JPH01230028A - Exposure controller for variable focusing camera - Google Patents

Abstract

PURPOSE:To control the shutter second of long seconds by separately obtaining shutter closing time in case of obtaining appropriate exposure after the full opening of the shutter according to effective exposing time and shutter full opening time. CONSTITUTION:The title controller is provided with a 1st table 6 which stores corresponding relation between an exposure value and shutter blade opening time in case of obtaining the appropriate exposure before the full opening of the shutter blade and a 2nd table 7 which stores the corresponding relation between them in case of obtaining the appropriate exposure after the full opening of the shutter blade. When it is judged that the appropriate exposure is obtained before the full opening thereof, the closing time determination circuit 8 for the shutter blade determines a shutter blade closing time according to the time obtained from the 1st table 6 based on the exposure value already corrected. When it is judged that the appropriate exposure is obtained after the full opening, the closing time determination circuit 8 determines the closing time of a sector according to a time obtained by adding half time obtained from the 1st table 6 based on the full opening exposure value to the time obtained from the 2nd table 7 based on the corrected exposure value. Thus, the exposure can be easily controlled even in case of low luminance where the appropriate exposure is obtained after the full opening of the shutter blade.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is applicable to exposure control of a lens-shutter type variable focus camera that can change the focal length and, in particular, changes the aperture diameter when fully opened according to the change in the focal length. Regarding equipment.

[Prior art]

As a conventional example of such a device, Japanese Patent Application Laid-Open No. 61-1620
There is an exposure control device for a variable focus camera described in Japanese Patent No. 32.

This camera has a correspondence table between the photometric value at a predetermined focal length and the shutter speed, and when the focal length changes, the photometric value is shifted according to the focal length to correspond to the change in aperture diameter. , the shirt data time is read from this table.

[Problem to be solved by the invention]

However, in this conventional example, the shutter speed can only be determined in a region where the aperture value changes according to the aperture of the shutter blade. In other words, it was not possible to achieve a long exposure in which the proper exposure was achieved after the shutter blades were fully opened. If long-time exposure is to be achieved, mechanical γ conversion is required, which has the drawback of complicating the mechanical system.

This invention was made to deal with the above-mentioned circumstances,
To provide an exposure control device that can control the shutter speed at long exposures using an extremely simple method in a variable focus camera that has a shutter blade that also serves as an aperture and changes the aperture diameter when fully opened according to changes in focal length. That purpose.

[Means for Solving the Problems] An exposure control device for a variable focus camera according to the present invention has the following features:
As shown in the figure, there is a first table 6 that stores the correspondence between the exposure value at a predetermined focal length and the shutter blade opening time when the proper exposure is achieved before the shutter blade is fully opened, and the proper exposure after the shutter blade is fully opened. It has a second table 7 that stores the correspondence between the exposure value and the effective exposure time at a predetermined focal length when .

An exposure value (EV value) determined based on the photometric value of the subject and film sensitivity, and focal length information f of the variable focus lens are supplied to the correction circuit 3. The correction circuit 3 includes a first table 6,
In order to make the second table 7 usable by shifting the table according to the difference between the created focal length and the actual focal length, the exposure values are corrected for the first table 6 and the second table 7, respectively. .

The focal length information f is supplied to the full-open exposure value calculation circuit 4, and an exposure value at which the shutter blades are fully open (full-open exposure value) is determined according to the focal length. The full-open exposure value and the exposure value corrected for the first table 6 are compared by the comparison circuit 5, and it is determined whether the proper exposure is before or after the shutter blade is fully opened.

That is, if the corrected exposure value is equal to or greater than the full-open exposure value, it is determined that proper exposure is achieved before the shutter blade is fully opened. If the corrected exposure value is less than the full-open exposure value, it is determined that proper exposure is achieved after the shutter blade is fully opened.

If it is determined that proper exposure will be achieved before the shutter blade is fully opened, the shutter blade closing timing determination circuit 8 determines the shutter blade closing timing from the time obtained from the first table 6 based on the corrected exposure value.

