Camera

A camera includes an entry member which commands spotwise photometric means to effect the entry of spotwise brightness value or values of an object being photographed. A spotwise photometric mode is selected in response to a first operation of the entry member, and the entry of a spotwise brightness value or values occurs in response to a second and subsequent operation of the entry member. Spotwise brightness values and a result of an arithmetic operation performed thereon are nullified in response to the completion of a photographing operation in the spotwise photometric mode while maintaining the spotwise photometric mode. Exposure factors used when controlling an exposure by an automatic exposure control means are stored, thereby enabling a photographing operation or operations to be repeated under the same exposure level as that used during a previous photographing operation, by utilizing such exposure factors.

BACKGROUND OF THE INVENTION 
The present invention relates to a camera, and more particularly, to a 
camera including spotwise photometric means which facilitates taking a 
picture through a spotwise photometry. 
As is well recognized, a photometry used in the prior art practice of 
cameras may be categorized into an average photometry and a spotwise 
photometry. In the average photometry, the brightness level of a 
relatively broad area of an object being photographed is uniformly 
determined, and provides a passable result for ordinary objects. 
Accordingly, almost all conventional cameras having a photometry 
capability employ this technique. By contrast, the brightness level of a 
restricted area of an object being photographed is determined in a 
spotwise manner during the spotwise photometry, and such photometry is 
effectively utilized when it is desired to control the exposure in 
accordance with either a bright or dark area of an object being 
photographed which exhibits a high contrast ratio. However, a disadvantage 
of the spotwise photometry is that a troublesome operation is required and 
that there is a likelihood that a picture may be taken with improper 
exposure. Accordingly, when taking a picture of an ordinary object being 
photographed, the preference of the average photometry over the spotwise 
photometry is assumed. 
It should be realized however that there are a number of objects being 
photographed in actuality which exhibit high levels of contrast ratio 
including an object in the rear light, an object or objects on the stage, 
an object in a composition formed by viewing the exterior through a window 
or the like. The chance to take a picture of an object exhibiting a high 
contrast ratio increases with the improvement in the photographing skill 
of a user. When an object exhibiting a high contrast ratio is photographed 
with a camera which employs the average photometry, the exposure is 
controlled in accordance with an average brightness of the object, and 
hence it is impossible to reflect the intention of a user in composing the 
picture if it is desired to control the exposure in accordance with the 
brightness of either a bright or a dark area of such object. 
In the prior art practice, when it is desired to take a picture of such a 
special object, a so-called spotwise exposure meter having a very limited 
photometry angle is used to determine the brightness of an object being 
photographed at a plurality of locations thereon, and exposure factors to 
be used in taking a picture, such as a diaphragm aperture or an exposure 
period, are determined on the basis of such brightness information as well 
as the intended composition describing which part of the object should be 
taken with a proper exposure and what level should be given to a dark 
area. Where an object being photographed is accessible as when taking a 
picture in a studio, the exposure factors are determined as a result of 
determining the brightness of the object at a plurality of desired 
locations thereon using an exposure meter of incidence type. It will be 
appreciated however that the use of an exposure meter which is separate 
from the camera to perform the spotwise photometry when determining the 
exposure factors represents both a time and labor consuming procedure and 
disadvantageously requires complicated calculation. 
To accommodate for this, a camera is already available which is provided 
with spotwise photometric means and which permits the entry of brightness 
values determined by the spotwise photometric means whenever desired, thus 
enabling an arithmetic operation to be applied to such values to determine 
an exposure level. However, conventional cameras of the kind described are 
constructed so that the entry of brightness values is made by operating an 
entry member and brightness values entered or a resultant value of 
arithmetic operation are cancelled by operating a reset member. Hence, if 
the user forgets to operate the reset member after the completion of a 
photographing operation with the spotwise photometry, a picture with an 
improper exposure, which is not intended by the user, may be taken as a 
result of the previous brightness values being left effective to control 
the exposure during a succeeding operation. Since a photographing 
operation with the spotwise photometry represents a rare instance, a 
camera is also proposed which is arranged to reset the spotwise 
photometric mode automatically after completing a photographing operation 
with the spotwise photometry, while simultaneously cancelling brightness 
values entered. With this camera, an inconvenience is disadvantageously 
caused in that a select member which enables the spotwise photometric mode 
must be operated after each completion of a photographing operation if it 
is desired to take a number of pictures in succession in the spotwise 
photometric mode. 
A camera of the kind described above includes a select member which enables 
the spotwise photometric mode, and an entry member which is operated to 
enter spotwise brightness values. The fact that these members are separate 
results in a troublesome operation and stands in the way to realizing a 
reduced camera size. 
On the other hand, considering a camera of automatic exposure control type, 
the brightness of an object being photographed, which represents one of 
the exposure factors, is determined and is used to calculate other 
exposure factors such as exposure period or diaphragm aperture which are 
effective to produce a proper exposure for the established brightness of 
the object. By operating a shutter or a diaphragm in accordance with the 
exposure factor thus determined, the exposure level is controlled to be 
constant. 
However, in conventional cameras of automatic exposure control type, the 
photometry and the calculation are repeated for each photographing 
operation. Consequently, if it is desired to take pictures over a 
plurality of film frames under the same exposure condition, the exposure 
factor may vary from operation to operation, resulting in a change in the 
exposure condition. 
To accommodate for this, a camera has been proposed which includes a store 
member which may be operated to select an exposure level storage mode. 
When the storage mode is selected, exposure factors are automatically 
stored for use in a next and a subsequent photographing operation. 
However, the camera described immediately above is constructed as a prior 
cocking type which requires the selection of the exposure level storage 
mode before initiating a photographing operation, the exposure condition 
of which should be used as a reference during subsequent photographing 
operations. Hence, if a user desires, after taking a picture, to take 
another picture under the same exposure condition as the first one, such 
cannot be realized. 
SUMMARY OF THE INVENTION 
In view of the foregoing, it is an object of the invention to provide a 
camera which is arranged to nullify brightness values entered as a result 
of the spotwise photometry and a result of arithmetic operation performed 
thereon automatically in response to the completion of a photographing 
operation and which maintains a selected photographing mode. 
It is another object of the invention to provide a camera including a 
single member which may be used to select a spotwise photometric mode and 
to command the entry of a brightness value or values determined by the 
spotwise photometry. 
