JPH01239537A - Stroboscopic light emission controller for variable focusing camera - Google Patents

Abstract

PURPOSE:To lower a cost without increasing the capacity of a memory by using a table which is used for controlling exposure and the correction circuit of an exposure value so that the flashmatic control of a stroboscope can be performed. CONSTITUTION:The exposure value EV corresponding to a shutter blade closing time at the time of controlling exposure equal to a stroboscopic light emitting time in a specified focal distance is computed by a computation circuit 3 based on object distance information (d) and film sensitivity information ISO. The exposure value EV is corrected according to focal distance information (f) by a correction circuit 5. By using the corrected value EV, the shutter blade closing time is read out from the table 6 in which the relation of a shutter closing timing to the exposure value in case of natural light is regulated and a stroboscopic light emission signal is generated with an appropriate stop value by a stroboscopic light emitting time determination circuit 7 based on the time read out. Now, the correction circuit 5 and the table 6 are also used as the circuit for controlling the exposure in case of natural light. Thus, the cost can be lowered without increasing the storage capacity.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is applicable to strobe light emission 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 a control device.

[Prior art]

Generally, in many variable focus cameras, when the focal length changes, the F value also changes. If you install a Flashmatic strobe on such a camera and try to make the strobe fire at a predetermined F value by controlling the strobe's firing timing, if the focal length differs, the firing timing will change. There must be. That is, if the focal length changes, the F number will change even if the aperture diameter is the same, so even if the subject is under the same conditions, it is necessary to change the aperture diameter, that is, the light emission timing, depending on the focal length.

Then, by storing the relationship between subject distance, film sensitivity, and strobe firing timing as a table, and shifting the film sensitivity according to changes in focal length, the strobe firing timing for all focal lengths is determined using one table. A strobe light emission control device for a camera that can do this is described in Japanese Patent Laid-Open No. 61-269130.

[Problem to be solved by the invention]

However, in this conventional example, it is necessary to provide a table for determining the strobe firing timing separately from a table showing the correspondence between the EV value for exposure control and the shutter blade opening timing, and it is necessary to increase the storage capacity of the ROM. However, there was a drawback that the cost was high. Another drawback is that it does not take into account the case where the strobe guide number changes as the focal length changes.

This invention was made to deal with the above-mentioned circumstances,
The object of the present invention is to provide a strobe light emission control device that can perform flashmatic control in an extremely simple manner 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. .

[Means and operations for solving the problems] In the strobe light emission control device for a variable focus camera according to the present invention, as shown in FIG. An exposure value E V (PM) corresponding to the shutter blade opening timing during exposure @IJ, which is equal to the strobe light emission timing at the focal length, is calculated.

This exposure value E V (FM) is corrected (shifted) by the correction circuit 5 according to the focal length information f. Using the corrected exposure value E V (PM), the shutter blade opening timing is read out from the table 6 that defines the relationship between the exposure value and the shutter opening timing in the case of natural light, and the strobe light emission timing determining circuit 7 reads this out. A strobe light emission signal is generated at an appropriate aperture value based on time.

Here, the correction circuit 5 and table 6 are also used as a circuit for exposure control in the case of natural light. That is, the exposure value information EV determined from the subject brightness and film sensitivity is corrected by the correction circuit 5 according to the focal length information f. Based on the time read out from the table 6 based on this corrected EV value, the shutter opening timing determining circuit 9 determines the shutter blade opening timing for proper exposure.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a strobe light emission control device for a variable focus camera according to the present invention will be described below with reference to the drawings. This invention is characterized in that the strobe light emission timing is determined by also using a table showing the correspondence between the EV value for exposure control and the shutter blade closing timing in the case of natural light. Exposure control will be explained, and then the determination of strobe light emission timing using the table will be explained.

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 to when they reach full opening changes as the focal length changes.

Here, in a region where the aperture value changes according to the aperture of the shutter blade (so-called triangular aperture region), the exposure value (EV
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 #I). Here, the shutter blade opening time To at the wide end
(W) is approximately 20 m5, and the open aperture value F o (W
) 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 included in 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.

Any focal length 1liI at any time T in the triangular aperture region shown in FIG. The difference between the exposure value of f and the exposure value of wide end W, the correction amount ΔE V <r), is constant as follows. That is, the exposure value also changes linearly with changes in focal length.

AEv(f')-EV(W,T)-EV(f,T)-
Iogz l(F o(W)” T o(W))/(
Fo(f)2To(f'))l - (1) where,
The meaning of each parameter is as follows.

EV (shi, T): Exposure value at the wide end at an arbitrary time T EV (1', T): Exposure value at an arbitrary focal length f at an arbitrary time T Fo (ν): Open aperture value F at the wide end o(r)
: Open aperture value To(f) at an arbitrary focal length f: Time until the shutter blades are fully open at the wide end To(1'): Time until the shutter blades are fully open at an arbitrary focal pressure #f Focus at the time of shooting The correction amount may be calculated using equation (1) each time the distance 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 5 of FIG.

