventional method, the exposure correction amount (Z) cannot be determined.
I came. Accordingly, the present invention provides a conventional open aperture value (F
₀) As the main method of determining the exposure compensation amount (Z)
It aims to provide a new method. [0006] [Means for Solving the Problems] To solve the above problems
The lens information of the taking lens, including information on the exit pupil distance.
Input means for inputting information and light passing through the taking lens
An exposure calculating means for calculating the exposure value by measuring the light flux;
Exposure compensation from a predetermined calculation formula based on the obtained lens information
Exposure for calculating the amount and correcting the output of the exposure calculation means
Correction means, wherein the exposure correction means comprises a plurality of types of
And the reciprocal of the exit pupil distance increases.
Therefore, the output of the exposure calculation means is increased.
Select the above arithmetic expression and calculate the exposure compensation amount.
Configured. [0007] The principle of the present invention will be described with reference to FIGS.
FIGS. 4 to 7 show light beams passing through the imaging lenses 1 to 3
An image is formed on the viewfinder screen 4 and this viewfinder
The light image on the clean 4 is composed of a pentaprism 5 and an eyepiece.
6 and the light image is
The light is guided to the light receiving element 8 by the system 5 and the condenser lens 7. This
The photographing lenses 1 to 3 are located at the position of the exit pupil for convenience.
You. In addition, the pentaprism 5 includes a first reflecting surface 5a and a second reflecting surface 5a.
It is drawn and developed with the reflection surface 5b. The photographing lens 1 shown in FIG.₁
(The distance between the exit pupil and the viewfinder screen)
Mouth angle is θ₁It is. Of the light beam passing through this taking lens 1
Of which, on the finder screen 4, is separated by δ from the optical axis.
Let us focus on the luminous flux reaching the point Y. This point Y is
A light beam from the ground-side portion of the object field has arrived. Fa
Assuming that the diffusion of the inner screen 4 is extremely low
Considering that, the luminous flux passing through the point Y becomes a straight line l₁And a straight line l_Two
Will cover the sector between them. Condenser lens
The luminous flux measured by the photometric means including the photodetector 7 and the light receiving element 8 is oblique.
The hatched portion is included in the fan-shaped portion.
Therefore, an appropriate amount of light can be obtained by the photometric means. The photographing lens 2 of FIG. 5 has an exit pupil distance of FIG.
Equal to PO₁And the opening angle is θ _Two(<Θ₁5)
Is made smaller. Therefore, the luminous flux passing through the point Y
Is a straight line l_ThreeAnd a straight line l_FourAnd the range of the sector between
And completely overlaps the luminous flux range of the shaded area to be used for photometry.
No more duplication. This means that the light beam passing through point Y
Means that no means is reached. In fact,
Because the underscreen 4 has diffusivity, the point Y
Part of the light flux that has passed reaches the photometric means,
Is smaller than that of FIG. 4 because the opening angle is smaller.
You. From the above, the point Y (at the ground side of the scene)
The photometric devices (7, 8) that mainly measure the light flux
Exit pupil distance of shadow lens (PO₁) If the same, open
When the angle, that is, the open aperture value, is changed,
The force is the open aperture value (F₀) Can be ignored even if the change is corrected
There is no error, and the error is beyond the specified aperture value.
It can be seen that there is a tendency to change greatly. Next, the taking lens 1 shown in FIG.₁so
Yes, exit pupil distance PO₁It is. The center of the taking lens 1
The passing light beam reaches the point Y on the finder screen 4.
And reaches the point Y and spreads at the point Y. This diffusion distribution
Is on the ellipse in the figure, and the component T₁Used for photometry
It is. The photographing lens 3 shown in FIG.₁And the same as Fig. 6
And the exit pupil distance PO_Two(<PO₁) Shorter than in Figure 6
Made up of At this time, a point passing through the center of the taking lens 3
The luminous flux arriving at Y moves in a direction far away from the photometric means.