If it is determined that proper exposure will be achieved after full opening, the closing timing determining circuit 8 uses the second table 7 based on the corrected exposure value.
The first table 6 is based on the full exposure value at the time obtained from
The sector closing time is determined by the time obtained by adding half of the time obtained from .

[Effect]

According to this invention, by determining the shutter closing timing using the effective exposure time, exposure can be easily controlled even in the case of low brightness where proper exposure is achieved after the shutter blades are fully opened.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an exposure control device for a variable focus camera according to the present invention will be described below with reference to the drawings.

The variable focus camera of this embodiment has a shutter blade that also serves as an aperture, and when the focal length changes, the aperture diameter when fully opened changes accordingly. FIG. 2 shows this using the aperture waveform of the shutter blade.

From FIG. 2, it can be seen that the time from when the shutter blades start opening until they reach full opening changes depending on the change in focal length.

Here, in the region where the aperture value changes according to the aperture of the shutter blade (the so-called ° triangular aperture region), the exposure value (E
V value) and the shutter blade opening time (T) have a fixed relationship once the focal length is determined. - As an example, Table 1 shows a correspondence table (first table) between the exposure value and the shutter blade opening time at the wide end (shortest focal length). Here, the shutter blade opening time T at the wide end
o(W) is approximately 20m5, and the open aperture value Fo(ν
) is 4.46. Since Table 1 may be used with a shift as described later, it also includes a shutter blade opening time T longer than 20 m5.

Table 1 This table 1 is the first table 6 in FIG.

In this way, Table 1 is a correspondence table between the exposure value at the wide end and the shutter blade opening time, but if the focal length at the time of shooting changes from the wide end, the exposure value changes linearly accordingly. By correcting the exposure value and shifting the table, the shutter blade opening time at any focal length can be read from Table 1.

The difference between the exposure value at an arbitrary focal length f and the exposure value at the wide end W at an arbitrary time T in the triangular aperture area shown in FIG. 3, the correction amount ΔE V (f), is constant as follows. be. That is, the exposure value also changes linearly with changes in focal length.

ΔEv(f)-Ev(W,T)-EV(f,T)-l0
g21(Fo(W)2TO(W))/(Fo(f')
2To(f'))l-(1) Here, the meaning of each parameter is as follows.

EV (ν, T): Exposure value at the wide end at an arbitrary time T Ev (f', T): Exposure value at an arbitrary focal length f at an arbitrary time T F o (W): Open aperture value at the wide end F o(
('): Open aperture value To(f') at an arbitrary focal length f: Time taken until the shutter blades are fully open at the wide end To(f): Time taken until the shutter blades are fully opened at an arbitrary focal length f Sometimes the correction amount may be calculated using equation (1) each time the focal length changes, but since the change in focal length is finite,
Each focal length f and the correction amount ΔE V are calculated in advance based on equation (1).
Find the relationship (r) and make a table. This is shown in Table 2. Table 2 is stored in the correction circuit 3 of FIG.

Table 2 By referring to the first table shown in Table 1, using the corrected exposure value EV' shown in equation (2) as the EV value, the appropriate value for any focal length f in the triangular aperture area can be determined It is possible to determine the shutter blade opening time for exposure, that is, the shutter blade closing timing.

Ev゛-EV-ΔEV(r) +++ (
2) Next, as shown in FIG. 4, the case where proper exposure is achieved after the shutter blade is fully opened (T1) will be explained.

First, in equation (1), the difference (correction amount) ΔEV(f')' between the exposure value at the wide end and the exposure value at an arbitrary focal length f at any effective exposure time T° rather than at any time T is It will look like this:

ΔEV (f')'-EV (W, T')-EV
(f', T')-10g2 (F o(W)/F
o(f)) 2... (3) Here, too, the correction amount ΔEV(f)' is calculated in advance from equation (3) for each focal length f and is tabulated. This is shown in Table 3. This Table 3 is also stored in the correction circuit 3 of FIG.

Table 3 In other words, as in the case of the triangular aperture area, once the exposure value EV determined from the photometric value and ISO sensitivity and the correction amount ΔEV (f)' at each focal length in equation (3) are determined, based on the following equation By correcting the exposure value and referring to the table shown in Table 4 using the corrected exposure value EV'', the effective exposure time T° at any focal length can be determined.