It is a further object of the invention to provide a camera including means 
for storing exposure factors which are used during an automatic exposure 
control, and a store member which commands the same exposure level as that 
used during a previous photographing operation to be used in a succeeding 
photographing operation, the store member, when operated, establishing an 
exposure level storage mode in which a picture is taken under the same 
exposure level as that used during a photographing operation which 
immediately precedes the selection of the mode. 
In accordance with the invention, brightness values entered as a result of 
the spotwise photometry and a result of arithmetic operation performed 
thereon are automatically nullified in connection with the completion of a 
photographing operation while a selected photographing mode is maintained. 
This eliminates the need to operate a member which nullifies brightness 
values entered each time such entry occurs, and also eliminates the 
likelihood of producing an inadvertent photographing operation as a result 
of failure to operate such member. In addition, the inconvenience that the 
mode select member must be operated each time the spotwise photometry is 
called for is removed. 
Where a single member serves the combined functions of selecting the 
spotwise photometric mode and for commanding the entry of brightness 
values obtained as a result of the spotwise photometry, the entry of the 
brightness values may take place at the same time as the spotwise 
photometric mode is selected. Consequently, there is a likelihood that the 
entry of brightness values takes place while the user is incapable of 
monitoring an exposure level which is determined as a result of the 
spotwise photometry. To accommodate for this possibility, in accordance 
with the invention, when the member is operated for the first time, only 
the selection of the spotwise photometric mode is established, and the 
entry of brightness values is enabled in response to a second and a 
subsequent operation of the member, thus eliminating the likelihood in a 
sophisticated manner. 
Furthermore, when the invention is applied to a camera in which an exposure 
level is automatically controlled, means for storing exposure factors 
which are used during an automatic exposure control, and a store member 
which selects an exposure level storage mode are provided. When the 
exposure level storage mode is selected, a picture is taken under the same 
exposure level as that used during a photographing operation which 
immediately precedes such selection. In this manner, a "retrofit" choice 
of the same exposure level is enabled.

DESCRIPTION OF PREFERRED EMBODIMENT 
Referring to FIG. 1, there is shown a camera according to one embodiment of 
the invention, in plan view. A camera 10 represents a single lens reflex 
camera including a body 1. A lens barrel 2 is detachably mounted centrally 
on the front surface of the body 1, while a pentaprism housing 3 seats 
centrally on the top surface of the body 1 and projects therefrom in the 
form of a triangular roof. As is well known, the barrel 2 internally 
houses and holds a taking lens 4 (see FIG. 2), and rotatably disposed 
around the barrel 2 are a diaphragm presetting ring 5 and a distance 
presetting ring 6 in the sequence named, as viewed from the free end of 
the barrel. A film winding lever 8, a film frame number indicator window 
9, a shutter release button 11, an EE lock knob 13, an entry button 14 and 
an average photometric mode changeover button 15 are disposed on the top 
surface of the body 1 to the left of the pentaprism housing 3. On the 
other hand, a film rewind knob 17, a film speed presetting dial 18, a film 
speed indicator window 19 and an exposure correction knob 22 are disposed 
on the top surface of the body 1 to the right of the housing 3. 
In FIG. 1, numeral 26 represents an operating button which is used when 
mounting the barrel 2 on the body 1, numeral 27 fixtures which are used to 
attach a strap, not shown, to the body 1 and numeral 28 a window frame for 
a finder eyepiece. 
The EE lock knob 13 is rotatably mounted on the pedestal of the shutter 
release button 11, and is normally urged to be brought to and remain 
stationary at a position where a pointer marked thereon is located 
intermediate an index "EE.LOCK" and another mark "CLEAR", both inscribed 
on the top surface of the body 1. The knob 13 may be operated to select an 
exposure level storage mode (hereafter referred to as "EE lock mode") in 
which pictures are taken on a plurality of film frames at an exposure 
level which is once used to take a picture, and to reset the EE lock mode 
or a spotwise photometric mode. The knob 13 is mechanically interlocked 
with an EE lock mode selection switch SW3 (see FIG. 4) and a clear switch 
SW4 (see FIG. 4). The knob 13 may be turned to bring the pointer thereon 
into alignment with the index "EE.LOCK", thereby closing the EE lock mode 
selection switch SW3 to establish the EE lock mode. When the knob 13 is 
turned to bring the pointer into alignment with the index "CLEAR", the 
clear switch SW4 is closed, and the EE lock mode and the spotwise 
photometric mode are reset, thus selecting a normal average photometric 
mode. When the knob 13 is released, it automatically returns to its normal 
position while maintaining the EE lock mode or the average photometric 
mode. 
The entry button 14 is constructed as a self-resetting pushbutton, and is 
mechanically interlocked with an entry switch SW2 (see FIG. 4) to be 
described later. The entry button 14 may be operated for allowing the 
entry of brightness values of an object being photographed which is 
determined through the taking lens 4 by the spotwise photometry, into an 
electrical circuit of the camera 10 for storage. The entry button 14 also 
serves as a member which may be operated to select the spotwise 
photometric mode. When the entry button 14 is depressed for the first time 
under the condition that the average photometric mode is established, the 
entry switch SW2 is closed to select the spotwise photometric mode. In 
response to a second and subsequent depression of the entry button 14, a 
brightness value or values determined by the spotwise photometry are 
sequentially entered for storage. Thus, if the entry button 14 is 
depressed n times consecutively, the spotwise photometric mode is 
established in response to the first depression, and a brightness value is 
entered in response to a second and subsequent depression, thus storing 
brightness values which are (n-1) in total number, in the camera 10. It is 
to be noted that the resetting of the entry button 14 does not terminate 
the spotwise photometric mode, which can only be terminated by depressing 
the average photometric mode changeover button 15 or by turning the knob 
13 into alignment with the index "CLEAR". 
The average photometric mode changeover button 15 is formed by a 
self-resetting pushbutton, and is mechanically interlocked with an average 
photometric mode selection switch SW1 (see FIG. 4) to be described later. 
The changeover button 15 is depressed to effect a switching from the 
spotwise photometric mode to the average photometric mode. 
FIG. 2 shows the optics of the camera 10. As is well known, the optics of a 
single lens reflex camera includes a movable reflecting mirror 31 which is 
rotatably disposed, but which is normally disposed at an angle of 
45.degree. with respect to a taking light path where a finder optical path 
is defined. In this position, light from an object being photographed 
which impinges upon the camera 10 through the taking lens 4 is re-directed 
at right angles upward for incidence upon a finder optics. The finder 
optics comprises a focussing glass 35 which is located at a position which 
is optically conjugate to the photosensitive surface of a photographic 
film 34, a condenser lens 36 disposed immediately above the focussing 
glass 35, a pentaprism 37 disposed directly above the condenser lens 36, 
and a finder eyepiece 38 which is located opposite to the rear end face of 
the pentaprism 37 which represents a light emitting end face thereof. A 
photographing information display 39 defined by a liquid crystal display 
panel of light transmission type, to be described later, is interposed 
between the focussing glass 35 and the condenser lens 36 toward their rear 
edges. 
