JP2817153B2 - TTL automatic light control camera - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a camera that controls the amount of light emitted from an electronic flash device by a TTL automatic light control method. More specifically, the dimming level is adjusted according to the type of the electronic flash device used.

B. Prior Art FIG. 4 shows the configuration of a camera equipped with a TTL automatic light control device. A camera lens 1 and an external electronic flash device 3 are mounted on a camera body 1. FIG. 4 shows a case where the camera is in a photographing state, in which the main mirror 4 is mirrored up, and a light beam emitted from the electronic flash device 3 and reflected from the subject passes through the photographing lens 2 and is reflected by the film surface 5. The light enters the light receiving element 7 via the condenser lens 6. The light beam received by the light receiving element 7 is converted into an electric signal and time-integrated. When the integrated amount reaches a predetermined TLL dimming level predetermined by a dimming circuit (not shown), the dimming circuit And the flashing device 3 stops emitting light. Reference numeral 8 denotes a pentaprism, 9 denotes an aperture, and 10 denotes a shutter.

C. Problems to be Solved by the Invention In such a conventional TTL automatic light control type camera, the light emission waveform or the light emission stop performance (determined by the time from when the light emission stop signal is obtained until the light emission actually stops) The dimming level described above is constant, although a plurality of electronic flash devices having different performances can be used. For this reason, there has been a problem that the amount of light with respect to a subject having the same luminance varies depending on the electronic flash device used, or even if an appropriate exposure is obtained in the electronic flash device, the exposure is under or over in a certain electronic flash device. In addition,
In the present specification, the light emission waveform or the light emission stopping performance is called a light emission characteristic.

 This will be described in detail with reference to FIGS.

FIG. 5 illustrates that the amount of flash light varies depending on the time difference from when the flash stop signal is sent to the electronic flash device to when the flash tube actually stops emitting light. The time t is plotted on the axis.

Here, t ₀ is the flash start time, t ₁ is the time for sending a flash stop signal, t ₂ and t ₃ is the time when the actual light emission of the flash tube is stopped. Since the flash light quantity is an integral value, when different times and from time and time t ₁ from time t ₁ to time t ₂ to time t _3, only the flash light quantity amounts shown in the shaded differently.

FIG. 6 is a diagram for explaining that the flash light amount differs due to the difference in the flash waveform.

In the flash waveforms A and B, even if the time from the transmission of the flash stop signal at the time t ₁ ′ to the time t ₂ ′ at which the light emission actually stops is the same, the flash light amount differs by the hatched portion.

Actually, a difference in the total amount of flash light shown in FIGS. 5 and 6 occurs.

Further, in so-called daytime synchro photography, the amount of flash light is reduced to take a picture with a natural feeling, and the above-mentioned problem is further increased. For example, the fifth
In FIG. 7, which is the same flash waveform as in the figure, the time t ₁ ″ at which the flash stop signal is sent is made earlier than the time t ₂ in FIG. Here, t ₂ ″ −t ₁ ″ = t ₂ −t ₁ , t ₃ ″ −t ₁ ″ = t
₃ When -t _1, t ₃ "because the integral value between -t _2, t ₃ -t ₂ is the difference in the flash light quantity, FIG. 7 daytime sync shooting to stop flashing when the light intensity larger 5, the difference in the flash light amount becomes larger, that is, the area of the oblique lines becomes larger than that in the case of FIG.

A technical problem of the present invention is to irradiate the same amount of light to a subject having the same luminance when shooting with various electronic flash devices having different light emission characteristics.

D. Means for Solving the Problem (1) The present invention will be described with reference to FIG. 1 which is a diagram corresponding to the claims.
It has a dimming means 103 that receives reflected light from a subject incident through 02 and outputs a light emission stop command to the flash tube 101 when the amount of received light reaches a predetermined reference value, and outputs a light emission stop command. The present invention is applied to a TTL automatic light control camera that can use a plurality of predetermined electronic flash devices, which have different time integral values of the light intensity from when the light emission actually stops.

The technical problem described above is solved by the following configuration.

That is, the identification means 104 for identifying which of the plurality of electronic flash devices is used, and a reference when the identification means 104 identifies the use of the electronic flash device having a large time integration value. The use of an electronic flash device having a small value and a small time integration value is identified by the identification means 104.
And a reference value changing means 105 for increasing the reference value when identifying the electronic flash device so that the time integration value becomes substantially constant under the same imaging condition regardless of which electronic flash device is used.

(2) The time integral value of claim 1 is determined by determining the length of time from when a light emission stop command is output to when light emission actually stops and / or
Alternatively, it changes based on the magnitude of the light intensity with the passage of time from the start of light emission.

E. Operation The electronic flash device to be used is identified by the identification means 104.
The reference value changing means 105 changes a reference value determined according to the identified electronic flash device. That is, in the case of an electronic flash device in which the time integration value increases, the reference value is reduced, and in the case of an electronic flash device in which the time integration value decreases, the reference value is increased. As a result, the time integration value becomes substantially constant under the same photographing conditions, regardless of which electronic flash device is used.

