JPH0433383B2 - - Google Patents

Description

[Detailed description of the invention]

FIELD OF INDUSTRIAL APPLICATION The present invention relates to a light meter. 2. Description of the Related Art Conventionally, an exposure meter is known that calculates and displays data corresponding to an aperture value from a photometric value and preset film sensitivity and exposure time (shutter speed). Problems to be Solved by the Invention However, the above-described exposure meter has a problem when measuring light at two points under constant light to determine the difference in brightness (so-called contrast). This means that when the film sensitivity and exposure time are constant, the aperture value (F number) is 1.4, 2, 2.8, 4, 5.6, 8, 11,
The first reason is that the contrast is difficult to understand intuitively because it changes like 16, 22, etc. Furthermore, if the exposure time setting changes, the aperture value display will change even though the metering value remains the same.
The second reason is that photometry must be performed at both points while keeping the set value of the exposure time fixed. Therefore, we installed two display sections on a single light meter,
One display section displays the exposure value EV, which is suitable for measuring contrast because it has a linear relationship with the photometric value and does not depend on the exposure time setting value, and the other display section displays it according to the exposure time setting value. A device configured to display an aperture value (F number) that changes in value is known. However, such a configuration requires two display units, making the configuration large and difficult to make compact.In addition, since the exposure value and F-number are displayed at the same time, it is possible to read the displayed value by mistake. There is also the risk of failure when using it for shooting. Purpose of the Invention In view of the above, the present invention provides a simple and compact exposure meter that makes it easy to measure and understand contrast, and furthermore, when taking pictures using a flash, the aperture value can be adjusted. The purpose of this invention is to provide a light meter that displays corresponding data. Configuration for Solving the Problems In order to achieve the above object, the present invention is characterized by: a photometric means that outputs a photometric signal according to a photometric value; and a film sensitivity signal that corresponds to a set film sensitivity. a film sensitivity setting means for outputting an exposure time signal corresponding to the set exposure time; and an exposure time setting means for outputting an exposure time signal corresponding to the set exposure time; A calculation means for calculating data or data corresponding to the exposure value, and a display mode switch for switching between an aperture value display mode that displays data corresponding to the above aperture value and an exposure value display mode that displays data corresponding to the above exposure value. means for switching between a flash light mode for measuring flash light and a constant light mode for measuring steady light; and when the aperture value display mode is selected by the display mode switching means, the above operation Data corresponding to the aperture value calculated by the means is displayed, and when the exposure value display mode is selected, data corresponding to the exposure value calculated by the calculation means is displayed. a display means having a single display section for selectively switching display contents; and when the flash light mode is selected by the operation mode switching means, the display mode is selected by the display mode switching means. The present invention is further provided with a control means for displaying data corresponding to the aperture value on the display section of the display means, regardless of the mode in which the display means is set. Function Therefore, according to the exposure meter of the present invention, in steady light measurement, data corresponding to the aperture value (AV, F number, etc.) is displayed on a single display section according to the mode switching of the display mode switching means. Selectively display data (EV) corresponding to the value. Further, when the flash light mode is selected, the control means displays data corresponding to the aperture value on the display section regardless of the mode selected by the display mode switching means. Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In Figure 1, 1 is the CPU (central processing unit),
2 is a ROM (read only memory) in which instructions and data are stored; 3 is an I/O port (input/output port); each of these units 1, 2, and 3 is a microcomputer. Reference numeral 4 designates a photometric circuit that outputs the apex value BV of the brightness of the subject, and uses, for example, a circuit in which a capacitor C ₀ is connected to one of diodes D ₁ and D ₂ having the same characteristics as shown in FIG. 5 is an A-D converter circuit that converts the analog signal from the photometric circuit 4 into a digital signal, and the digital value is input through the input port 3.