The central portion of the movable reflecting mirror 31 is processed to 
provide a half mirror or is formed with an array of fully transmitting 
slits, thus defining a semi-transmitting area 31a. A total reflecting 
mirror 32 is mounted in a movable manner on a portion of the back side of 
the mirror 31 which is aligned with the semi-transmitting area 31a so as 
to define a given angle with respect to the mirror 31. The total 
reflecting mirror 32 refelects light from an object being photographed 
which has passed through the semi-transmitting area 31a of the mirror 31 
toward the bottom of the camera 10 where a light receiver 41 is disposed 
for purpose of photometry. Specifically, such light impinges upon the 
light receiver 41 through a bank of condenser lenses 30. 
As shown in FIG. 3, the light receiver 41 is rectangular in configuration, 
and is disposed at an angle toward the front end of the bottom of the body 
1 so as to look up at the total reflecting mirror 32. It comprises a 
substrate 42 of N-type semiconductor, and P-type semiconductor regions 
43a, 43b of an inverted channel configuration and a square configuration, 
respectively, formed on the surface of the substrate 42. A pair of cathode 
electrodes 44a, 44b are applied to the substrate 42 while a pair of anode 
electrodes 45a, 45b are applied to the regions 43a, 43b. The combination 
of the region 43a and the substrate 42 defines a photoelectric transducer 
SPD1 (see FIG. 4) which effects an average photometry of light from an 
object being photographed which is reflected by the mirror 32. The 
combination of the region 43b and the substrate 42 defines another 
photoelectric transducer SPD2 (see FIG. 4) which effects a spotwise 
photometry of light from an object which is reflected by the mirror 32. 
FIG. 4 shows an electrical circuit used in the camera 10 of the invention. 
The circuit includes a reference voltage circuit 60, which develops a 
reference voltage Vref at its output terminal, which is applied to the 
non-inverting inputs of operational amplifiers A1, A4 and to the inverting 
input of an operational amplifier A5. The output terminal of the circuit 
60 is also connected to one end of a variable resistor RV4 which is used 
to choose a voltage corresponding to a diaphragm value, and of another 
variable resistor RV5, which is used to choose a voltage corresponding to 
a film speed and a correction value. The amplifier A1 has its inverting 
input connected to the ground through a semi-fixed resistor RV1 which is 
used to adjust the brightness level. The output of the amplifier A1 is 
connected to the emitter of a transistor Q1 and to the emitters of 
transistors Q2, Q3. The transistor Q1 operates to produce a 
logarithmically compressed voltage, and the transistors Q2 and Q3 operate 
to provide a logarithmic compression of photocurrent. As shown, the 
transistor Q1 is of PNP type, and has its base connected to the 
non-inverting input and its collector connected to the inverting input of 
the amplifier A1. A current I.sub.1 flows through the semi-fixed resistor 
RV1 and through the emitter-collector path of the transistor Q1 which 
makes the potential at the inverting input of the amplifier A1 equal to 
the reference voltage Vref. Thus, 
EQU I.sub.1 =Vref/RV1 (1) 
Accordingly, a voltage V.sub.A1 is developed at the output of the amplifier 
A1 which is defined as follows: 
##EQU1## 
where k represents Boltzmann's constant, T absolute temperature, q unit of 
charge, and I.sub.S the inverse saturation current. 
The transistors Q2 and Q3 which are used to provide a logarithmic 
compression of photocurrent are of PNP type, and the photoelectric 
transducer SPD1 which effects the average photometry is forwardly 
connected between the base and collector of the transistor Q2 while the 
photoelectric transducer SPD2 which effects the spotwise photometry is 
forwardly connected between the base and collector of the transistor Q3. 
The anode of the transducer SPD1 is connected to the inverting input of 
the amplifier A2 while its cathode is connected to the non-inverting input 
thereof. The anode of the transducer SPD2 is connected to the inverting 
input while the cathode thereof is connected to the non-inverting input of 
the amplifier A3. The output of the amplifier A2 is connected to the 
inverting input thereof and is also connected to a first input of a 
multiplexer MPX1 which comprises a plurality of analog switches. The 
output of the amplifier A3 is connected through a resistor R2 to the 
inverting input thereof and to the collector of a transistor Q6, to be 
described later, and also is connected to a second input of the 
multiplexer MPX1. 
The amplifier A5, which has reference voltage Vref applied to its inverting 
input, has its non-inverting input connected to the ground through a 
semi-fixed resistor RV2 which is utilized to adjust the brightness level 
during the spotwise photometry. The output of the amplifier A5 is 
connected to the base of a PNP transistor Q4, the collector of which is 
connected to the non-inverting input of the amplifier A5 and the emitter 
of which is connected to the collector and base of a PNP transistor Q5. An 
operating voltage Vcc is applied to the emitter of the transistor Q5, the 
base of which is connected to the base of a PNP transistor Q6. The 
operating voltage Vcc is also applied to the emitter of the transistor Q6, 
which forms a current mirror circuit together with the transistor Q5. The 
collector of the transistor Q6 is connected to one end of the resistor R2 
as mentioned above. A current I.sub.2 flows through the semi-fixed 
resistor RV2 and through the emitter-collector path of the transistor Q5, 
as defined by the following equation: 
EQU I.sub.2 =Vref/RV2 (3) 
which current is effective to make the voltage at the non-inverting input 
to be equal to the voltage Vref applied to the inverting input of the 
amplifier A5. It will be seen that the current I.sub.2 also flows through 
the transistors Q5 and Q6. 
Assuming that a photocurrent I.sub.p1 passes through transducer SPD1 and 
the transistor Q2, the voltage V.sub.A2 at the output of the amplifier A2 
is given as follows: 
##EQU2## 
The substitution of the equation (2) yields: 
##EQU3## 
Assuming that a photocurrent I.sub.p2 flows through the transducer SPD2 
and the transistor Q3, the voltage V.sub.A3 developed at the output of the 
amplifier A3 is given as follows: 
##EQU4## 
Substituting the equation (2) and rearranging, we have 
##EQU5## 
It will be seen that since the output voltages V.sub.A2, V.sub.A3 from the 
amplifiers A2, A3 do not contain the inverse saturation current I.sub.S, 
in the photometric circuit used in the camera of the present embodiment, 
any influence of the inversed saturation current I.sub.S is eliminated. An 
adjustment of the semi-fixed resistor RV1 causes a change in the magnitude 
of the current I.sub.1, thus allowing the output voltages V.sub.A2, 
V.sub.A3 or the average and the spotwise photometry output to be adjusted. 