Because there is, it goes to the photometric means out of the diffused light at point Y
Component T_TwoIs the diffused light component T in FIG.₁Significantly smaller than
You can see that it is made up. And the difference is the finder
-The lower the diffusivity of the screen 4, the more noticeable it appears.
You. From the above, the point Y (at the ground side of the object scene)
The photometric devices (7, 8) that mainly measure the light flux
Open aperture value of the shadow lens (F₀) Is the same, exit pupil distance
(PO), the output of the light receiving element 8 produces an error.
In general, the shorter the exit pupil distance (PO), the smaller the light receiving element 8
It can be seen that the amount of received light tends to decrease. Therefore, the figure
4 and FIG. 5 and FIGS. 6 and 7
To sum up the conclusion, the photometric output is the maximum aperture value (F₀)
And the exit pupil distance (PO)
I understand. The photometric device of the present invention provides a
It is configured to reduce the effect of the pupil distance. The photometric optical system includes a viewfinder.
Measure the light beam that passed through the clean from above the eyepiece
Is shown, but the arrangement of the photometric system is limited to this.
Not the thing, for example, after the main mirror of the camera body
By placing a sub-mirror that has diffusivity on the side,
Body metering type that measures light at the bottom of the camera body
It may be something. [0014] 【Example】 -1st Example- 1 and 2 show a first embodiment, and illustrate the present invention.
Figure 2 shows the basic camera system needed. FIG.
FIG. 2 is an explanatory diagram showing an exposure correction amount, and FIG.
FIG. First, a turtle to which the present invention is applied will be described with reference to FIG.
The system will be described. Light flux that has passed through the taking lens 10
Is reflected by the main mirror 15 and
Arriving at the wheel 16. And part of this light flux is pen
Through the prism 17 to the eyepiece 18,
Another part passes through the pentaprism 17 and condenses
The light reaches the light receiving element 20. Measurement of light receiving element 20
The light output is input to the exposure calculation circuit 21 and the exposure calculation circuit 21
21 calculates the exposure value. The exposure calculation means of the present invention
In the embodiment, the condenser lens 19, the light receiving element 20, the exposure calculation circuit
21. The output of the exposure calculation circuit 21
Is input to the exposure compensation means 22, where the open aperture value is
(F₀) And the exit pupil distance (PO).
This correction method will be described later with reference to FIG. this
Full aperture (F₀) And the exit pupil distance (PO) data
Individual as mechanical signal or electrical signal of ROM data
Hold each interchangeable lens barrel and let the camera body read it.
It is common, but common. The corrected exposure value is used for exposure control.
Input to the circuit 23 to control the aperture 13 and the shutter 24
used. Next, the calculation of the exposure correction amount of the exposure correction means 22 is performed.
The output method will be described with reference to FIG. Figure 1 shows the exit pupil on the horizontal axis
Take the distance (PO) and the exposure compensation amount (Z) on the vertical axis
I have. The exposure compensation amount (Z) on the vertical axis is negative (-) on the upper side and lower on the vertical axis.
The side is positive (+). This negative (-) side is the light receiving element
If you take a picture as it is because the 20 cannot get the predetermined amount of light
Indicates that the photo is overexposed
On the positive (+) side, the photo is underexposed
It indicates that the direction will be. Sand
FIG. 7 shows that the exit pupil distance (PO) becomes shorter.
As described above, the light flux entering the film surface enters the light receiving element 8.
Component T_TwoYou can see that the (light intensity) gradually decreases
If you shoot as it is, the picture will be overexposed
I understand. On the contrary, the exit pupil distance (PO) becomes longer.
As shown in FIG. 6 and FIG.
Component T incident on the light receiving element 8₁(Light intensity)
If you shoot as it is, the photo will be unexposed
You can see that it is Therefore, in actual operation
Is the exposure correction amount from the value obtained by the exposure calculation circuit 21.