F. Embodiment An embodiment will be described based on FIG. 2 and FIG.

FIG. 2 is a block diagram of a control system of the TTL automatic light control device camera.

The photometric light receiving element 22 outputs a signal corresponding to the brightness of the subject and inputs the signal to the photometric circuit 23. The photometric circuit 23 calculates the luminance based on the input signal and inputs the calculated luminance to the CPU 21. The ISO sensitivity reading circuit 27 reads the film sensitivity from the film cartridge and inputs it to the CPU 21. CPU21 is a photometric circuit
The exposure value is calculated based on the luminance information from 23 and the film sensitivity from the ISO sensitivity reading circuit 27 to calculate the shutter speed and the control aperture value. Then, the CPU 21 controls the drive of the S shutter and the aperture through the shutter control circuit 24 and the aperture control circuit 25 so that the shutter speed and the aperture value calculated by the CPU 21 become the same.

Further, the CPU 21 calculates a dimming level according to the film sensitivity, the subject brightness, or the type of the electronic flash device, and sets the dimming level in the level setting unit 41. In normal flash photography at low brightness, the dimming level is changed depending on the film sensitivity and the electronic flash device used, and in daytime synchro photography, the dimming level is changed depending on the subject brightness and the electronic flash device used.

Further, in FIG. 2, reference numeral 26 denotes a leading-curtain running completion detecting circuit which detects completion of running of the leading-curtain shutter and inputs a leading-curtain running completion signal to the CPU 21. In response to this detection, the CPU 21
A light emission start signal is sent to an integrator 42 and a light emitting circuit 31 described later.
Reference numeral 28 denotes an accessory shoe, which is connected to the CPU 21 via a signal line 29. When a non-communication type electronic flash device or a communication type electronic flash device described later is mounted, the accessory shoe
An electronic flash device mounting signal is output to the CPU 21 via 28.

The light control circuit (light control means) 40 outputs a light emission stop command signal to the CPU 21 when the integrated value of the signal from the TTL automatic light control light receiving element 7 reaches the light control level. For this purpose, the dimming circuit 40 includes a level setter 41 for setting the dimming level based on a signal from the CPU 21, an integrator 42 for integrating a signal from the light receiving element 7 for TTL automatic dimming, and a setter.
It comprises a comparator 43 that compares the dimming level from 41 with the integrated value from the integrator 42 and outputs a light emission stop command signal when the integrated value reaches the dimming level. The integrator 42 starts its operation with a light emission start signal output from the CPU 21 when the front curtain travel is completed.

The electronic flash device 30 is built in the camera body, and the light emitting circuit 31
And a flash tube 32. When a light emission start signal is input from the CPU 21 to the light emission circuit 31, the flash tube 32 starts light emission,
When the light emission stop signal is input from the flash unit 32, the light emission of the flash tube 32 is stopped.

In this embodiment, an electronic flash device built in the camera body is used.
In addition to 30, two types of external electronic flash devices mounted on the accessory shoe 28 can be used. One of the external electronic flash devices has a CPU therein so that communication with the camera body is possible. The other of the external electronic flash devices is a conventionally well-known electronic flash device in which light emission is controlled by receiving a light emission start signal and a light emission stop signal from a camera body. Here, the former is called a communication type electronic flash device, and the latter is called a non-communication type electronic flash device. The three electronic flash devices can be identified as follows. When the electronic flash device mounting signal is not input to the CPU 21 from the accessory shoe 28, the built-in electronic flash device is used. When only the electronic flash device mounting signal is input, the non-communication type electronic flash device, the electronic flash device mounting signal and the communication signal are used. Is input, it can be identified as a communication type electronic flash device. Therefore, the CPU 21 forms an identification unit.

The operation procedure of the device configured as described above will be described with reference to the flowchart of FIG.

When the program shown in FIG. 3 is executed in conjunction with the release operation, the CPU 21 first performs photometric processing in step S1, and reads luminance information from the photometric circuit 23. In step S2, it is determined whether or not flash photography is to be performed based on the luminance information. If the subject has a brightness equal to or lower than the predetermined brightness, or the subject is backlit, it is determined that flash photography has been performed, and the process proceeds to step S3. If it is determined that the flash photography is not performed, the process proceeds to step S20, in which a normal photography process without using the electronic flash device is performed.

In step S3, it is determined whether or not to perform daytime synchro shooting. If it is determined that the daytime synchro shooting is performed, the process proceeds to step S8. If it is determined that the daytime synchro shooting is not performed, that is, if it is determined that the flash photography is normal, the process proceeds to step S4.

In step S4, the electronic flash device to be used is identified. If it is determined in step S4 that the device is a built-in electronic flash device, the dimming level R is set to R1 in step S5, and step S4
If the electronic flash device is determined to be non-communication type in step S6, the dimming level R is set to R2 in step S6, and if the electronic flash device is determined to be communication type in step S4, the dimming level R is set to R3 in step S7. I do. Here, R1 <R2 <R3, and R1, R2, R3
The value of, even when using electronic flash devices with different emission characteristics,
It is set so that subjects with the same brightness are irradiated with the same amount of light and photographed with the same amount of exposure. Note that the values of R1, R2, and R3 also vary depending on the film sensitivity.

