Interchangeable lens camera system - Patent Review 4733258

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BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to an interchangeable lens camera system, and more particularly relates to a camera system in which an intermediate accessory, such as an intermediate ring, a bellows, or the like, which is used for close-up photographing, can be mounted or interposed between an interchangeable objective lens and a camera body, and also relates to an interchangeable lens, a close-up photographic intermediate accessory, and a camera body, which are used in such a camera system.

2. Description of the Prior Art

Conventionally, when an intermediate accessory, such as a tele-converter or the like, is mounted between a camera body and an interchangeable objective lens, it is known that vignetting is caused within the intermediate accessory. Such a technique whereby the amount of vignetting occurring in the intermediate accessory is transmitted from the intermediate accessory to the camera body so as to correct or restrict exposure control, has been proposed, for example, in U.S. Pat. No. 4,326,788.

The present invention recognizes the fact that the foregoing phenomenon of the vignetting is caused in an interchangeable objective lens in the state where the close-up photographic intermediate accessory is used. The phenomenon of such vignetting, is described hereinafter.

In the case where an intermediate accessory is mounted between an interchangeable objective lens and a camera body in order to perform close-up photographing or high magnification photographing, the shortest object distance (which is a distance from an object to be photographed to the object side surface of the interchangeable lens) is shortened in comparison with the cause of using only the interchangeable objective lens. Here, the minimum effective F-number of a photographing optical system is determined in accordance with an object distance, an effective diameter of a constituent component of the optical system, and the largest aperture of a diaphragm (or alternatively, an aperture diameter of an F-number determining ring). Referring to FIG. 12, this state will be explained with a thin single lens corresponding to an interchangeable objective lens of the whole shifting type by way of example.

In FIG. 12, the reference symbol L designates a lens; the reference symbol F.sub..infin. designates a film surface in the infinity focusing condition; and the reference symbol F.sub.N designates a film surface in the nearest focusing condition. In the infinity focusing condition, a parallel light bundle having a width the same as an effective aperture D of the lens L is entered as shown by a solid line in FIG. 12 and focused on the film surface F.sub..infin.. At this time, the minimum effective F-number F.sub.No.eff..infin. is determined in accordance with the following equation (1):

F.sub.No.eff..infin. =1/2 sin .theta..sub.1 ( 1)

where the reference symbol .theta..sub.1 designates an exit angle of outer edge light ray.

In the nearest focusing condition, on the contrary, as shown by a dotted line in FIG. 12, the outer edge light ray emitted from an object O enters the lens L as a divergent light bundle and is focused on the film surface F.sub.N disposed optically behind the film surface F.sub..infin. in the infinity focusing condition. At this time, the minimum effective F-number F.sub.Noeff.N is determined in accordance with an equation of

F.sub.No.eff.N =1/2 sin .theta..sub.2 ( 2)

where the reference symbol .theta..sub.2 designates an exit angle of the outer edge light ray. Since the effective aperture of the thin lens L is equal to the diaphragm aperture in a practical lens system, exposure can be correctly controlled by controlling the diaphragm aperture in the lens system.

In FIG. 12, it is found that in the range from the lens L to the film surface, the outer edge light ray indicated by a dotted line in the nearest focusing condition passes outside (a farther path from an optical axis) the outer edge light ray indicated by a solid line in the infinity focusing condition. That is, this fact shows that in the thick lens system of the whole shifting type, the outer edge light ray in the nearest focusing condition passes outside the outer edge light ray in the infinity focusing condition, in the range behind a diaphragm position, that is, in the range from the diaphragm position to the film surface. Here, ordinarily, an effective diameter of each lens surface of the lens system is determined so that even in the nearest focusing condition of the lens itself, the outer edge light ray is not interrupted. Therefore, the width of the light bundle used in photographing is always controlled by the diaphragm. If the outer edge light ray is interrupted by the effective diameter of the lens disposed behind the diaphragm in the nearest focusing condition, the exit angle .theta..sub.2 is determined by the effective diameter of the lens, so that the outer edge light ray passes inside (a path closer to an optical axis) the diaphragm aperture at the diaphragm position. Therefore, even when the aperture of the diaphragm is started to be decreased from the maximum state, there occurs such a phenomenon that the width of the light bundle is not changed. This phenomenon is referred to as "a phenomenon of partial light blocking aperture". In an ordinary interchangeable objective lens, the effective diameter of each lens surface is determined so that such a phenomenon of partial light blocking aperture is not caused in the whole range of focusing distance of the interchangeable objective lens.