Correction is made by subtracting (Z). In calculating the exposure correction amount (Z), first,
The aperture value of the shooting lens (F₀). For example,
In the embodiment, the open aperture value (F₀) To F₀= 2.8, dark
Photographic lens (F₀> 2.8) and a bright taking lens (F
₀≤ 2.8). In addition, we classify photography lens
In the case of₀= 2.8
Needless to say, other values may be used. The photographing lenses A to F are bright photographing lenses.
(F₀≦ 2.8), and the photographing lens G (G₁, G_Two) -M
Is a dark shooting lens (F₀> 2.8) shows that these
For the lens, the exposure compensation amount is approximately determined by the following equation.
Can be The following equation is used to calculate the exposure compensation
This is an approximate expression for positive.   Dark shooting lens (F₀> 2.8) Z = 0.17 × PO-1.65 Is determined by the formula.   Bright shooting lens (F₀≤ 2.8) Z = 0.32 × PO-2.33 Is determined by the formula. Equations (1) and (2) indicate that the exit pupil distance (PO) is the first and
And the second predetermined range (this range is determined experimentally)
The exit pupil distance (PO) is small and linearity cannot be obtained.
The lower limit of the exposure compensation amount Z = -0.7 In addition, the range where the exit pupil distance (PO) is large and linearity cannot be obtained.
The upper limit of the exposure compensation amount in the box is Z = + 0.7 Is determined by the formula. The range of the exit pupil distance where this linearity cannot be obtained
Is, for example, as shown in FIGS. 6 and 7, for example, the exit pupil distance.
Release (PO₁) Going beyond a certain distance or injecting
Pupil distance (PO_Two) When it comes below a certain distance, fine
Light flux from point Y on dark screen 4 to light receiving element 8
Since the component does not change significantly, the light incident on the light receiving element 8
No significant change in volume occurs. Therefore, there is an exit pupil distance
If it becomes larger or smaller than
It can be seen that a constant correction amount (Z) is sufficient. Figure
The circles in 1 indicate the exposures of the photographing lenses A to M experimentally obtained.
Indicates the actual value of the correction amount, and two circles indicate one point
What is connected with the chain line is wide with the tele side of the zoom lens.
The value with the side. Therefore, the correction is made in parallel from the circle to the vertical axis.
The length of the dotted line below the line cannot be completely corrected after the correction.
Represents a large amount and is corrected with fairly good accuracy.
It turns out that it is. -2nd Example- FIG. 3 shows a second embodiment for explaining the present invention.
The difference from the first embodiment is that the horizontal axis represents the inverse of the exit pupil distance.
We are taking the number (1 / PO). Exit pupil distance
(PO) is generally used for correcting aberration of an autofocus device.
Is used in the form of a reciprocal, so considering data sharing
In some cases, the reciprocal is more convenient. Exit pupil of shooting lens
Distance (PO) is dispersed in the range of about 50mm to 150mm
Because there are many things and the range is about 3 times, make it the reciprocal form
Also obtains linearity. In addition, the exit pupil distance where linearity is difficult to obtain
In the range where the separation (PO) is large or small, the first implementation
As in the example, the upper and lower limits are used, and
Exposure compensation using the reciprocal of the exit pupil distance (1 / PO)
A method is possible. As in the first embodiment, the effect of the exposure correction amount (Z) is
First, the aperture value of the taking lens (F₀)so
Classify. Full aperture (F₀) To F₀= 2.8, dark
Photographic lens (F₀> 2.8) and a bright taking lens (F
₀≤ 2.8). In addition, we classify photography lens
In the case of₀= 2.8
Needless to say, other values may be used. The photographing lenses A to F are bright photographing lenses.
(F₀≦ 2.8), and the photographing lens G (G₁, G_Two) -M
Is a dark shooting lens (F₀> 2.8) shows that these
For the lens, the exposure compensation amount is approximately determined by the following equation.
