JPH0455485B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Field of Application) The present invention relates to a strobe light emission control device that accurately controls the light emission timing of a strobe light with a small memory capacity in a variable focus camera in which the aperture value changes. (Prior Art) A variable focus camera generally changes the focal length f of the photographic lens by moving the lens or by inserting and removing an auxiliary lens as the main lens moves. On the other hand, as is known in the art, in a lens in which the position of the exit pupil coincides with the principal point, if the diameter of the exit pupil is D, then the relationship is D/f=1/F, where F is the open aperture value.
This shows that in general, in a variable focus camera with a built-in aperture, the short focal length lens Lf (W) and the long focal length lens f (T) have different F numbers even if they have the same aperture diameter. . In other words, even if exposure is performed under the same shutter conditions, the amount of exposure on the film surface will be different between f(W) and f(T). Figure 4 illustrates this, and shows the same shutter conditions (exposure time) using an electromagnetic drive program shutter.
This shows that the amount of exposure on the film surface is different because the F number is different when performing exposure. In conventional variable-focus cameras, it has been proposed to compensate for changes in the aperture value due to changes in the focal length of the photographic lens by switching the aperture in front of the AE receiver and changing the filter density. It's here. This made the structure of the camera complicated. In addition, in the case of a variable focus camera that stores the shutter speed relative to the subject brightness and performs AE exposure based on this, individual tables for f(W), f(T), or other focal lengths are stored in the memory. However, it is also possible to perform AE exposure by calling up the table according to the focal length.In a camera that uses a shutter that also functions as an aperture, exposure amount control during strobe photography can be performed using the aperture diameter change curve shown in Figure 4. This can be done by making various changes in the shutter opening process shown in A, and this is known per se. Even in the case of controlling the exposure amount during flash photography by controlling the light emission start time, it is conceivable to take the same means as described above when applying it to a variable focus camera. However, in a variable focus camera, it is necessary to prepare a table of strobe light emission start times for each focal length, which requires a huge amount of memory capacity. (Object and structure of the invention) The present invention has been made in view of the above points,
The purpose of this technology is to accurately control the light emission timing value from the shutter open signal output to the strobe light emission start signal output in a variable focus camera without requiring a complicated mechanism or a huge memory capacity. In order to achieve this, a table is provided in which the light emission timing values from the shutter open signal output to the strobe light emission start signal output are determined in accordance with the film sensitivity value and the shooting distance, and changes are made on the table as the focal length is switched. The light emission timing value is shifted in the direction in which the film sensitivity changes based on the difference in the open aperture value. (Example) The present invention will be described below based on the drawings. Figure 1 shows two examples of a variable focus camera.
This shows a focus camera. Figure 1A shows the lens barrel 1 pushed toward the camera to create a short focus f(W), and Figure 1B shows the lens barrel 1 pulled out from the camera to create a long focal point. The state of f(T) is shown, and 2 shows the film surface. Main lens system 3 is used as a photographic lens.
The main lens system 3 is attached to the lens barrel 1, and when the lens barrel 1 is pushed into the guide member 5 of the camera body, the auxiliary lens system 4 is detachable. is retracted out of the optical path to form a short focus lens f(W), and when the lens barrel 1 is pulled out from the guide member 5, the auxiliary lens system 4 is on the optical path and is combined with the main lens system 3 to form a short focus lens f(W). Focal lens f(T)
form. Further, a shutter device 6 which also serves as an aperture is provided within the main lens system 3. The lens barrel 1 moves back and forth on the optical axis along the guide member 5. The guide member 5 is provided with micro switches S(W) and S(T), and the micro switch S(W) is at the short focus lens f(W) position, and the micro switch is at the long focus lens f(T) position. Each switch S(T) is turned on. The maximum aperture value of the lens is F: 3.3 for the short focal length lens f(W) and F: 5.8 for the long focal length lens system f(T), and when expressed in EV value, there is a difference of 1.2/3 EV. FIG. 2 shows a block diagram of a variable focus camera to which the strobe light emission control device according to the present invention is applied, in which 10 is a film sensitivity reading circuit for reading ISO sensitivity information from a film magazine of a DX type film, and 11 is a film sensitivity reading circuit from the camera. A distance measuring unit that outputs information according to the distance to the subject, 12 a focal length information switch corresponding to the micro switches S(W) and S(T) shown in Figure 1B, and 13 outputs subject brightness information. A photometric unit consisting of CdS etc., 14
calculates the shutter seconds from the shutter open command to the shutter close command and the light emission timing value from the shutter open command to the strobe light release command based on the above ISO sensitivity information, subject distance information, focal length information, and subject brightness information. A microcomputer-configured controller that outputs a shutter close signal and a strobe light emission signal; 15, a table memory that stores the relationship between ISO sensitivity and light emission timing as a table; 16;
is a strobe light emitting circuit, 17 is an electromagnetic shutter 1
This is a shutter driver for driving 8. The distance from the lens to the subject measured by the distance measuring unit 11 is determined by multiple AF points (for example, 13).
Divided into zones. So table memory 15
A table showing the relationship between each A zone and the light emission timing value (in milliseconds) for each ISO sensitivity index as shown in Table 1 is stored in advance. This first table shows the light emission timing values for the f(W) lens, and the EFISO zone in the left column is 1/3EV.
(EV is the exposure value).