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

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

First, in equation (1), the difference (correction amount) ΔEV(')' between the exposure value at the wide end and the exposure value at any focal length f at any effective exposure time T', not at any time T, is as follows: become that way.

ΔEV (1')'-EV (V, T')-EV
(1', T')-l0g2(F o(W)/F o
(D) 2... (3) Here again, 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 5 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, it is possible to determine the effective exposure time T° at any focal length. It is included in Table 6 in Figure 1.

Ev=-Ev-ΔEv (f) ゛ -= (4)
Table 4 Here, as shown in Figure 4, if the time until the shutter blades reach full open is T1, and the time from when the shutter blades are fully opened to the time when the shutter blades are opened is T2, then the time from the start of the shutter blade opening until the shutter blades are opened is T1+T2, which is the effective exposure. Using time T', it can be expressed as follows.

T1+T2T1+ (T'-0,5xT1)-T'
+0,5XT1... (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 EVz((') at which the shutter blades are fully opened. This can be determined by comparing the corrected exposure value EV' for drawing the first table.EV'
If ≧EVz(f), it can be determined that proper exposure is achieved before the shirt is fully opened, and if EV'<EVz(f), it can be determined that proper exposure is achieved after the shirt is fully opened. The full-open exposure value EVz(f) is uniquely determined at each focal length,
Here, if this is also determined in advance for each focal length, it will be as shown in Table 5.

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 S■. In step 20, focal length information f is read. In step 30, the photometric value BV is read.

At step 40, 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 60, the corrected exposure value EV'-EV-ΔEV for drawing the first table
(f') is determined from equation (2). In step 70, a full-open exposure value E at which the shutter blades at the focal length f are fully open
Read Vz(f) from Table 5.

In step 80, the full-open exposure value EVz(r) and the corrected exposure value EV' are compared, and it is determined whether the proper exposure is before or after the shutter blade is fully opened. Here, EV' ≧
If EVz(r), the proper exposure is before the shutter blade is fully opened, and if EV'<EVz(r),
It is determined that proper exposure is achieved after the shutter blade is fully opened.

If it is determined that proper exposure is achieved 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 opening time Ts - Let it be T.

When it is determined that proper exposure is achieved after the shutter blade is fully opened, the correction amount ΔEV(r)' at the focal length f is read from Table 3 in step 100. In step 110,
Corrected exposure value EV”-EV-4 for drawing the second table
EV([')' 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 opening timing Ts.

This makes it possible to easily determine the timing to open the shutter blades, regardless of whether the appropriate exposure occurs before or after the shutter blades are fully opened.

Next, control of strobe light emission timing will be explained. In flashmatic control, it is sufficient to find the aperture value according to the subject distance, guide number, and film sensitivity, but here, the aperture value will be replaced with the shutter blade opening time. This allows the table (Table 1) to be used.

First, as shown in FIG. 2, when the inclination of the aperture is a in any focus processing f, the aperture time T is expressed as follows.

T-1/(axF2)-(6) Generally, the equation for calculating the exposure value in apex calculation is expressed as follows.

EV −1og2 (2xF2/T) −(7)
By substituting equation (6) into equation (7), the following equation is obtained.

EV-logz (2xaxF') - (8)
Generally, the aperture value during flashmatic is expressed as follows.

F - (GNo(f')/d)(g)] side "...
(9) Here, d is the subject distance, S is the film sensitivity, and GNo(f') is the strobe guide number.

The strobe guide number changes as the focal length changes.

Therefore, by substituting equation (9) into equation (8), the aperture value during flashmatic can be pseudo-replaced with the exposure value. The pseudo exposure value at this time is expressed as follows.

E V (PM) = logz (2X a x
(G No(1')/d)4X (S/100)2
1...(10) Here, logz G
No(1')-G V .

If 1og25-SV% logz d=DV,
Equation (10) is expressed as follows.

E'/(PM) = l0g2(2Xa) +4xGV
+2x (SV-5) -4xDV -(LL) Furthermore, as shown in FIG. 6, at any subject distance d, the EV value at the shortest focal length W and any focal length f
The difference in EV value of the shortest focal length corresponding to the aperture time T' is as follows.

A E V (PM) - E V (W, T) - E V
(W, T')-2X logz (F o(v)
2x To(v)/F o(1')2X To(v)/F o(1')
')) - (12) Equation (12) can be expressed from equation (1) as follows.

ΔE V (PM) - 2XΔE V (1')
... (13) In equation (11), if the slope of the aperture is rewritten as the slope at the shortest focus pressure #IW, E V (PM) - l0g2 (2/ F o (w)2
x T o(v)) 14xGV+2x(SV-5)
4xDV - (14) Here, if the shift amount of the EV value at an arbitrary focal length f is taken into account, the equation (14) can be transformed as follows.

EV(PM)=logz(2/Fo(v)2XTo
(w))+4xGV+2x(SV-5) -4xDV+2xΔE V (r) -(15) Therefore, since the first term in equation (15) is a constant, GV, SV, DV
, ΔEV(r) are determined, the strobe light emission timing at which exposure is appropriate during strobe light emission can be referred to from Table 1. Here, DV is determined as follows.