Now, in a camera system of the full aperture light measuring type, as shown in FIG. 13, let an AV value corresponding to the minimum effective F-number be represented by AV.sub.0 ; an AV value corresponding to the desired diaphragm aperture be represented by AV.sub.1 ; and an AV value corresponding to a difference between the width of the outer edge light ray and the diaphragm aperture due to the phenomenon of partial light blocking aperture be represented by .DELTA.AV.sub.0 ; then a diaphragming stroke .DELTA.AV.sub.1 to obtain the desired diaphragm AV.sub.1 is is expressed by the following equation (3):

.DELTA.AV.sub.1 =AV.sub.0 +(AV.sub.1 -AV.sub.0) (3)

Here, the .DELTA.AV.sub.0 is referred to as the "amount of partial light blocking aperture". In the ordinary interchangeable objective lens, the effective diameter of each lens surface is determined so that the amount of partial light blocking aperture .DELTA.AV.sub.0 is a negligibly small value in the whole range of focusing distance thereof and therefore the diaphragming stroke .DELTA.AV.sub.1 is controlled on the basis of the following equation:

.DELTA.AV.sub.1 =AV.sub.1 -AV.sub.0 ( 4)

In the case where the close-up photographic intermediate accessory is mounted between the interchangeable objective lens and the camera body, however, the shortest object distance is considerably shortened in comparison with the case of using only the interchangeable objective lens. This state will be now described with reference to FIGS. 14 and 15.

FIG. 14 shows the case where an intermediate accessory having no lens system, such as an intermediate ring, a bellows, or the like, is used. In the drawing, a solid line indicates the outer edge light bundle in the infinity focusing condition in the state where the intermediate accessory is used. The reference symbol F.sub.N1 designates a film surface in the case of using the intermediate accessory. FIG. 15 shows an intermediate accessory C having a lens system, such as a macro-converter, or the like. In the drawing, a solid line indicates the outer edge light bundle in the infinity focusing condition in the case where no intermediate accessory is used, while a dotted line indicates the outer edge light bundle in the nearest focusing condition in the case where an intermediate accessory is used. The reference symbol F.sub.N2 designates a film surface in the case of using the intermediate accessory.

As will be apparent from FIGS. 14 and 15, the use of an intermediate accessory causes the outer edge light bundle (indicated by the dotted line) in the nearest focusing condition to pass outside the outer edge light bundle (indicated by the solid line) in the infinity focusing condition. In order to prevent such a phenomenon of partial light blocking aperture as described above from occurring even in the state where an intermediate accessory is used, it is necessary that not only the effective diameter of each lens surface of the interchangeable objective lens disposed behind a diaphragm, but also the effective diameter of the intermediate accessory are made large. The ordinary interchangeable objective lens, however, is designed so that no phenomenon of vignetting is caused merely in the case of using only the objective lens without taking the case of using any intermediate accessory into consideration. This is because if the case of using any intermediate accessory is taken into consideration, the diameter of the lens disposed behind the diaphragm of the interchangeable objective lens becomes extremely large and therefore not only the interchangeable objective lens becomes heavy, large, expensive, but also the aberration in off-axial region is determined.

The same applies also to the intermediate accessory, and if it is considered to prevent the phenomenon of partial light blocking aperture from occurring with respect to any interchangeable objective lens, the intermediate accessory per se becomes large and heavy, particulary, in the case where a macroconverter is mounted on the interchangeable objective lens having a large aperture, the light bundle is interrupted in the lens system of the converter, resulting in the phenomenon of the partial light blocking aperture. This is known, for example, in the above-mentioned U.S. Pat. No. 4,326,788.