[Table] The light emission timing values shown in this table are the values created by the controller 14. That is, as one example, the controller 14 measures time from the time when the shutter open signal is issued, and issues a strobe light emission command at the timing shown in this table. As another example, a sensor such as a switch may be provided to detect the start of the opening operation of the shutter blade, and timing may be started from the signal of this sensor, and a strobe light emission command may be issued at the timing shown in the table above. . Now, the ISO sensitivity index of the film used is automatically read by the film sensitivity reading circuit 10.
The distance to the subject is measured by the distance measuring unit 11,
From the focal length information switch 12 to the short focus lens f(W)
When the focal length information of the long focus lens f(T) is output, the controller 14 reads out the corresponding light emission timing value from the light emission timing table stored in the table memory 15. For example, using a short focus lens f(W) and a film with ISO sensitivity 400,
For subjects at a distance of AF zone 5
Select the light emission timing value of 15.6ms and send the strobe light emission signal to the strobe light emission circuit 1 at that timing.
6 to fire the strobe. However, when the photographic lens is switched to the long focus lens f(T) for the same subject, the focal length information switch 12 outputs a signal to that effect. For short focal length lenses f(W), the maximum aperture value of the lens is F:
3.3. For the long focal length lens f(T), since F: 5.8 makes the lens darker by 1 2/3 EV in EV value, the controller 14 changes the ISO sensitivity index in the light emission timing table in Table 1 to the EFISO zone. Shift it 5 steps lower. In the above example,
Flash timing value corresponding to ISO sensitivity index 125
Reads 22.6ms and sends a strobe light signal at this timing. In this way, when switching the photographic lens between the short focus lens f(W) and the long focus f(T), the flash timing value is shifted in the direction that changes the ISO sensitivity by the difference in the open aperture value. You can get the correct exposure just by Although the above example describes a camera that can switch between two types of focal lengths, even if the camera has a switchable focal length of more than 2 types, the ISO sensitivity index versus strobe firing timing will change depending on the change in the open aperture value. By shifting the sensitivity table of value correspondences, it is possible to perform appropriate exposure regardless of changes in the focal length of the photographic lens. FIG. 3 shows a flowchart of strobe light emission control for a bifocal camera according to the present invention. The process starts with the first-stage release switch which is turned on by operating the first-stage release button, and first the ISO sensitivity of the loaded film is read by the film sensitivity reading circuit 10 (see FIG. 2) (F-1). Subsequently, photometry by the photometry unit 13 (F-2) and distance measurement by the distance measurement unit 11 (F-3) are performed. For light metering, release 2 by pressing the release button in two steps.
This continues until the stage switch is turned on (F-4,
F-5). When the two-stage release switch is turned on, the lens is electrically driven (F-6), and the electromagnetic shutter is once energized in the closing direction (F-7), and is accurately returned to its initial position. Thereafter, after waiting for a period of time for stabilization (F-8), it is determined whether or not it is the strobe photography mode based on the status of the strobe switch (F-9). As a result, if it is not in flash photography mode, open the shutter (F-10),
Wait for the time TAE determined by the photometric data (F-11) and close the shutter (F-12). After waiting for a short time (F-13), the film is wound (F-14). However, when it is determined that the flash photography mode is selected in step (F-9), the short focal length lens f
It is determined from the information from the focal length information switch 12 (see FIG. 2) whether the long focal length lens f(T) for which (W) is selected is selected (F-15). As a result, if it is a short focus lens f(W), the controller 14 continues to set the corresponding light emission timing value from the light emission timing table stored in the table memory 15 based on the film ISO sensitivity and the AF zone based on the distance measurement value. Extrude (F-17). Conversely, if the long focus lens f(T) is selected, the controller 15 selects the short focus lens f(W) and the long focus lens f.
EFISO zone 5 determined by the difference in open aperture from (T)
The light emission timing value is shifted by steps in the direction in which the film sensitivity decreases (F-16), and the corresponding light emission timing value TAF is read out. Thereafter, the shutter is opened (F-18), and after waiting for the above-mentioned light emission timing value TAF (F-19), a light emission signal is sent to the strobe light emitting circuit 16 to cause the strobe to emit light (F-20). After the strobe light is emitted, the steps (F-12, F-13, F-14) described above are followed. Furthermore, in the above embodiment, the aperture values of f(W) and f(T) differ by 1.2/3EV, and the table is set in steps of 1/3EV. It is appropriate to set the sensitivity zone and the photometry zone in steps. (Effects of the Invention) As explained above, the present invention provides a variable focus camera in which the maximum aperture value changes, in which a table is stored in advance that defines the relationship between distance measurement values and strobe light emission timing values for each film sensitivity. In addition, when the focal length is changed, the light emission timing value is determined by shifting the light emission timing value in the direction in which the film sensitivity changes according to the difference in the open aperture value, so that By simply storing the light emission timing table, appropriate light emission timing values for other focal lengths can be obtained, and appropriate exposure can be achieved with a small memory capacity.