Table 6 A method for deriving strobe light emission timing will be described with reference to the flowchart shown in FIG.

First, in step 210, film sensitivity (ISO) information S
Read V. In step 220, E V (FM)-23
The focal length information f is read at 0. In step 240 G V
−Calculate log 2 G No(f). In step 250, add EV [FM) + 4XGV to new EV (PM)
shall be. In step 260, E V (PM) + 2
ΔE V (f) is newly set to E V (PM). In step 270, object distance information d is obtained. Step 2
At 80, read DV from Table 6. At step 290, EV (
PM)-4xDV is newly set as EV (PM).

As a result, E V (PM) of equation (15) is obtained.

In step 300, the full-open exposure value EVz(r) is read from Table 5 using this E V (PM).

In step 310, the full-open exposure value EVz(r) and the exposure value E are determined.
Compare V()'M). Here, E V (PM
)≧EVz(r), step 330 is executed immediately, and if EV(PM)<EVz(r), the full open exposure value EVz(r) is changed to the exposure value E in step 320.
After setting V (PM), step 330 is executed. In step 330, the shutter blade opening time T is read from Table 1 using the exposure value E V (PM), and this is set as the strobe light emission timing. As a result, the strobe light emission timing can be determined using Table 1, and a table dedicated to strobe control is not required.

Note that this invention is not limited to the embodiments described above, and can be modified in various ways, and each numerical value in the table is for explanation and is not limited to these in any way.

〔Effect of the invention〕

As explained above, according to the present invention, a table used for exposure control and an EV
Since flashmatic control of the strobe can be performed using the rfL correction circuit, a low-cost strobe light emission control device can be provided without increasing the memory capacity.

[Brief explanation of the drawing]

Fig. 1 is a diagram schematically showing a strobe light emission 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 the change in the aperture waveform of the shutter blade depending on the focal length. Figure 4 is a diagram showing the difference between the exposure value at a given focal length and the exposure value at a given focal length. Figure 4 is a diagram explaining the timing of opening the shutter blade when the proper exposure is achieved after the shutter blade is fully opened. Figure 5 is a flowchart showing an example of exposure control in natural light according to the present invention, FIG. 6 is a diagram showing an aperture waveform for explaining strobe light emission control according to the present invention, and FIG. 7 is a strobe light emission control device for a variable focus camera according to the present invention. 3 is a flowchart showing the operation of one embodiment of the present invention. 3... Arithmetic circuit, 5... Correction circuit, 6... Table, 7... Strobe light emission timing determining circuit, 8... Shutter opening timing determining circuit. Applicant's representative Patent attorney Atsushi Tsuboi To(w) To(f) tJF, 3 Figure 4 To Figure 6 Figure 1, Display of case Patent application No. 63-65905 2, Title of invention Strobe light emission of variable focus camera Control device 3, relationship with the amended person case Patent applicant (037) Olympus Optical Industry Co., Ltd. 4, agent 3-7-2 Kasumigaseki, Chiyoda-ku, Tokyo (1) Amended the scope of patent claims as shown in the attached sheet do. (2) From page 6, line 7 to page 6, line 9 of the specification, "The shutter blade at the wide end is 4.46" written in J2. The time To(ν) until it fully opens is approximately 20 m5.The open aperture value F at that time
Let o(w) be 4.46. ” he corrected. (3) r T o stated on page 11, line 5 of the specification
(f) Correct J as r T o (vN). (4) From page 25, line 14 of the specification to page 27, line 1
Table 6 written up to the second line is corrected as shown in the attached sheet. 2. Scope of Claims In a strobe light emission 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, the brightness of a subject at a predetermined focal length and the shutter blade aperture a table means for storing a correspondence relationship with time; and a table means for obtaining a shutter opening time for obtaining an aperture value during flashmatic corresponding to a subject distance and film sensitivity at a predetermined focal length from the table means; means for determining a parameter corresponding to the brightness of the subject in the table means from the sensitivity; means for correcting the parameter according to the focal length at the time of photographing; and time determined from the table means using the corrected parameter. A strobe light emission control device for a variable focus camera, comprising means for determining strobe light emission timing based on. Applicant's agent Patent attorney Atsushi Tsuboi

Claims (1)

[Claims] In a strobe light emission control device for a variable-focus camera that has a shutter blade that also serves as an aperture and changes the aperture diameter when fully open according to changes in focal length, the correspondence between the brightness of the subject at a predetermined focal length and the shutter blade opening time is determined. A table means for storing information, and a shutter opening time for obtaining an aperture value during flashmatic corresponding to a subject distance and film sensitivity at a predetermined focal length from the table means. means for determining parameters corresponding to the brightness of the subject; means for correcting the parameters according to the focal length at the time of photographing; and strobe light emission timing based on the time determined from the table means using the corrected parameters. A strobe light emission control device for a variable focus camera, comprising means for determining.