Added to CPU. 6 is a digital signal corresponding to the apex value TV of the set shutter speed;
A setting circuit outputs a digital signal corresponding to the apex value SV of the set film sensitivity to the CPU 1 through the input port 3, and 7 outputs the aperture opening value output from the I/O port 3 in the form of a binary coded decimal number. A tecoder 8 converts the displayed signal into a signal for 7-segment display, and 8 is a display device that displays the aperture opening value in digital segment format, and also displays over/under when the aperture opening value etc. exceeds a predetermined range. be. The instructions shown in Figure 2 are written in ROM2, and the above microcomputer uses this ROM2.
Controlled by instructions. Further, in this ROM 2, values corresponding to apex values of photometric quantities as shown in Tables 1 to 3, and data such as the aperture opening value and shutter speed are written. In each of the above tables, H indicates that the number is in hexadecimal. That is, for example, referring to Table 1,
AV is a value corresponding to the apex value of the open aperture value, F number is the open aperture value, and AVAdd indicates the address where the corresponding open aperture value is stored on the ROM. Note that K ₂ is an appropriate constant. That is, for example, when the AV value "5" is calculated in the CPU 1 by a signal from the photometry circuit 4, the address K ₂ +5 of the ROM 2 is designated, and the F value 5.6 stored at that address is read out. Next, the operation will be explained according to FIG. First, the analog signal corresponding to the apex value BV of the subject brightness from the photometry circuit 4 is converted into a digital signal by the A-D converter 5, and the data is input to the CPU 1.
Next, digital signals are input corresponding to the set shutter speed TV and set film sensitivity SV, which are respectively expressed as apex values, and the apex calculation of 10・AV = (BV + SV - TV) is performed using registers in CPU 1. conduct. Next, the calculated 10・AV
is the display range of Table 3 010・AV＜140( _00H
10.AV<8C _H ), and if it is over or under, the display device 8 displays over or under, respectively, and then the instruction flow ends. If 10・AV is within the display range, the command 10・AV÷10 is executed. As a result, the specific command is to first set a register in CPU1 to _00H and then set it to 10.
Compare AV and 0A _H , and when 10・AV0A _H , 00 _H
Add 1 to the contents of the register where was written and get 10・
Execute AV−0A _H , compare 10・AV−0A _H and 0A _H again, and when 10・AV−0A _H 0A _H , add 1 to the contents of the register where 01 _H is written. When repeated, 10・AV−n・(0A _H )<0A _H
, the content n of the register where 00 _H was first written becomes the quotient of 10・AV÷10, and 10・AV−
n・(0A _H ) is the remainder. That is, n is a value corresponding to the integer part of the apex value of the open aperture value,
10・AV−n(0A _H ) is the apex value of the aperture opening value in units of 0.1EV [10・AV−n(0A _H )=(AV−n)・
10]. This apex value of the aperture opening value in units of 0.1 EV is added to the decoder 7. The output of the decoder 7 is then applied to the display device 8, and the aperture opening value in units of 0.1 EV is digitally displayed. As mentioned above, the decimal part of the apex value of the aperture opening value obtained from CPU 1 is in the form of 10·(AV-n), which is any number from 0 to 9, and is converted into a binary number. BCD code (binary coded decimal number)
Therefore, a general-purpose decoder 7 can be used as is. Next, it is determined whether the value of n is larger or smaller than _06H , and if _n06H , a decimal point is displayed on the display device 8 and the process moves to the next instruction. Also, if n> _06H , the program moves directly to the next instruction. Next, set the value of n to a constant
Add K ₂ to specify the address of ROM2. ROM2
At this address, the data of the aperture opening value (F number) in BCD code is stored, for example, n=
3, K ₂ +03 _H is specified and the address is
A BCD code "0010 1000" with an aperture opening value of 2.8 corresponding to AV=3 is stored. This stored data is read into CPU1. This data is then applied to the display device 8 from the input/output port 3 via the decoder 7, the aperture opening value is digitally displayed, and this instruction flow ends. FIG. 3 is a perspective view of the external appearance of a light meter to which the present invention is applied. Reference numeral 10 denotes a light receiving section, and 11 a photometry mode selection device, which switches the pointer to the D side when photometry is performed using the incident light method, and to the B side when photometry is performed using the reflected light method.
12 is a display mode switching device that selects whether to display the aperture open value or EV value when measuring ambient light, and 13 is a 7-segment display that displays the aperture open value or EV value. Display section, 14