Conventionally, however, much attention has not been paid on such a phenomenon of vignetting caused by the interruption of the light bundle in the interchangeable objective lens itself because of mounting a close-up photographic intermediate accessory. The present invention has paid attention to such a phenomenon of partial light blocking aperture due to the vignetting caused in an interchangeable lens. Description will be made as to this phenomenon more in detail. FIG. 16 shows the state where an interchangeable objective lens 2 is mounted on a camera body 4, and the diameter of the effective light bundle is controlled by the aperture diameter of a diaphragm S in the interchangeable objective lens 2. FIG. 17 shows the state where an intermediate ring 6 is mounted between the interchangeable objective lens 2 and the camera body 4. In this state, the width of the effective light bundle is defined by the rearmost surface RR of a rear lens group RG in the interchangeable objective lens 2 and the diaphragm S does not define the light bundle in the beginning of stopping down of the diaphragm S. That is, the phenomenon of partial light blocking aperture is caused by the lens system in the interchangeable objective lens 2. The reference symbol F designates a film surface. FIG. 18 shows the state where a macro-converter lens 8 is mounted between the interchangeable objective lens 2 and the camera body 4. Even in this state, the light bundle is interrupted by the rearmost surface RR of the interchangeable objective lens 2, resulting in a similar phenomenon of the partial blocking aperture as described above.

The foregoing phenomenon of partial light blocking aperture in the interchangeable objective lens is caused not only in the lens system of the whole lens shifting type but also in any lens system of any type, such as an internal focusing type, a rear focusing type, and so on. In the case of any type other than the whole lens shifting type, the phenomenon of partial light blocking aperture is generated not only in the range behind the diaphragm position but also in the range in front of the diaphragm position. For example, in the case where a bellows is mounted on the interchangeable objective lens of the front lens shifting type, if the bellows is extended so as to shift the whole of the interchangeable objective lens, the vignetting is caused on a lens surface disposed behind a diaphragm, and in this state, if a front lens of the interchangeable objective lens is shifted, the vignetting is caused on a lens surface disposed in front of the disphragm. That is, the vignetting in the interchangeable objective lens is caused on various different lens surfaces depending on the type of lens, type of focusing, or the like.

Since the amount of the partial light blocking aperture due to the vignetting is not negligibly small, there is such a problem that proper exposure can not be obtained under the exposure operation control performed on the basis of the equation (4) in which the amount of partial light blocking aperture is disregarded.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a camera system in which a proper exposure calculation can be achieved even if there occurs the foregoing vignetting caused in an interchangeable lens in the case where an intermediate accessory is used.

Another object of the present invention is to provide a camera body suitable for the camera system of the type as described above.

A further object of the present invention is to provide an interchangeable objective lens suitable for the camera system of the type as described above.

Still a further object of the present invention is to provide an intermediate accessory suitable for the camera system of the type as described above.

The above and other objects, features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a first embodiment according to the present invention;

FIGS. 2 to 6 are block diagrams each showing a main part of the first embodiment;

FIG. 7 is a time chart showing operations of FIG. 2;

FIG. 8 is a flowchart showing the operation of the first embodiment;

FIG. 9 is a block diagram showing a second embodiment according to the present invention;

FIG. 10 is a longitudinal cross-section showing a main part of a third embodiment according to the present invention;

FIG. 11 is a schematic diagram for explaining the operation of the third embodiment;

FIGS. 12 and 13 are schematic diagrams for explaining a disadvantage caused by a phenomenon of partial light blocking aperture;

FIGS. 14 and 15 are schematic diagrams showing the states where an intermediate ring and a macro-converter are used respectively; and

FIGS. 16 to 18 are schematic diagrams each showing shading of luminous flux caused in an interchangeable objective lens in the case where an intermediate ring or a macro-converter is mounted.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

First, an outline of a first embodiment according to the present invention will be described. Now, the amount of partial light blocking aperture generated due to the vignetting caused in an interchangeable objective lens in the case of using a close-up photographic intermediate accessory is represented by .DELTA.AV.sub.0. Here, if the data concerning .DELTA.AV.sub.0 is stored only in the intermediate accessary, it is impossible to correspond to the changes in .DELTA.AV.sub.0 caused in accordance with changes in magnification of various interchangeable objective lens, zoom objective lens, etc., and on the contrary, if the data are stored only in the interchangeable objective lens, it is impossible to correspond to the changes in .DELTA.AV.sub.0 caused depending on changes in magnification of various close-up photographic intermediate accessory, zoom macro-converter, etc. Accordingly, according to the present invention, the .DELTA.AV.sub.0 is divided into two portions .DELTA.AV.sub.0(L) and .DELTA.AV.sub.0(A) which are then stored in the interchangeable objective lens and the close-up photographic intermediate accessory, respectively. Therefore, the following equation is established:

.DELTA.AV.sub.0 =.DELTA.AV.sub.0(L) +.DELTA.AV.sub.0(A) (5)

Here, the value .DELTA.AV.sub.0(L) changes as the focusing or zooming of the interchangeable objective lens is performed and therefore it will do to arrange such that the data stored in a read only memory (ROM) mya be selectively read out therefrom in accordance with the various changes as described above so as to produce the data as the value of .DELTA.AV.sub.0(L). On the other hand, the value .DELTA.AV.sub.0(A) changes in accordance with various changes in magnification and kind of the intermediate accessory, and therefore it will do to arrange such that the data stored in another ROM may be selectively read out therefrom in accordance with the various changes concerning the intermediate accessary as described above so as to produce the data as the value of .DELTA.AV.sub.0(L).

Let the minimum F-number of the interchangeable objective lens be represented by AV.sub.0(L) (variable value in the case of the zoom lens), and the amount of change in minimum F-number due to the intermediate accessory be represented by AV.sub.0(A) (variable value in the case of an intermediate accessory having a variable magnification), then the following equations are established.

CVC(L)=AV.sub.0(L) +.DELTA.AV.sub.0(L) -X (6)

CVC(A)=AV.sub.0(A) =.DELTA.AV.sub.0(A) +X (7)

Here, the symbol X designates the amount of bias described later. According to the present invention, the value of CVC(L) expressed by the equation (6) is stored in an address into which the value AV.sub.0(L) is stored in the ROM in the interchangeable objective lens. The value of CVC(A) expressed by the equation (7), on the contrary, is stored in an address into which the value AV.sub.0(A) is stored in the ROM in the intermediate accessory.

In the intermediate accessory, the minimum F-number value AV.sub.0(B) and the amount of partial light blocking aperture CVC(B) to be transmitted to the camera body are calculated in accordance with the following equations:

AV.sub.0(B) =AV.sub.0(L) +AV.sub.0(A) (8)

CVC(B)=CVC(L)+CVC(A) (9)

Here, the equation (9) is developed as follows:

CVC(B)=AV.sub.0(L) +.DELTA.AV.sub.0(L) -X+AV.sub.0(A) +.DELTA.AV.sub.0(A) +X (10)

Then, if the equation (10) is arranged and the equations (5) and (8) are substituted into the equation (10), the following equation can be obtained:

CVC(B)=AV.sub.0(B) +.DELTA.AV.sub.0 (11)

Here, CVC(B).gtoreq.AV.sub.0(B) is established.

In the case where the interchangeable objective lens is directly mounted on the camera body without using any intermediate accessory, on the other hand, AV.sub.0(B) and CVC(B) are calculated in accordance with the following equations respectively:

AV.sub.0(B) =AV.sub.0(L) (12) ##EQU1## In this case, even if CVC(B) is transmitted to the camera body, the compensation about the vignetting should not be performed. Then, if the amount of bias X is selected so that an inequality .DELTA.AV.sub.0(L) .ltoreq.x.ltoreq.AV.sub.0(L) +.DELTA.AV.sub.0(L) is satisfied in order to avoid an error due to quantization in the case where the value of CVC(B) becomes negative, the amount of compensation=max {CVC(B), AV.sub.0(B) }-AV.sub.0(B) becomes:

(i) AV.sub.0 in the case of using an intermediate accessory; and

(ii) Zero in the case of using only the interchangeable objective lens.

That is, thus, in the case of (ii), the data concerning the amount of vignetting is never transmitted to the camera body, and it is possible to perform the compensation in accordance with the amount of partial light blocking only in the case of using the intermediate accessory.