Can be The following equation is used to calculate the exposure compensation
This is an approximate expression for positive.   Dark shooting lens (F₀> 2.8) Z = -165 x (1 / PO) + 1.70 Is determined by the formula.   Bright shooting lens (F₀≤ 2.8) Z = -140 x (1 / PO) + 1.89 Is determined by the formula. In the formulas and, the exit pupil distance (1 / PO) is the first and
And the second predetermined range (this range is determined experimentally)
), The exit pupil distance (1 / PO) is small, and linearity cannot be obtained.
The lower limit of the exposure compensation amount Z = + 0.7 In addition, the exit pupil distance (1 / PO) is too large to obtain linearity.
The upper limit of the exposure compensation amount in the box is Z = -0.7 Is determined by the formula. The circles in FIG. 2 indicate experimentally determined photographing lenses.
The actual values of the exposure correction amounts of the colors A to M are shown.
If the circles are connected by a dashed line,
These values are for the tele side and the wide side. Therefore, the vertical axis
The length of the dotted line drawn on the correction straight line parallel to
Represents the amount that cannot be fully corrected
It can be seen that the correction is performed with high accuracy. It should be noted that specific examples are shown in the first and second embodiments.
Actual measured values vary depending on the photometric optical system.
It is not limited to the numerical value of. Also, open aperture value
(F₀) Is classified as F₀At 2.8
In the case of limited to two series (or approximate expression)
However, for example, exposure correction can be performed using three or more approximate expressions.
May be. In this way, the more the categories, the more
However, the exposure correction amount obtained from the approximate expression
Needless to say, it is obtained as a value. Also, the first implementation
In the example, the data of the exit pupil distance (PO) is
If it is stored in the form of the reciprocal (1 / PO) of
It does not matter if you use it after calculating and using (PO)
Needless to say. [0024] As described above, according to the present invention, the exit pupil distance is obtained.
Select a calculation formula for exposure compensation according to the reciprocal of the
Since the positive amount is calculated, the exposure correction amount can be accurately calculated.
You can ask. In addition, a data table
Without having to store it in memory.
Multiple arithmetic expressions are provided to respond to
Therefore, classify the lens information in detail and calculate the exposure compensation amount.
More appropriate values can be obtained when
This is advantageous over the table method. In addition, implementation of the present invention
According to the example, the approximate expression for exposure compensation
Regarding the range that disappears, the upper limit value and the
Since the correction is made by setting a lower limit,
Exposure compensation is now possible with great precision.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing an exposure correction amount according to a first embodiment. FIG. 2 is an explanatory diagram showing a camera system. FIG. 3 is an explanatory diagram illustrating an exposure correction amount according to a second embodiment. FIG. 4 is an optical path diagram for explaining the principle of the present invention. FIG. 5 is an optical path diagram for explaining the principle of the present invention. FIG. 6 is an optical path diagram for explaining the principle of the present invention. FIG. 7 is an optical path diagram for explaining the principle of the present invention. [Description of Signs of Main Parts] 4, 16 finder screen 5, 17 pentaprism, 7, 19 condensing lens, 8, 20 light receiving element 21, exposure calculation circuit, 22 exposure correction means

Claims (1)

(57) [Claims] Input means for inputting lens information of a photographing lens including information on an exit pupil distance; exposure calculating means for measuring a light flux passing through the photographing lens to calculate an exposure value; and a predetermined value based on the input lens information. Exposure compensation means for calculating an exposure correction amount from an arithmetic expression and correcting the output of the exposure arithmetic means, wherein the exposure correction means has a plurality of types of the arithmetic expressions, and the reciprocal of the exit pupil distance is A camera according to claim 1, wherein said calculation formula is selected so as to increase the output of said exposure calculation means as the size increases, and said exposure correction amount is calculated. 2. 2. The camera according to claim 1, wherein the exposure correction unit is provided with at least one of an upper limit and a lower limit of the exposure correction amount.