Table 4 is the second table 7 in FIG.

EV''-EV-4EV (f)' (4) Table 4 Here, as shown in Fig. 4, T1 is the time until the shutter blade reaches full open, and T2 is the time from when the shutter blade is fully opened until the shutter blade closes. Then, the time T1+72 from the start of opening to the closing of the shutter blade can be expressed as follows using the effective exposure time T°.

T1+T2-T1+ (T'-0,5xT1)-T'
10o, 5xT1 ・= (5) At each focal length, whether the proper exposure is before or after the shutter blades are fully opened is determined by the full-open exposure value E at which the shutter blades are fully opened.
This can be determined by comparing Vz(f') with the corrected exposure value EV' for drawing the first table. EV'≧
If EVz(r), it can be determined that proper exposure occurs before the shirt is fully opened, and if EV'<EVz(f), it can be determined that proper exposure occurs after the shirt is fully opened. The full-open exposure value EVz(f) is uniquely determined at each focal length, and here, this is also determined in advance at each focal length, and
Make it a table. This is Table 5. Table 5 is stored in the full-open exposure value calculation circuit 4 shown in FIG.

Table 5 A flowchart of the exposure calculation subroutine according to this embodiment based on the above explanation is shown in FIG.

First, in step 10, set the film sensitivity (ISO)
Read information Sv. In step 20, focal length information f is read. In step 30, the photometric value BV is read.

In step 4o, an exposure value EV-BV+SV is determined from the photometric value BV and the film sensitivity information Sv.

In step 50, the correction amount ΔE V at the focal length f
(f') is read from Table 2. In step 6o, the corrected exposure value EV' −EV−ΔEV for drawing the first table
(f') is determined from equation (2). In step 70, the full-open exposure value EVz(f) at which the shutter blades are fully opened at the focal length f is read out from Table 5.

In step 80, the full-open exposure value EV,z(f') is compared with the corrected exposure value EV', and it is determined whether proper exposure is achieved before or after the shutter blade is fully opened. Here, EV'
If ≧EVz(f'), the correct exposure will be before the shutter blade is fully opened, and if EV'<EVZ(f'), the correct exposure will be after the shutter blade is fully opened. judge.

When it is determined that the proper exposure occurs before the shutter blade is fully opened, in step 90 the shutter blade opening time T is read out from Table 1 using the corrected exposure value EV' as the EV value, and in step 95 the shutter closing timing Ts is read out. Let it be mT.

When it is determined that proper exposure is achieved after the shutter blades are fully opened, the correction amount ΔEV(f')' at the focal length f is read from Table 3 in step 100. In step 110, the corrected exposure value EV"-EV- is used to draw the second table.
AEV[f)' is found from equation (4). Step 120
Then, the effective exposure time is read out from Table 4 using the corrected exposure value EV'' as the EV value. In step 130, the full-open exposure value EVz(
The time T read from Table 1 with f) as the EV value is the fully open time T1 of the shutter blade. In step 140, T'+
Let 0.5XT1 be the shutter blade closing timing Ts.

Thereby, whether the proper exposure is achieved before or after the shutter blade is fully opened, the timing of closing the shutter blade can be determined for the product.

Note that this invention is not limited to the embodiments described above, and can be modified in various ways. For example, there is no need to store Tables 1 to 5 as they are; instead, only the formulas showing the correspondence relationships are stored, and instead of reading data at an address that corresponds to the input data, the input data is based on this formula. You may also calculate and output the data.

Moreover, each numerical value is for explanation, and is not limited to these in any way.