is a display unit that displays AV or EV values in 0.1 EV units with a 7-segment display; 15 is an over-display device that lights up when the photometric limit is exceeded or the display limit is exceeded; 16 is an over-display device that lights up when the photometric limit is exceeded; 17 is a two-stage selector switch that switches the power on/off and the photometry start signal in stages; pressing the first stage supplies power to the internal circuit. At the same time, when connected to steady light photometry or a strobe using a cord, the second press generates a signal to start photometry. 18 is an operation mode selection device;
When dial position A is switched to the index position, it is set to white light metering mode, and when dial position C is switched, terminal 24 and strobe are connected with the synchro cord, and switch 17
The second press of the button causes the strobe to fire and starts metering at the same time. When you switch to N, you switch to the non-code metering mode where metering starts at the rise of the strobe light. When you switch to M, you can change the time. This is a multi-type metering mode that measures the total amount of strobe light emitted at intervals. 19 is a display section that displays the shutter speed set by the shutter speed setting member 20; 21 is a display section that displays the shutter speed set by the shutter speed setting member 20;
00, 2 to 30 seconds), an erroneous setting display device lights up before the start of photometry. Reference numeral 22 is a display section that displays the film sensitivity set by the film sensitivity setting member 23. FIG. 4 shows a block circuit to which this invention is applied, which is incorporated in the exposure meter of FIG. Blocks that are the same as in FIG. 1 are given the same reference numerals. 30 is a light receiving element that receives light emitted from a strobe (not shown);
31 is a strobe light detection circuit that outputs a pulse at the rising edge of the strobe light, and is connected to terminal 31 except during photometry.
A and 31b are electrically connected to bypass the output current of the light receiving element 30, and during photometry, the terminals are electrically disconnected and the output current of the light receiving element 30 is supplied to the photometric circuit 4. This photometry circuit 4 receives a photometry start signal from the terminal C of the I/O port 3 or a signal from the detection circuit 31 and sends the light receiving element 3 to a capacitor provided in the photometry circuit 4.
The output current of 0 is integrated, and the detection circuit 3 is used during photometry operation.
Outputs a signal that interrupts 1. Then, photometry is stopped by a signal from terminal b of I/O port 3 of the microcomputer, and at the same time, a signal is output that makes the terminals 31a and 31b of the detection circuit 31 conductive, and a signal from terminal b' is used to start the photometry circuit. discharge the charge of the capacitor. For the A-D converter circuit 5, for example, only the analog section may be externally connected to the microcomputer, and the digital circuit such as the counter section may use a register or the like within the CPU 1. 32 is a strobe that receives a signal from terminal C via a synchro terminal (FIG. 3, 24) and a synchro cord and emits light. 33 is a TV setting circuit which outputs a digital signal corresponding to the apex value TV of the shutter speed set by the shutter speed setting member 20 of FIG. 3 to the I/O port 3; 34;
is an SV setting circuit which outputs a digital signal corresponding to the film sensitivity apex value SV set by the film sensitivity setting member 23 of FIG. 35 are the photometry mode selection device 11, display mode selection device 12, and operation mode selection device 18 shown in FIG.
a mode setting circuit 37 that outputs a digital signal corresponding to the selected mode to the I/O port 3;
3 is the second step of the switch 17 shown in FIG. This is a display circuit of the display section 14. 7-1, 7-2, 7-3
are decoders that convert the binary coded decimal numbers sent from the CPU 1 into codes for the 7-segment display tube, and the decoded signals of the decoders 7-1, 7-2, and 7-3 are displayed as the aperture opening value or EV value display section 1. It is applied to the segment display section 82 for the digit, the segment display section 83 for the second digit, and the decimal point display section 84 for AV or EV. The ROM 2 stores flowcharts shown in FIGS. 5-1 and 5-2. In addition, ROM2 contains the F value, 10・SV value, and TVI shown in Tables 1 to 3.
Remembers the value. As mentioned above, Table 1 is
Table 2 shows the value K ₁ +SVX corresponding to the signal SVX from the apex value SV setting circuit 34 of the set film sensitivity.
(K ₁ ; constant) is an address in ROM2, indicating that the value of data 10·SV is stored at that address.
Normally film sensitivity is in units of 1/3 EV, but here it is approximated as 2.0, 2.3, 2.7, 3.0, 3.3, 3.7... The TIME column in Table 3 shows the set shutter speed. TVX corresponds to the output signal of the shutter speed TV setting circuit 33 in FIG. TI indicates the value of the signal corresponding to the integration time of the photometric circuit 4 in Fig. 4, 2 ⁰ : 2 ¹ : 2 ² ...