FIG. 1 shows an embodiment in which a rear converter 8 with a fixed magnification for close photographing is interposed between a camera body 4 and an interchangeable objective lens 2. The camera body 4 is provided with a microprocessor 10 which controls the operation of the entire system and which is coupled with a setting means 12, an indication device 14, an exposure control means 16, an AF motor control means 18, a light measuring circuit 22, and so forth. In the setting means 12, values representing the photographing conditions, such as a photographing mode, a film sensitivity, a shutter speed, a diaphragm value, and so on, are manually set and the setting means 12 produces signals corresponding to those set values. The display device 14 visibly or audibly indicates the shutter speed and the diaphragm value which are to be automatically controlled in accordance with the results of various arithmetic operations performed in the microprocessor 10, and indicates the selected photographing mode, warning of a blur occurring shutter speed, and whether an in-focus condition has been achieved or not. The exposure control means 16 controls the shutter speed and/or the diaphragm aperture in response to an exposure control output from the microprocessor 10. The AF motor control means 18 drives an AF motor 18a in response to a focus control output from the microprocessor 10. The light measuring circuit 22 measures light from an object to be photographed in response to the closure of a light measuring switch 20 and generates a light measurement output for the focus adjustment and exposure control. An A/D converter 24 is for converting the light measurement output which is the form of an analog signal into a digital signal. An I/O port 26 is for supplying clock pulses to the objective lens 2 and the converter lens 8 and for taking in the signal transmitted from the objective lens 2 directly or via the converter lens 8. A common terminal GND is for grounding, and a terminal VDD is for supplying power therethrough to the circuit of the camera-objective lens 2 and the converter 3 via a buffer 28.

A 3-bit binary counter 30a and 4-bit binary counter 32a are provided in the objective lens 2. The 3-bit binary counter is for counting the clock pulses fed from the I/O port of the microprocessor 10 in the camera body 4 so as to produce a pulse every time when it has counted eight clock pulses, and the 4-bit binary counter 32a is for counting the output pulses produced from the 3-bit binary counter 30a. The output L1 of the 4-bit binary counter 32a is applied to an address decoder 34a the output of which is divided into two signals; that is a signal L2 which designates the higher-order three of eight bits of an address in an ROM 36a, and a signal L4 which designates the lower-order five of the eight bits of the address. The signal L2 is directly given to the ROM 36a, and the signal L4 is given to the ROM 36a via an input selection circuit 38a. In the case a zoom lens is used as the objective lens 2, the input selection circuit 38a receives the output of a decoder 40a which moves relatively to a code plate and reads electrically or optically a code at the position corresponding to a selected zoom ratio. The decoder 40a generates a signal L6 for designating the lower-order five bits of the address in the ROM in accordance with a set zoom ratio or the focal length. The input selection circuit 38a supplies the signal L4 or L6 to the ROM 36a in response to a selection command signal L3 fed from the address decoder 34a. A parallel/series conversion circuit 42a converts the 8-bit data signal from the ROM 36a into serial data and produces the serial data from a data terminal in response to the output from the 3-bit binary counter 30a.

Similarly to the objective lens 2, the converter lens 8 is provided with a 3-bit binary counter 30b, a 4-bit binary counter 32b, an address decoder 34b, an ROM 36b, and a parallel/series conversion circuit 42b, the functions and mutual relationship of which are the same as those in the objective lens 2. The signals having the same suffix correspond to each other. In the ROM 36a of the objective lens 2, the foregoing fixed data to be transmitted to the camera are written in a predetermined address, while in the ROM 36b of the converter lens 8, data necessary for an arithmetic operation to be performed on the data fed from the interchangeable lens 2 are written in a predetermined address. The converter lens 8 is provided therein with an arithmetic circuit 44 which includes, as shown in FIGS. 2, 3, 4, and 5, a serial addition circuit 44a (FIG. 2), a substitution circuit 44b (FIG. 3), a 1-bit left-shifting circuit 44c (FIG. 4) and a 2-bit left-shifting circuit 44 d (FIG. 5). These circuits are selected by a signal A8 from the address decoder 34b in the circuit shown in FIG. 1. The arithmetic circuit 44 is supplied with serially converted signals representing the data from the objective lens 2 as well as serially converted signals representing the arithmetic operation data stored in the ROM of converter 8. The arithmetic circuit 44 performs predetermined arithmetic operations on those signals.