Also, an adjustment of the semi-fixed resistor RV2 causes a change in the 
magnitude of the current I.sub.2, allowing the output voltage V.sub.A3, 
namely, the output for the spotwise photometry to be adjusted alone. 
As shown, the amplifier A4, which has its noninverting input connected to 
be supplied with the reference voltage Vref, has its inverting input 
connected to the ground through a resistor R1. A semi-fixed resistor RV3 
is connected between the inverting input and the output of the amplifier 
A4 for developing a voltage which depends on the number of steps assumed 
by the variable resistors RV4, RV5. These variable resistors RV4, RV5 are 
connected in parallel between the output of the amplifier A4 and the 
output terminal of the reference voltage circuit 60. It is to be noted 
that a sliding tap on the variable resistor RV4 is mechanically 
interlocked with a diaphragm, not shown, and is connected to a fifth input 
of the multiplexer MPX1, thus supplying a voltage corresponding to a 
diaphragm value AV thereto. The variable resistor RV5 has a first sliding 
tap which is mechanically interlocked with the film speed presetting dial 
18 (see FIG. 1) and which is connected to a third input of the multiplexer 
MPX1, thus supplying a voltage corresponding to a value of film speed SV 
thereto. The variable resistor RV5 has a second sliding tap which is 
mechanically interlocked with the correction knob 22 (see FIG. 1), and is 
connected to a fourth input of the multiplexer MPX1, thus supplying a 
voltage corresponding to a correction value CV thereto. 
As mentioned previously, the multiplexer MPX1 comprises a plurality of 
analog switches. Its first input receives the output voltage V.sub.A2 from 
the amplifier A2 which corresponds to the brightness value BV1 determined 
by the average photometry. Its second input receives the output voltage 
V.sub.A3 from the amplifier A3 which corresponds to the brightness value 
BV2 determined by the spotwise photometry. Its third input receives the 
voltage on the first tap on the variable resistor RV5 which corresponds to 
a value of film speed SV. Its fourth input receives a voltage on the 
second tap on the variable resistor RV5 which corresponds to a correction 
value CV. Its fifth input receives a voltage on the sliding tap on the 
variable resistor RV4 which corresponds to a diaphragm value AV. The 
multiplexer MPX1 functions to pass one of above five inputs selectively. 
In order to select one of these inputs, it has a control signal input 
which is connected to an output port O2 of a central processing unit (CPU) 
50, which is formed by a microcomputer. The output of the multiplexer MPX1 
is connected to the inverting input of a comparator A6 which forms an A/D 
conversion circuit of sequential conversion type together with a D/A 
converter 58. The converter 58 has its input connected to an output port 
O1 of CPU50, and its output is connected to the non-inverting input of the 
comparator A6. The output of the comparator A6 is connected to an input 
port I7 of CPU50. 
CPU50 has an output port O4 which is connected to the base of a switching 
transistor Q7 through a resistor R3. The transistor Q7 is of NPN type and 
has its emitter connected to the ground and its collector connected 
through the coil of an electromagnet Mg1 to the operating voltage Vcc. 
Thus, the conduction of the transistor controls the energization of the 
electromagnet. CPU50 also has an output port O3 which is connected to the 
input of the photographing information display 39, which comprises a 
liquid crystal display panel. 
CPU50 also has input ports I1 to I6, all of which internally contains a 
pull-down resistor, not shown. It will be seen that each of the input 
ports I1 to I6 is connected to one end of an average photometric mode 
selection switch SW1, the entry switch SW2, an EE lock mode selection 
switch SW3, a clear switch SW4, a release switch SW5 and a trigger switch 
SW6, respectively. All of these switches SW1 to SW6 are normally open, and 
the other end of each of them is connected to receive the operating 
voltage Vcc. The average photometric mode selection switch SW1 is closed 
in response to the depression of the average photometric mode changeover 
switch 15 (see FIG. 1), thereby selecting the average photometric mode. 
The entry switch SW2 is closed in response to the depression of the entry 
button 14 (see FIG. 1), thus selecting the spotwise photometric mode and 
allowing the entry of brightness values. The EE lock mode selection switch 
SW3 is closed in response to the movement of the knob 13 (see FIG. 1) into 
alignment with the index "EE.LOCK", thus selecting the EE lock mode. The 
clear switch SW4 is closed in response to the movement of the knob 13 (see 
FIG. 1) into alignment with the index "CLEAR", thus clearing brightness 
values entered during the spotwise photometric mode and a result of 
arithmetic operation performed thereon, and resetting the spotwise 
photometric mode and the EE lock mode. The release switch SW5 is closed in 
response to the depression of the shutter release button 11 (see FIG. 1) 
and is opened in response to the completion of an exposure process. The 
trigger switch SW6 is closed in response to the upward movement of the 
movable reflecting mirror 31 and is opened in response to the downward 
movement thereof, thus detecting the initiation of an exposure process. 
FIG. 5 is a block diagram showing the internal arrangement of CPU50 which 
constitutes the heart of a control system used in the camera 10 of the 
invention. As shown, a clock generator (CLOCK) 71 produces a pulse, to 
which the operation of CPU50 is referenced. A control circuit (CONT) 72 
controls the entire operation of CPU50. It is necessary that CPU50 
transfers and processes a variety of binary data in proper sequence 
according to a predetermined sequence of programs. To this end, CPU50 must 
have some internal provision to determine which gates therein should be 
enabled and what duration they should be enabled and which flipflops 
should be set or reset, in accordance with the status and input conditions 
relating to CPU50. This task is performed by CONT72. An instruction 
register (INR) 73 temporarily stores the content of a random access memory 
(RAM) 84, to be described later, and CONT72 determines the status of 
various parts of CPU50 in accordance with the content of INR73. A program 
counter (PC) 76 stores the addresses of instructions to be executed in 
order to assure the execution of the programs in a proper sequence. 
Specifically, these addresses increment by one from the lowest to the 
highest memory address in the order of execution. A stack pointer (SP) 77 
temporarily stores the content of PC76, an accumulator (ACC) 79 and an 
index register (IX) 78 or the like without destroying it, in the event an 
interrupt instruction or a jump instruction to a subroutine occurs, for 
allowing such content to be re-used after returning from such instruction. 