...: 2 ⁸ . HIAdd indicates an address in ROM2, and is the value obtained by adding a constant _K3 to the value of TVX, indicating that TI is stored at the address indicated by this value. In addition, here the shutter speed is 1/250~1
It is reserved for seconds. TVI is a value for performing apex calculations. In this example, the shutter speed is 1/1000 to 30 seconds, so there are some values where TV is negative, so TVI = 10 · (10 - TV), so all values are positive. It's like this. TVIAdd is the address where TVI is stored by adding the constant _K4 to -TVX. The operation of the circuit shown in FIG. 4 will be explained below in accordance with the flowchart shown in FIG. When the switch 17 shown in FIG. 3 is pushed down one step and a switch (not shown) is turned on, power is supplied to the circuit shown in FIG. 4 and the execution of instructions is started. First, mode discrimination is performed in #1, and A
mode and other operating modes. In the case of natural light metering mode (A mode), the signal corresponding to 1/250 second is set as the integration time (photometering time) in #6.
It is set in the register in CPU1 and moves to instruction #7. Also, when the switch 18 is set to N, M or C mode, input TVX in #2 and determine the set shutter speed in #3.
If it is not set to TVX8, turn on the incorrect setting display device in #4 and return to the start. 0
For TVX8, specify the address of ROM2 with the value of the set shutter speed signal TVX plus the constant _K3 in #5, and send the signal corresponding to 2 ^-TV stored at that address to the register in CPU1. Set #7
It is transmitted to the command of. The operation mode is determined again with the command #7, and N, M
In the mode, the command waits for the rise of the strobe light in #8, and when the detection circuit 31 outputs a pulse at the rise of the strobe light, the process moves to command #11. In addition, when in A or C mode, wait for switch 37 to close in #9,
When the switch 37 is closed, the d terminal is set to "1", the C terminal is set to "1" at #10, and the photometry circuit 4 starts photometry. Also, when in C mode, the strobe starts firing and moves to command #11. In #11, the CPU 1 counts the charging time of the capacitor in the photometric circuit 4. When the count is finished, in #12, the end signal is sent from the CPU 1 to the b terminal, setting the b terminal to "1" and turning on the photometric circuit 4. stop,
Charging of the capacitor in this photometric circuit is stopped. Here, the method of time counting is to set a constant in a register, subtract 1 from this register to determine whether the register is 0, and if it is not 0, repeat the operation of subtracting 1 from the register again. When the contents become 0, 1 is subtracted from the contents of the register set by instruction #5 or #6, and when the contents of the register are not 0, a constant is set in the register again and the operation of subtracting 1 is repeated. In response to the charging time end signal, the photometric circuit 4 applies the capacitor charging value, that is, the analog signal value of the apex value of the photometric amount to the A-D conversion circuit 5;
This analog value is converted to a digital value. The output digital value from this A/D conversion circuit 5 is added to the CPU 1 at #13. Note that this digital value is A-D so that it becomes 10・(BV-TV+α).
The constants of the conversion circuit 5 are selected. Here α is chosen so that the contents of the register do not become negative. Also, multiplying by 10 is displayed in 0.1EV units, so
This is to make the 0.1EV digit an integer. Note that CPU1
It is also possible to use the register inside as a counter for A/D conversion so that the value of the register is the output of the photometric circuit converted into a digital value. The output digital value of the above A-D conversion circuit 5 is
When read into CPU1, the b’ terminal becomes “1” in #14.
This signal discharges the charge in the capacitor of the photometric circuit 4. On the other hand, in #15 the CPU
1, it is determined whether the value of the apex value 10·(BV-TV+α) of the photometric amount added from the A-D conversion circuit 5 exceeds the upper and lower limit values,
If the upper limit has been exceeded, the process proceeds to #16, where the display circuit 81 displays an overage value, and then the instruction ends. If the photometric value (apex value) is below the lower limit, that is, if it is under, the mode is determined in #17, and if it is in N, M, or C mode, the process proceeds to #20, where the display circuit 81 displays under, and the command is issued. finish. When in A mode, proceed to #18 and determine whether TV' is set by command #6 = 10・(10-TV) or TV' is set by command #19, and TV' = 0.