In the circuit of FIG. 6, the data signal DATA.sub.0 from the objective lens 2 and the data signal DATA.sub.1 from the ROM 36b are applied to each of the serial addition circuit 44a, the substitution circuit 44b, the 1-bit left-shifting circuit 44c, and the 2-bit left-shifting circuit 44d, which are connected to an OR gate OR1 via respective AND gates AN1 to AN4. Control signals C1 and C2 contained in the signal A8 are applied to the input terminal of the AND gates AN1 to AN4 directly or via inverters IN1 and IN2. Thus, as shown in Table 1, the output of a desired one of the arithmetic circuits 44a to 44d is selected.

TABLE 1 ______________________________________ Control Input Output Signal Signal C1 C2 D Gate to be opened ______________________________________ 0 0 Q1 AN1 0 1 Q2 AN2 1 0 Q3 AN3 1 1 Q4 AN4 ______________________________________

In the addition circuit 44a as shown in FIG. 2, first, the carry information Cy produced from the Q terminal of a flip-flop FF1 is reset by a reset pulse Res, which is to be input in advance of a clock pulse Cp. Next, the two sets of serial data DATA.sub.0 and DATA.sub.1 fed from the respective ROMs of the objective lens 2 and the converter lens 8 are sequentially respectively applied to the two input terminals A and B in synchronism with the clock pulse CP, two bits after two bits starting from the least significant bit LSB. The output So of a NOR gate NR1 is an exclusive OR A.sym.B. By means of an exclusive NOR NR2, the exclusive OR A.sym.B is further exclusively ORed with Cy and the resultant exclusive OR A.sym.B.sym.Cy is produced from the output NOR gate NR2 as a sum signal S. A carry data output S1 produced from an OR gate OR2 and inverted at the output of the OR gate OR2 is delayed in the D-type flip-flop FF1 by one clock period and produced as the carry data Cy therefrom for performing an adding operation in the next digit. In the example of the waveforms shown in FIG. 7, the signal A is "00011110", the signal B is "00001010", the carry signal is "00011100", and the sum signal S is "00101000".

In the substitution circuit 44b illustrated in FIG. 3, a control input signal C is applied the respective one input terminals of AND gates AN8 and AN9 via an invertor IN5 and directly respectively, the respective other input terminals of the AND gates AN8 and AN9 being supplied with the data inputs A and B respectively, so that an OR gate OR3 produces the signal A when the control input signal C is "0" while produces the signal B when the control input signal C is "1".

FIGS. 4 and 5 show the 1-bit and 2-bit left-shifting circuits 44c and 44d respectively. The 1-bit left-shifting circuit 44c of FIG. 4 comprises a single 2-input addition circuit FA1 two input terminals which are connected to each other to form a single input. The 2-bit left-shifting circuit 44d comprise a first, a second and a third 2-input addition circuits FA2, FA3, and FA4, all the input terminals of the first and second 2-input addition circuits FA2 and FA3 being connected with each other to form a single common input, the respective outputs of the addition circuits FA2 and FA3 being connected the two input terminals of the third addition circuit FA4 so as to derive the output of the 2-bit left-shifting circuit 44d from the output terminal of the third addition circuit FA4.

FIG. 8 shows the operational sequence of the microprocessor illustrated in FIG. 1. The operation of the microprocessor will be described with reference to FIG. 8. When a power supply switch (not shown) of the camera body is turned on, the microprocessor 10 performs initialization. Thereafter, if the light measuring switch 20 is turned on, the microprocessor 10 starts the sequence of reading data of the lens system. First, the power source voltage VDD is initiated to be supplied to the objective lens 2 and the converter lens 8 via the buffer 28. Then, the resetting operation of the circuits of the objective lens 2 and the converter 8 is performed by changing over the level of the reset pulses RES from Low to High. After the reset operation is completed, the microprocessor 10 in the camera body 4 starts the sending out of the clock pulses CP from the I/O port. These clock pulses are simultaneously supplied to both the objective lens 2 and the converter 8. The respective 3-bit binary counters 30a and 30b of the objective lens 2 and the converter 8 produce one pulse every time when they have received eight clock pulses and supply the pulse to the next stage 4-bit binary counters 32a and 32b respectively. The 4-bit binary counters 32a and 32b sequentially generate the signals L1 and A1 respectively as shown in Table 2, in response to the pulses fed from the 3-bit binary counters 30a and 30b respectively, and supplies those signals L1 and A1 to the address decoders 34 a and 34b respectively.