IX78 stores the address of an instruction to be executed when an 
instruction is to be executed in an index address form. An arithmetic and 
logical unit (ALU) 81 performs a portion of the execution of an 
instruction which relates to an arithmetic and a logical operation. Thus 
it performs an addition or a subtraction or executes an invert instruction 
which causes the content (either "1" or "0") of a memory to be inverted, 
or forms a logical sum or a logical product of two data. A condition code 
register (CCR) 82 stores a code which is used in the detection of a status 
as a flag when executing an instruction such as a branch instruction which 
requires a determination. The determining function plays an important role 
in CPU50, and when controlling the camera 10 of the invention, the 
execution of a branch instruction is frequently required, which determines 
the status (either "1" or "0") of each input port to change the flow of a 
program to be executed next or to execute the next instruction in the 
sequence without changing the flow. Such execution is performed by 
determining the condition of a flag or flags in CCR82. Specifically, CCR82 
contains a variety of flags including a negative flag which will be set to 
"1" if a result of executing an instruction is negative in 2's complement 
form and which will be set to "0" if the result is positive; a zero flag 
which will be set to "1" if the result is "0" and set to "0" otherwise; an 
overflow flag which will be set to "1" when the result produces an 
overflow in 2's complement form and which will be set to "0" otherwise; a 
carry flag which will be set to "1" if a result of the arithmetic 
operation produces a carry or a borrow from a binary number without sign 
and which will be set to "0" otherwise; etc. A memory buffer register 
(MBR) 75 represents a register into which the content at a specified 
memory address is read in response to a command to read out a memory when 
an address where a read-out should be made is supplied to a storage 
address register (SAR) 74. 
A read only memory (ROM) 83 is sequentially read out by CPU50 to enable the 
execution of successive instructions. A random access memory (RAM) 84 
functions to provide a temporary storage of values produced in the course 
of an arithmetic operation or a result thereof as well as a variety of 
input information. A display random access memory (DRAM) 85 includes a 
plurality of areas which have one-to-one correspondence to individual 
segments of the liquid crystal display panel which forms the photographing 
information display 39 (see FIG. 4). If the content at a specified address 
of DRAM85 is "1", the corresponding segment of the display panel is 
energized or illuminated. A liquid crystal driver circuit (LCDD) 61 drives 
the photographing information display 39 formed by the liquid crystal 
display panel, and includes a plurality of segment lines and common lines. 
An input port assembly (INPP) 88 includes the seven input ports I1 to I7 
mentioned above while an output port assembly (OUTPP) 89 includes the four 
output ports O1 to O4 mentioned above (see FIG. 4). It is to be noted that 
each output from OUTPP89 represents a latched output. 
Briefly summarizing the control action by CPU50, it is to be understood 
that CPU50 repeats a pair of cycles, namely, a fetch cycle which causes an 
instruction stored at an address within a memory which is specified by 
PC76 to be loaded, and an execute cycle in which that instruction is 
executed. Initially, a count in PC76 is transferred to SAR74. 
Simultaneously, PC76 then stores the previous content thereof added with 
one. A read command is issued to the memory after the address is 
transferred to SAR74. The content at the specified address is read into 
MBR75 after a short time delay. The instruction code portion of the 
content is then transferred to INR73. This represents the fetch cycle. 
Then follows the execute cycle, the detail of which depends on the content 
stored in INR73. By way of example, assume that an instruction to load the 
content of the memory into ACC79 (LDA instruction) is transferred to 
INR73. The address portion of the instruction which remains in MBR75 is 
transferred to SAR74, followed by a read command issued to the memory. 
After a short time delay, MBR75 acquires data, which is transferred to 
ACC79, thus terminating the execution of the instruction. 
By way of another example, the execution of a conditional branch 
instruction, which frequently occurs in flow charts to be described later, 
will be described. Assuming that the conditional branch is based on the 
determination of the status of a port, say port A, the content of the port 
A is read into MBR75 during the fetch cycle, in the manner mentioned 
above. It is assumed that the bit at the port A corresponds to the most 
significant bit in the memory. Assuming that an LDA instruction to load 
the content of the memory into ACC79 is supplied to INR73, the content of 
the port A is transferred to ACC79, in the same manner as mentioned above. 
Then PC76 indicates the address of an instruction to be executed next. 
This instruction is stored in MBR75 in the similar manner. Assuming that 
INR73 contains an instruction (ROL instruction) to shift the most 
significant bit of ACC79 to the carry flag of CCR82, the status, either 
"0" or "1", of the port A will be stored in the carry flag during the next 
execute cycle. Then an instruction (BCS instruction) to make a branch if 
the carry flag is "1" and to execute a next instruction in the program 
otherwise is executed by determining the status of the carry flag. In this 
manner, the intended purpose is served. In this example, three 
instructions including LDA, ROL and BCS have been used in combination. In 
this manner, by utilizing an arbitrary combination of as many as several 
tens of instructions, any desired control can be achieved. 
Flow charts shown in FIGS. 11 to 16 and to be described later do not 
indicate the specific use of various blocks shown in FIG. 5 to execute 
each of the programs in machine language, but it should be understood that 
instructions for transfer, addition, subtraction and the like which appear 
in the programs can be simply implemented in known manner. 
FIGS. 6 to 10 illustrate several manners of display provided by the 
photographing information display 39. As mentioned previously, the display 
39 is formed by a liquid crystal display panel which is known in itself, 
and comprises a plurality of electrodes representing exposure periods from 
"1" to "2000", a linear array of horizontally elongate segment electrodes 
which are disposed directly above the exposure period electrodes for 
displaying a bar, a linear horizontal array of diamond-shaped segment 
electrodes disposed directly above the segment electrodes and which 
display a point or points, and "SPOT" and "MEMO" electrodes. Each 
electrode is transparent, whereby the display 39 is of light transmission 
type. The segment electrodes which display a bar are used to indicate an 
exposure period corresponding to the average brightness during the average 
photometric mode or corresponding to an arithmetic mean of brightness 
values during the spotwise photometric mode. The segment electrodes which 
display a point or points are used to indicate an exposure period which 
corresponds to each the brightness values during the spotwise photometric 
mode. "SPOT" electrode indicates that the spotwise photometric mode has 
been selected while "MEMO" electrode indicates that the EE lock mode has 
been selected. 