[Brief explanation of the drawing]

Figures 1A and 2B are diagrams showing the short focus and long focus lens positions in a bifocal camera, Figure 2 is a block diagram of a bifocal camera to which the strobe light emission control device of the present invention is applied, and Figure 3 is a diagram showing the lens positions of the short focus and long focus lenses in a bifocal camera. FIG. 4, which is a flowchart of strobe light emission control according to the invention, is a diagram showing the difference in exposure amount in a bifocal camera. 10...Film sensitivity reading circuit, 11...Distance measuring unit, 12...Focus information switch, 13...
Photometry unit, 14... Controller, 15...
Table memory, 16...Strobe light emitting circuit, 1
7... Shutter driver, 18... Electromagnetic drive shutter.

Claims (1)

[Claims] 1. In a strobe light emission control device for a camera that has a built-in shutter that also functions as an aperture and has a focal length switching lens unit that changes the maximum aperture value by changing the focal length of the photographic lens, the shutter is opened in accordance with the film sensitivity value and the shooting distance. A table is provided that defines the light emission timing value from the signal output to the strobe light emission start signal output, and the light emission timing is set on the table in a direction that changes the film sensitivity based on the difference in the maximum aperture value that changes as the focal length is changed. A strobe light emission control device for a camera, characterized in that the value is shifted.