When , the command goes to #20 and the command ends after the under display, and when TV' = 8, the command goes to #19 and after setting the integration time corresponding to TV' = 0, it returns to the command #10 and performs the photometry described above. perform an action. If the photometric value 10・(BV-TV+α) is within the upper and lower limits with the command in #15, then in #21 input the set value SVX from the film sensitivity setting device 34 to the CPU 1 and set it to this SVX. ROM2 with the value added by constant K ₁
Specify the address and read the data corresponding to 10・SV. Then, in #22, from this data and the photometric value above, 10・(BV+SV−TV+α)=10・(AV+α)
The calculation is performed in the register in CPU 1, and then the photometry mode is determined in #23. When in D mode,
In #24, the operation 10.(AV+α-3) is performed and the process moves to instruction #25. If the mode is B, the process directly proceeds to instruction #25. This is because incident light photometry is not affected by the reflectance of the subject compared to reflected light photometry, so the photometry value at the same illuminance is 3EV larger. Determine the operating mode using command #25 in Figure 5-2, and if it is A mode, proceed to command #26 and set
TV' is determined, and when TV' = 8, #27 is 10・(AV+
After calculating α+TV′)=10・(EV+α), the process moves to instruction #28, and when TV′=0, 10・(AV
+α) = 10・(EV+α), so move directly to instruction #28. In #28, it is determined whether 10·(EV+α) is within the display limit, and if it is over or under, the corresponding display is made by the display circuit 81 in #29 or #30, and then the instruction is terminated. If it is within the display limit, determine the display mode in #31. To display the EV value, use #32 to calculate 10・(EV+α)−10・α, and then use #33 to calculate 10・EV÷10.
Among the results of this calculation, data indicating the remainder is added to the display device 84 via the decoder 7-3 at #34. The EV value is then digitally displayed on this display device. On the other hand, in #35, the EV of the above calculation result is
The quotient of the value is corrected in decimal and #36 is sent to the decoder 7-1,
In addition to display circuits 82 and 83 via 7-2, the EV value is displayed as a two-digit digital value in segments. This operation is detailed in the circuit description of FIG. Next, in #37, it is determined whether the switch 37 is closed or not. If the switch 37 is closed, the command returns to the start, and if it is not closed, the instruction ends. If the F value display mode is determined in #31,
Proceeding to #38, the set shutter speed apex value TV, TVX, is input from the setting device 33 to CPU1, and the value obtained by adding the constant _K4 to AVX specifies the address in ROM2, and in #39, the TVI stored at that address is input. =
Load data compatible with 10・(10−TV)
10・(EV+TVI+α)=10・(EV−TV+10+α)
Perform the calculation =10・(AV+10+α). And then #40 is 10・(AV+10+α)−100=10・
Performs the calculation (AV+α) and moves to instruction #41. With instruction #25, when in N or C mode, go directly from #25 to instruction #41, and when in M mode, perform the operation shown in Japanese Patent Application No. 13287-1987 at step #54, Corresponding to the total amount of photometry up to that point.
After calculating 10・(AV+α), move to instruction #41. Next, with instruction #41, the above calculation result 10・(AV+
α), that is, whether the aperture open value (F value) or AV value is within the display limit or not is determined. If it is over the upper limit, the display circuit 81 displays an over value in #42, and if it is under, that is, below the lower limit, it is displayed in #43. The operation mode is determined, and if the mode is A, N, or C, under-display is performed in #44, and the flow of instructions is ended. When in M mode, the under display is performed in #45 and the process returns to the start. If the calculation result is within the display limit, the command #46 performs the calculation of 10·(AV+α)−10α=10·AV. The following commands #47 to #52 cause the display circuits 82 and 8 to display the aperture opening value detailed in the operation explanation in FIG.
3,84. When the display is finished, the operation mode is determined by command #53, and if it is M mode, it returns to the start, if it is N or C mode, the flow of instructions ends, and if it is A mode, it moves to command #37 and switches. It is determined whether the switch 37 is closed, and if the switch 37 is closed, the process returns to the start, and if the switch 37 is open, the flow of instructions ends. As described above, in this embodiment, the natural light (stationary light) photometry mode (A) is set to the operating mode selection device 1.
8, if AV is selected by the display mode switching device 12, F is selected.
The number is displayed on the display section 13, and if EV is selected, the EV value is displayed on the display section 13.
If any other mode (N, M, C), that is, a mode in which flash light is photometered, is selected, the F number is displayed on the display section 13 regardless of the selection of the display mode switching device 12. This is no longer the case when metering flash light.
This is because equation (2) does not hold and the EV value cannot be displayed.