As mentioned previously, each electrode has an associated area in DRAM85 
(see FIG. 5) in one-to-one correspondence. Voltages are selectively 
applied to the electrodes in accordance with the content of these areas, 
thus displaying a shutter speed index, a bar representing an exposure 
period TV or a point representing an exposure period. It should be 
understood that the display produced by the display 39 represents a 
latched display, and hence once a segment is displayed, the display of 
that segment cannot be cleared unless the content of the corresponding 
area is changed. 
It is to be noted that in the flow charts shown in FIGS. 11 to 16, a 
clearing operation for an area or areas which takes place before an 
updated display is produced is not specifically indicated, but that such 
clearing operation takes place in a program which effects a basic display, 
a bar display or a point display. The content of an area is updated at a 
high speed corresponding to several tens of microseconds, and hence no 
flickering occurs if segments which need not be changed are momentarily 
cleared. 
Before describing the operation of the camera 10, several photographing 
modes used in the camera 10 will be generally described. The camera 10 can 
be operated in either average photometric mode or spotwise photometric 
mode. In the average photometric mode, a photographing operation is 
controlled on the basis of an average brightness value which is obtained 
by the photometry of an object being photographed over a relatively broad 
area. The spotwise photometric mode is selected by the depression of the 
entry button 14 under the condition that the average photometric mode is 
established. The first depression of the entry button 14 only changes the 
photographing mode, without accompanying the entry of any brightness 
value. During a second and subsequent depression of the entry button 14, 
successive brightness values are entered, and when the shutter is 
released, a photographing operation takes place at an exposure level which 
is determined on the basis of an arithmetic mean of brightness values. In 
either average or spotwise photometric mode, the EE lock mode can be 
selected. The EE lock mode is selected by turning the EE lock knob 13 (see 
FIG. 1) into alignment with the index "EE.LOCK" to thereby close the EE 
lock switch SW3 (see FIG. 4), after turning on the camera 10 and after 
performing at least one photographing operation. During subsequent 
photographing operations, pictures can be taken as many times as desired 
under the same exposure level as that used during the photographing 
operation which took place before the EE lock switch SW3 is closed. 
The operation of the camera 10 will now be described with reference to flow 
charts shown in FIGS. 11 to 16. In construing these flow charts, it should 
be noted that MX (X being an arbitrary number) represents a memory 
address, (MX) the content of a memory at an address MX, and ".rarw." a 
transfer operation. Thus, for example, "MA1.rarw.0" means the storage of 
"0" in a memory at an address MA1. Also, "MA1.rarw.(MA3)" means the 
transfer of the content of a memory at an address MA3 into a memory at an 
address MA1. 
Initially, when the camera 10 is turned on, the operating voltage is 
supplied to the electrical circuit shown in FIG. 4. In CPU50, the program 
starts from a mode determining flow chart shown in FIG. 11. Initially, in 
a subroutine SUB I, various flags and memories are initialized. As shown 
in FIG. 15, "0" is stored in a flag MA1 in order to initialize a spotwise 
mode detecting flag MA1. "0" is stored in a similar flag MA2 in order to 
initialize a spotwise entry detecting flag MA2. Then "-1" is stored in a 
memory M6 in order to initialize a number of entries in memory M6. "0" is 
stored in a flag ME1 in order to initialize an EE lock detecting flag ME1. 
Returning to the mode determining flow chart shown in FIG. 11, "0" is 
stored in an EE lock enable flag ME2 in order to initialize it. The 
purpose of the flag ME2 is to prevent the selection of the EE lock mode 
unless at least one photographing operation has taken place after the 
camera 10 is turned on. 
It is then determined if the EE lock knob 13 is turned into alignment with 
the index "CLEAR" by a decision block to see if I4=1. If the knob is 
turned in this manner and the clear switch SW4 is turned on, I4=1. Hence, 
the program makes an exit from this decision block through YES (which is 
indicated by Y on the flow chart), branching into the subroutine SUB I 
where various flags and memory are cleared, followed by the decision of 
the EE lock enable flag ME2. On the other hand, if the knob 13 is not 
turned and the clear switch SW4 remains off, I4=0, and hence an exit is 
made from the decision block of I4=1 through NO (which is indicated by N 
on the flow chart), immediately beginning the decision of the flag ME2. 
In this block, a decision is made to see if (ME2)=0. If (ME2)=0, there has 
taken place no photographing operation since the camera has been turned 
on, and hence an exit is made through YES from this block, jumping over 
the next following detection of the EE lock mode (a decision to see if 
I3=1), entering the determination of the average photometric mode (I1=1). 
(1) Assuming that no actuating member has been operated since the camera 10 
has been turned on, it will be seen that the average photometric mode is 
established in the camera 10. Thus, the switch SW1 is off as is the entry 
switch SW2, and hence an exit is made through NO from the decision blocks 
to see if I1=1 and I2=1. "0" is then stored in the entry detecting flag 
MA2 to initialize it, followed by a decision block to see if (MA1)=1, from 
which an exit is made through NO. Thereafter, the program branches to a 
flow chart for the average photometric mode shown in FIG. 12 through 
.circle.2 -- .circle.2 . 
In FIG. 12, a decision is initially made to see if (ME1)=1, thus 
determining if the EE lock mode is established. Since the EE lock mode is 
not established now, an exit is made through NO from this decision, 
followed by a basic display by the display 39. As shown in FIG. 6, the 
basic display represents the display of exposure period or shutter speed 
indices from "1" to "2000". An average brightness value BV1 is then stored 
in a brightness memory M1. This entry takes place by controlling the 
multiplexer MPX1 to derive a voltage corresponding to the average 
brightness value BV1 at the output thereof and passing it through the A/D 
conversion circuit of sequential comparison type, comprising the 
comparator A6, to be fed to the input port I7 in digital form. 
After the entry of the average brightness value BV1, the program branches 
to a subroutine SUB II shown in FIG. 16 where film speed value SV, 
correction value CV and diaphragm value AV are entered in a manner similar 
to that used for entering the average brightness value BV1, thus storing 
them in a film speed memory M2, a correction value memory M3 and a 
diaphragm value memory M4, respectively. The program then returns to the 
flow chart for the average photometric mode shown in FIG. 12 An Apex 
exposure period value TV is calculated according to the formula 
{(M1)+(M2)+(M3)-(M4)}, with a result being stored in an exposure period 
storage area M5. The exposure period value TV (M5) is then displayed in a 
bar form by the display 39 (see FIG. 6). 