On the other hand, if it is determined in step S3 that daylight synchro shooting has been performed, in step S8, a reference dimming level RR according to the subject luminance is set. Next, in step S9, the electronic flash device to be used is identified as described above. Step S9
In step S10, the correction amount ΔR1 given to the built-in electronic flash device is subtracted from the reference dimming level RR, and the result is set as the dimming level R in step S10.
If it is determined in step S9 that the electronic flash device is a non-communication type electronic flash device, in step S11, the correction amount ΔR
2 is subtracted, and it is set as the dimming level R. Step S
If it is determined in step 9 that the electronic flash device is a communication type electronic flash device, the correction amount ΔR3 is subtracted from the reference dimming level RR in step S12, and this is set as the dimming level R. Note that these correction amounts ΔR1 to ΔR3
Are in a relationship of ΔR1>ΔR2> ΔR3.

When the dimming level R is set in this way, the step
In S13, it is determined whether or not a full-press operation has been performed based on a signal from a full-press switch (not shown). If a negative determination is made, it is determined in step S19 whether or not a half-press operation has been performed. Is determined by the signal from Step S19
If affirmative, the process returns to step S1, and if negative, the process proceeds to the end.

If it is determined in step S13 that the shutter is fully pressed, the running of the shutter front curtain is started in step S14, and it is determined in step S15 whether or not the flashing of the shutter front curtain is completed based on the presence or absence of the front curtain running completion signal. If the result is negative, the process waits until the result in step S15 is affirmed, and if the result is affirmative, the process proceeds to step S16 to output a light emission start signal to, for example, the electronic flash device 30 and the integrator 41 built in the camera body. The light emission circuit 31 causes the flash tube 32 to emit light by the light emission start signal, and the integrator 42 starts the integration operation. When the integrated value of the integrator 42 reaches the dimming level R set as described above, a light emission stop command signal is input from the comparator 43 to the CPU 21. The CPU 21 waits for the input of the light emission stop command signal in step S17. When the input is determined, the CPU 21 sends a light emission stop signal to the light emitting circuit 31 in step S18, whereby the light emission of the flash tube 32 is stopped.

As described above, in the present embodiment, the electronic flash device to be used is identified and the dimming level is adjusted in accordance with the light emission characteristics of each electronic flash device when performing desired photographing by properly using the three types of electronic flash devices. Therefore, the same amount of light is applied to the subject having the same brightness no matter which electronic flash device is used for photographing, and an optimum exposure amount can be obtained.

The present invention is characterized in that the dimming level is set according to the electronic flash device to be used. Therefore, the type of the electronic flash device to be used is not limited to the above embodiment. Also,
The identification of the electronic flash device is not limited to the above-described embodiment, and the operator may manually input an identification signal according to the electronic flash device used.

In the above embodiment, the dimming level is the reference value and the CPU 2
1 and the level setting device 41 constitute reference value changing means, and the CPU 21 constitutes identification means.

G. Effects of the Invention According to the present invention, the reference value as the dimming level is set according to the electronic flash device to be used.
When performing flash photography using the automatic light control method, proper exposure can be obtained even if various electronic flash devices having different light emission characteristics are used.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims. FIG. 2 and FIG. 3 illustrate one embodiment.
FIG. 3 is a block diagram showing a configuration of a control system of the TTL automatic light control camera, and FIG. 3 is a flowchart showing an example of a procedure for adjusting a light control level. FIG. 4 is a diagram for explaining a camera equipped with an electronic flash device of the TTL automatic light control system, and FIGS. 5 to 7 are diagrams showing various flash waveforms. 3: External electronic flash device 7: TTL automatic light control light receiving element 21: CPU, 26: Light emission start circuit 28: Accessory shoe 30: Built-in electronic flash device 31: Light emitting circuit, 32, 101: Flash tube 40: TTL automatic light control Circuit 41: Level setting unit, 42: Integrator 43: Comparator, 102: Photographing lens 103: Dimming means, 104: Identification means 105: Reference value changing means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03B 7/16 G03B 15/05

Claims (2)

(57) [Claims] 1. A light control means for receiving reflected light from a subject incident through a photographing lens after a flash tube emits light, and outputting a light emission stop command to the flash tube when the amount of received light reaches a predetermined reference value. It is used in a TTL automatic light control camera capable of using a plurality of predetermined electronic flash devices, having different time integral values of the light intensity from outputting the light emission stop command to actually stopping the light emission. Identification means for identifying which one of the plurality of electronic flash devices the electronic flash device is, and the reference value when the identification means identifies the use of the electronic flash device such that the time integration value is increased. When the identification means identifies the use of an electronic flash device such that the time integration value is reduced, the reference value is increased, and any electronic flash device can be used under the same photographing conditions. TTL, characterized by comprising a reference-value change means the time integral value is in roughly a constant
Automatic light control camera. 2. The camera according to claim 1, wherein the time integration value is a length of time from when the light emission stop command is output to when light emission is actually stopped and / or a light associated with a lapse of time from the start of light emission. A TTL automatic light control camera that changes based on the intensity.