TABLE 2 ______________________________________ Input Output The order of input pulse L1/A1 ______________________________________ 1 0000 2 0001 3 0010 4 0011 5 0100 6 0101 7 0110 8 0111 9 1000 ______________________________________

The address decoders 34a and 34b respectively generate the signals L2 and L4 and A2 and A4 for designating addresses of the ROMs 36a and 36b, in accordance with the signals L1 and A1 from the 4-bit binary counters 32a and 32b. The signals L2 and A2 designate the higher-order three of the eight bits of the respective addresses of the ROMs 36a and 36b, while the signals L4 and A4 respectively designate the lower-order five of the same eight bits of the addresses. In addition, when a zoom lens is used as the objective lens 2, the lower-order five bits of the address of the ROM 36a may be designated by means of the output L6 of the decoder 40a which corresponds to the selected zoom ratio. The selection of the address lower-order 5-bit designating data L4 and L6 is performed in the input selection circuit 38a by means of the output L3 of the address decoder 34a and the output L5 of the input selection circuit 38a designates the address lower-order five bits.

Tables 3 to 5 show the relationships among the respective addresses of the fixed focal length objective lens, the zoom objective lens and the converter lens, and the outputs of the address decoders 34a and 34b.

TABLE 3 ______________________________________ (Fixed focal length objective lens) Address Address higher-order lower-order 3-bits 5-bits L1 L2 L5 Contents of data ______________________________________ 0000 000 00000 Imperfect coupling checking code 0001 000 00001 Minimum F-number 0010 000 00010 Maximum F-number 0011 000 00011 Full aperture light measuring error compensation 0100 000 00100 Release time lag 0101 000 00101 Partial light blocking aperture data 0110 000 00110 Rotational direction of AF motor 0111 000 00111 AF lens position shifting amount conversion coefficient 1000 000 01000 Focal distance ______________________________________

TABLE 4 ______________________________________ (Zoom objective lens) Address Address higher-order Lower-order 3-bits 5-bits L1 L3 L2 L5 Contents of data ______________________________________ 0000 0 000 00000 Imperfect coupling checking code 0001 1 001 .0..0..0..0..0. Minimum F-number 0010 1 010 .0..0..0..0..0. Maximum F-number 0011 0 000 00011 Full aperture light measuring error compensation 0100 0 000 00100 Release time lag 0101 0 000 .0..0..0..0..0. Partial light blocking aperture data 0110 0 000 00110 Rotational direction of AF motor 0111 1 011 .0..0..0..0..0. AF lens position shifting amount conversion coefficient 1000 1 100 .0..0..0..0..0. Focal distance ______________________________________ ".0." represents "0" or "1".

TABLE 5 ______________________________________ (Converter) Ad- Ad- dress dress higher- lower- order order Arith- 3-bits 5-bits metic A1 A2 A4 Contents of data operation C1 C2 ______________________________________ 0000 000 00000 Imperfect Addition 0 0 coupling checking code 0001 000 00001 Minimum Addition 0 0 F-number 0010 000 00010 Maximum Addition 0 0 F-number 0011 000 00011 Full aperture Substi- 0 1 light measuring tution error compensation 0100 000 00100 Release time lag Addition 0 0 0101 000 00101 Partial light Addition 0 1 blocking aperture data 0110 000 00110 Rotational direc- Addition 0 0 tion of AF motor 0111 000 00111 AF lens position Shifting 1(0) 0(1) shifting amount or conversion addition 0 0 coefficient 1000 000 01000 Focal distance Addition 0 0 ______________________________________

The ROMs 36a and 36b transfer the 8-bit data as to the respective addresses designated by the signals L2 and L5 and by the signals A2 and A4, in the order of L1 and A1 to the 8-bit parallel/series conversion circuits 42a and 42b. Each of the 8-bit parallel/series conversion circuits 42a and 42b sequentially converts the received 8-bit parallel data, for example, into 8-bit serial data from the lower-order. The control of the converting timing is performed on the basis of the outputs L7 and A7 from the 3-bit binary counters 30a and 30b respectively. Table 6 shows the logic of the conversion.