〔Effect of the invention〕

As explained above, according to the present invention, in a variable focus camera that changes the aperture diameter when fully opened according to changes in focal length, the shutter closing time when a proper exposure is achieved after the shutter is fully opened is the effective exposure time and the shutter is fully opened. By determining the exposure time and the time separately, an exposure control device is provided which can control the shutter speed at a long time using a simple method.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an outline of the exposure control device for a variable focus camera according to the present invention, Fig. 2 is a diagram showing changes in the aperture waveform of the shutter blade depending on the focal length, and Fig. 3 is a diagram showing changes in the aperture waveform of the shutter blade depending on the focal length. A diagram showing the difference between the exposure value and the exposure value at a given focal length, Figure 4 is a diagram explaining the shutter blade closing timing when the proper exposure is after the shutter blade is fully opened, and Figure 5 1 is a flowchart showing the operation of an embodiment of an exposure control device for a variable focus camera according to the present invention. 3... Correction circuit, 4... Fully open exposure value calculation circuit, 5.
... Comparison circuit, 6... First table, 7... Second table, 8... Closing timing determining circuit. Applicant's agent Patent attorney Atsushi Tsuboi 2L Procedural amendment 1. Indication of the case Japanese Patent Application No. 63-55011 2 Name of the invention Exposure control device for variable focus camera 3 Person who makes correction Relationship to the case Patent applicant (037) Olympus Optical Industry Co., Ltd. 4 Agent Chiyoda, Tokyo 3-7-2-7, Kasumigaseki-ku, Contents of the amendment (1) The scope of the claims will be corrected as shown in the attached sheet. (2) "At the wide end...4.46" stated on page 6, line 18 to page 6, line 20 of the specification.
``The time To(v) until the shutter blades are fully open at the wide end is approximately 20 m51The open aperture value Fo(
w) is 4.46. ” he corrected. (3) r To( described in page 11, line 16 of the specification)
1') Correct J to rTo(ν). (4) Figure 1 of the drawing will be corrected as shown in the attached sheet. 2. Scope of the Claims In an exposure control device for a variable focus camera that has a shutter blade that also serves as an aperture and whose aperture diameter changes when fully opened according to changes in focal length, there is a predetermined value for achieving proper exposure before the shutter blade is fully opened. A first table means for storing a correspondence between an exposure value at a focal length and a shutter blade opening time, and a correspondence between an exposure value at a predetermined focal length and an effective exposure time when proper exposure is achieved after the shutter blade is fully opened. a second table means for storing the relationship; a means for correcting the exposure value for each of the first and second table means according to the focal length at the time of photographing;
A means for determining a full-open exposure value at which the shutter blade is fully opened according to the focal length at the time of photographing, and a means for determining the correct exposure by comparing the exposure value corrected for the first table means with the full-open exposure value. means for determining whether the shutter blades are fully opened before or after the shutter blades are fully opened, and if it is determined that the appropriate exposure will be obtained before the shutter blades are fully opened, based on the time determined from the first table means using the corrected exposure value. If it is determined that the appropriate exposure will be obtained after the shutter blades are fully opened, the second
Exposure control for a variable focus camera characterized by comprising means for determining shutter blade closing timing based on the time obtained from the table and the time obtained from the first table means using the fully open exposure value. ,Device. Applicant's agent Patent attorney Atsushi Tsuboi

Claims (1)

[Claims] In an exposure control device for a variable focus camera that has a shutter blade that also serves as an aperture and changes the diameter of the aperture when it is fully open according to changes in the focal length, the exposure value at a predetermined focal length when the appropriate exposure is achieved before the shutter blade is fully opened. and a second table means for storing a correspondence relationship between an exposure value at a predetermined focal length and an effective exposure time when proper exposure is achieved after the shutter blade is fully opened.
table means, means for correcting the exposure value for each of the first and second table means according to the focal length at the time of photographing, and means for determining a full-open exposure value at which the shutter blade is fully opened according to the focal length at the time of photographing. a means for comparing the exposure value corrected for the first table means with the full-open exposure value and determining whether the appropriate exposure is before or after the shutter blade is fully opened; If it is determined that the correct exposure will be obtained before, the corrected exposure value is used to set the first exposure value.
The shutter blade closing timing is determined based on the time calculated from the table means, and if it is determined that the appropriate exposure will be obtained after the shutter blade is fully opened, the time calculated from the second table is determined using the corrected exposure value. , means for determining shutter blade closing timing based on the time determined from the first table means using the fully open exposure value.