【table】

【table】

【table】

[Table] Effects of the Invention As detailed above, the exposure meter according to the present invention includes a photometer that outputs a photometry signal according to a photometry value, and a film that outputs a film sensitivity signal according to a set film sensitivity. sensitivity setting means; exposure time setting means for outputting an exposure time signal corresponding to the set exposure time; and data or exposure value corresponding to the aperture value based on the photometry signal, the film sensitivity signal and the exposure time signal. a calculation means for calculating data corresponding to the aperture value; a display mode switching means for switching between an aperture value display mode for displaying data corresponding to the aperture value and an exposure value display mode for displaying data corresponding to the exposure value; an operation mode switching means for switching between a flash light mode for measuring light and a steady light mode for measuring constant light; and when the aperture value display mode is selected by the display mode switching means, the aperture value display mode Displays data corresponding to the calculated aperture value, and selectively displays data corresponding to the exposure value calculated by the calculation means when the exposure value display mode is selected. a display means having a single display section for switching contents, and when the flash light mode is selected by the operation mode switching means, regardless of the mode selected by the display mode switching means; The present invention is characterized by comprising a control means for displaying data corresponding to the aperture value on the display section of the display means, and by configuring it in this way, the aperture value can be adjusted with a single display section. Values and exposure values can be selectively displayed, the configuration is simple and compact, and contrast can be easily measured based on exposure values and is easy to understand. Furthermore, with the above configuration, when the flash light mode is selected, data corresponding to the aperture value is displayed on the display section regardless of the mode selected by the display mode switching means.
It is possible to provide a light meter with good operability for the user.

[Brief explanation of drawings]

Fig. 1 is a block circuit diagram showing an embodiment of the present invention, Fig. 2 is a control flowchart used in the embodiment of Fig. 1, and Fig. 3 is a perspective view of a light meter to which the embodiment of Fig. 1 is applied. 4 is a block circuit diagram used in the embodiment of FIG. 3, and FIGS. 5-1 and 5-2 are control flowcharts of the circuit of FIG. 4.
FIG. 6 is a diagram showing an example of a photometric circuit. 1...CPU (Central Processing Unit), 2...ROM, 3
...I/O port, 4...Photometering circuit, 5...A-
D conversion circuit, 6...setting circuit, 7...decoder,
8...Display device.

Claims (1)

[Scope of Claims] 1. Photometering means for outputting a photometry signal according to a photometry value, Film sensitivity setting means for outputting a film sensitivity signal according to a set film sensitivity, and Exposure corresponding to a set exposure time. exposure time setting means for outputting a time signal; calculation means for calculating data corresponding to an aperture value or data corresponding to an exposure value based on the photometric signal, the film sensitivity signal and the exposure time signal; display mode switching means for switching between an aperture value display mode that displays data corresponding to the exposure value and an exposure value display mode that displays data corresponding to the exposure value; a flash light mode that measures flash light; and a constant light mode that measures steady light. an operation mode switching means for switching between the light mode and the light mode; and when the aperture value display mode is selected by the display mode switching means, displaying data corresponding to the aperture value calculated by the calculation means; Display means having a single display section that selectively switches display contents so as to display data corresponding to the exposure value calculated by the calculation means when the exposure value display mode is selected; When the flash light mode is selected by the operation mode switching means, a display corresponding to the aperture value is displayed on the display section of the display means, regardless of the mode selected by the display mode switching means. An exposure meter characterized by comprising: a control means for displaying data;