TABLE 6 ______________________________________ L7/A7 Output ______________________________________ 0 0 0 0 0 0 0 0 0 0 1 0 0 1 0 0 0 0 0 0 1 0 0 1 0 0 0 0 0 0 1 0 0 0 1 1 0 0 0 0 1 0 0 0 1 0 0 0 0 0 1 0 0 0 0 1 0 1 0 0 1 0 0 0 0 1 1 1 0 0 1 0 0 0 0 0 0 1 1 1 1 0 0 0 0 0 0 0 Highest- Lowest- bit bit ______________________________________

In the sequence as described above, the DATA.sub.0 and DATA.sub.1 are supplied into the arithmetic circuit 44 from the ROM 36a of the objective lens 2 and the ROM 36b of the converter lens 8, respectively. At this stage, outputs of the result of the desired arithmetic operation are selected and produced in accordance with the operation designation data C1 and C2 produced from the address decoder 34b, in the foregoing arrangement as illustrated in FIG. 9 through FIG. 14.

After the microprocessor 10 in the camera body 4 has received the necessary data from the objective lens 2 via the converter 8 through the serial I/O port, the microprocessor 10 reads out the binary coded data as to the photographing mode, the set shutter speed, the diaphragm value, and the apex values Tv, Av, and Sv of film sensitivity, out of the setting device, and starts light measurement by means of the light measuring device 22. The A/D converter section 24 receives the light measurement output as well as a reference voltage (Vref), and the light measurement output is subject to binary quantization. The exposure calculation is performed on the basis of the quantized light measurement value, the minimum and maximum F-numbers derived from the objective lens 2 and the converter 8, and the full aperture light-measuring error compensation amount, in consideration of the photographing mode derived from the setting device 12. The result of the exposure calculation (for example, Av+Tv) is displayed at the display device 14 and transferred to the exposure control device 16. At this stage, the microprocessor 10 releases the inhibition of interruption by the shutter release operation so that the shutter release is enabled to be performed.

The camera then starts the range-finding or focus detecting operation for automatic focusing and determines the amount and direction of the rotation of the AF motor 18a, on the basis of the result of the focus detection, the lens shifting amount coefficient derived from the converter 8, and the AF motor rotational direction data. The result of the determination is sent to the AF motor control device 18 which controls the shifting of the lens in accordance with the input data.

Upon completion of the automatic focusing operation, the camera proceeds to the next step where it waits for interruption by a shutter release operation and proceeds to the interruption processing routine. If the release operation is made before the automatic focusing operation has been completed, the camera proceeds to the interruption processing routine and stops its automatic focusing operation, and then proceeds to the step of the exposure control operation.

The exposure control device 16 performs the control of the camera photographing operation, including the shutter speed and diaphragm control, in accordance with the previously obtained result of the exposure calculation and the release time lag data supplied from the objective lens 2 and converter 8, and a cycle of camera-operation is thus completed.

The following, description relates to the case in which a variable-magnification zoom converter 50 is mounted between objective lens 2 and camera body 4. FIG. 9 shows the block diagram of a circuit therefor. In FIG. 9, the units and control signals which perform the same functions as those in FIG. 1 are referenced correspondingly and there description is omitted. Similarly to the fixed magnifying factor converter lens, the zoom converter 50 will be satisfactorily carried out if it performs arithmetic conversion of the data fed from an objective lens in accordance with the set zoom ratio (magnifying power) of the zoom converter and sends the result to the camera body. In the case of the zoom converter, however, it is not possible to add a fixed value to the received data, since the data to be added or substituted changes in accordance with the zooming. Therefore, a decoder should be used which included, for example, a code plate means movable relative to the code plate for el