A decision then follows to see if I5=1, thus determining if a shutter 
release has taken place. If not, an exit is made through NO from this 
decision block, followed by the execution of an interval instruction and 
thereafter returning to the mode determining flow chart shown in FIG. 11 
through .circle.1 -- .circle.1 . Thus, unless the shutter release button 
11 is depressed or other member is operated, the program loops around the 
path mentioned above. The purpose of the interval instruction is to make a 
time adjustment so that one cycle through the program has an execution 
time of about 100 mS, such adjustment being simply achieved with a 
microcomputer processing. 
If the shutter release button is depressed to close the release switch SW5, 
an exit is made through YES from the decision block of I5=1 in FIG. 12, 
thus branching to a flow chart for the shutter release shown in FIG. 13 
through .circle.3 -- .circle.3 . In this flow chart, "1" is initially 
stored in the output port O4. In the electrical circuit shown in FIG. 4, 
the transistor Q7 is then turned on to energize the coil of the 
electromagnet Mg1, thus constraining the second blind of the shutter. The 
content of the brightness value memory M1, or (M1), is then stored in a 
brightness value save memory M10, thus saving the average brightness value 
BV1. This accommodates for the possibility that the next photographing 
operation may be effected in the EE lock mode, which requires that the 
average brightness value BV1 of the present photographing operation to be 
saved. Then the spotwise brightness values which have already been 
entered, the spotwise mode detecting flag MA1 and the number of entries 
are sequentially saved as indicated by (MPN.rarw.(MBN), N=1 to n), 
(MA3.rarw.(MA1)) and (MC1.rarw.(M6)). It will be seen that this has 
significance only if the next photographing operation takes place in the 
spotwise photometric mode, and is of no consequence in the present 
instance in which the average photometric mode is employed. The exposure 
period value TV (M5) which is determined by the Apex calculation is then 
stored in a timer count preset memory MT. A decision is then made to see 
if I6=1, thus determining if the trigger switch SW6 has been closed to 
initiate an exposure process. If the exposure process is initiated, an 
exit is made through YES from this decision block, entering a timer 
counting program in which the count is sequentially counted down from the 
initial preset value (MT) until the memory content (MT) becomes equal to 
"0", whereupon an exit is made through YES from this program, followed by 
storing "0" at the output port O4. Then, in the electrical circuit of FIG. 
4, the transistor Q7 is turned off to deenergize the coil of the 
electromagnet Mg1, thus allowing the second blind of the shutter to begin 
running. In this manner, the exposure process is terminated. Subsequently, 
"1" is stored in the EE lock enable flag ME2, indicating that at least one 
photographing operation has taken place since the camera has been turned 
on, thus enabling the selection of the EE lock mode. Subsequently, "0" is 
stored in the spotwise entry detecting flag MA2, thus resetting it to a 
condition which represents no entry of spotwise data. It will be seen that 
this has significance only when a next photographing operation is to take 
place in the spotwise photometric mode, and has no significance in the 
present instance which employs the average photometric mode. A decision is 
then made to see if (MA1)=1, thus determining if the present photographing 
operation has been made in either the average or the spotwise photometric 
mode. Since it has taken place in the average photometric mode, an exit is 
made through NO from this decision block, followed by the initialization 
of the number of entries in memory M6 by storing "-1" therein. If the 
photographing operation has taken place in the spotwise photometric mode, 
it follows that (MA1)=1, and hence an exit is made through YES, followed 
by storing "0" in the memory M6 so that the entry of a spotwise brightness 
value may take place immediately upon the next depression of the entry 
button 14. The execution of an interval instruction follows. Such interval 
is required to provide a time delay on the order of several tens of 
milliseconds after the completion of the exposure process until the 
movable reflecting mirror 31 completes its downward movement to allow the 
next photometry to be initiated in actuality. The program then returns to 
the mode determining flow chart shown in FIG. 11 through .circle.1 -- 
.circle.1 , thus looping around the path described above. 
It is to be noted that the depression of the average photometric mode 
changeover button 15 when the spotwise photometric mode is established 
also establishes the average photometric mode in the camera 10. In this 
instance, in the mode determining flow chart of FIG. 11, as the selection 
switch SW1 is turned on, it follows that I1=1. Hence, an exit is made 
through YES from the decision block to see if I1=1, followed by the 
initialization of the spotwise mode detecting flag MA1 and the entry 
detecting flag MA2 by storing "0" in each of them. Subsequently, an exit 
is made through .circle.2 -- .circle.2 , thus branching to the flow chart 
for the average photometric mode shown in FIG. 12. Thus, in a manner 
similar to that mentioned above, the program loops around the path, 
providing a bar display of the exposure period value TV based on the 
average brightness value BV1, by means of the display 39 (see FIG. 6). It 
is to be noted that when the changeover button 15 is released, since the 
average photometric mode selection switch SW1 is formed by a 
self-resetting switch, it follows that I1 is unequal to 1, but since the 
content of the spotwise mode detecting flag MA1 is once set to "0", an 
exit is made through NO from the decision block to see if (MA1)=1, 
branching to the flow chart for the average photometric mode shown in FIG. 
12 through .circle.2 -- .circle.2 , in the similar manner as mentioned 
above. 
(2) Under the condition that the average photometric mode is established, 
the EE lock knob 13 may be turned to bring the pointer thereon into 
alignment with the index "EE.LOCK", thereby establishing the EE lock 
during the average photometric mode. This presumes that at least one 
photographing operation has taken place since the camera has been turned 
on and the EE lock enable flag ME2 has "1" as its content. Consequently, 
in the flow chart of FIG. 11, an exit is made through NO from the decision 
block to see if (ME2)=0, followed by a decision to see if I3=1. If no 
photographing operation has taken place since the camera has been turned 
on, the flag ME2 remains to be "0" even if the knob 13 is turned to bring 
the pointer thereon into alignment with the index "EE.LOCK", and hence the 
decision block to see if I3=1 is skipped over, thus avoiding the selection 
of the EE lock mode. When I3=1, the EE lock mode selection switch SW3 is 
turned on, and hence an exit is made through YES from this decision block. 
"1" is stored in the EE lock detecting flag ME1. If the knob 13 is 
subsequently released and the selection switch SW3 is turned off under the 
influence of the bias applied thereto, the EE lock mode remains 
maintained. The content (MC1) of the number of entries memory MC1 is 
transferred to the number of entry memory M6 and the content (MA3) of a 
mode storing flag MA3 which enables the EE lock is transferred to the 
spotwise mode detecting flag MA1. It will be understood that these 
operations have significance only when a previous photographing operation 
has taken place in the spotwise photometric mode, but has no significance 
in the present instance where the operation took place in the average 
photometric mode. If the EE lock is selected during the average 
photometric mode and a previous photographing operation has taken place in 
the spotwise photometric mode, the next photographing operation occurs 
with the EE lock in the spotwise photometric mode, in the same manner as 
the selection of the EE lock during the spotwise photometric mode, which 
will be described in detail later. 
Then follow the decisions to see if I1=1 and I2=2. It will be appreciated 
that it is normally not imaginable that the EE knob 13, the entry button 
14 and the average photometric mode changeover button 15 are operated 
simultaneously. Thus it may be presumed that the switches SW1 and SW2 are 
off, and hence an exit is made from these decisions through NO, followed 
by storing "0" in the entry detecting flag MA2. Subsequently, an exit is 
made through NO from the decision to see if (MA1)=1, thus branching to the 
flow chart for the average photometric mode shown in FIG. 12 through 
.circle.2 -- .circle.2 . In this flow chart, the decision to see if 
(ME1)=1 determines if the EE lock mode is selected. Since this mode is 
selected now, an exit is made through YES from this decision block, 
followed by the basic display. As shown in FIG. 7, the basic display 
includes the display of exposure period indices from "1" to "2000" and the 
index "MEMO". The content (M10) of a brightness value saves memory M10, 
that is, the average brightness value BV1 during the previous 
photographing operation, is restored in the brightness value memory M1 in 
order to permit the same exposure level to be used as that used during the 
previous photographing operation. Subsequently, the film speed value SV, 
correction value CV and diaphragm value AV are entered, the Apex 
calculation of exposure period value TV (M5) is made and then displayed in 
the bar form (see FIG. 7), in a manner similar to that used during the 
normal, average photometric mode mentioned above under the section (1). In 
other words, in the EE lock mode, the average brightness value BV1 is not 
updated, but the average brightness value BV1 used immediately before the 
EE lock mode is selected is employed, while updating only the film speed 
SV, correction value CV and diaphragm value AV. This means that an 
exposure level used in any photographing operation is maintained constant. 
The depression of the shutter release button 11 triggers a shutter release 
in the normal manner as mentioned above in connection with the average 
photometric mode under section (1). 
(3) Considering the operation during the spotwise photometric mode, it will 
be noted that this mode is selected by the depression of the entry button 
14. Specifically, the depression of the entry button 14 turns the entry 
switch SW2 on, and in the flow chart of FIG. 11, an exit is made through 
YES from the decision block to see if I2=1. Then follows a decision to see 
if (ME1)=1 in order to determine if the EE lock mode is established. 
Assuming that such mode is not selected, an exit is made through NO from 
this decision, whereupon a decision is made to see if (MA2)=1 in order to 
determine whether the depression of the entry button 14 represents the 
entry of any spotwise brightness value. The purpose of this decision will 
be understood when one considers that if the entry of spotwise data is 
detected by seeing if the entry switch SW2 is turned on, the presence of 
such entry will be determined upon each circulation through the flow 
chart, which is avoided by confirming that the entry switch SW2 is turned 
off once after one depression of the entry button and then looking for 
another entry. Before the spotwise photometric mode is selected, the entry 
detecting flag MA2 is initialized to "0", and hence initially the program 
makes its exit through NO from the decision block to see if (MA2)=1. "1" 
is then stored in the spotwise mode detecting flag MA1 and the entry 
detecting flag MA2, respectively, thus keeping in storage the selection of 
the spotwise photometric mode and that the entry of spotwise data must not 
occur unless the entry button 14 is once released. The program then 
branches to the flow chart for the spotwise photometric mode shown in FIG. 
14 through .circle.4 -- .circle.4 . 
In the flow chart of FIG. 14, the basic display initially occurs. As shown 
in FIG. 8, the basic display includes the display of exposure period 
indices from "1" to "2000" and the index "SPOT". The number of entries 
memory M6 is then incremented by one, as indicated by M6.rarw.(M6)++1. As 
mentioned previously, the memory M6 is initialized to "-1" when the 
spotwise photometric mode is selected, and hence incrementing it changes 
its content to "0", whereby an exit is made through YES from a next 
following decision to see if (M6)=0. As mentioned previously, the purpose 
of this arrangement is to allow the first depression of the entry button 
14 to change the photographing mode to the spotwise photometric mode 
alone, without accompanying the entry of any brightness value. 
Subsequently, spotwise brightness value BV2 is entered into spotwise 
brightness save memory M7, and then the subroutine SUB II follows to enter 
film speed value SV, correction value CV and diaphragm value AV. The Apex 
calculation of an exposure period value TV (M8) then takes place, and this 
value is displayed by the display 39 in the point form to indicate an 
exposure period for that portion of an object being photographed which is 
currently being determined. Thus, it will be seen that the camera 10 
permits the entry of a spotwise brightness value while allowing a user to 
monitor an exposure level for a portion of the object which is being 
determined. 
A decision then follows to see if I5=1, thus determining if the shutter 
release has taken place. If it has not, an exit is made through NO, and an 
interval instruction is executed, followed by returning to the flow chart 
of FIG. 11 through .circle.1 -- .circle.1 . Normally, the entry switch 
SW2 is maintained on for a duration greater than a time length (about 0.1 
sec) which is required for one cycle of the flow chart. Hence during a 
second pass through the program, after making an exit through YES from the 
decision block of I2=1, an exit is made through YES from the decision 
block of (MA2)=1 this time, thus branching to the flow chart for the 
spotwise photometric mode shown in FIG. 14 through .circle.5 -- .circle.5 
. Hence, spotwise brightness value BV2 is stored in the spotwise 
brightness value save memory M7 again, and subsequently an exposure period 
for that portion of the object being photographed which is being currently 
determined is displayed in the point form. 
Subsequently when the entry button 14 is released, the entry switch SW2 is 
turned off by a bias applied thereto, whereby I2 becomes unequal to 1. 
Hence, in the flow chart of FIG. 11, an exit is made through NO from the 
decision of I2=1. However, since "1" is stored in the spotwise mode 
detecting flag MA1 during the first pass through the program, an exit is 
made through YES from the decision of (MA1)=1, after initializing the flag 
MA2 by storing "0" therein. An exit is made through NO from the decision 
of (ME1)=1, thus branching to the flow chart for the spotwise photometric 
mode shown in FIG. 14 through .circle.5 -- .circle.5 . The subsequent 
program portion remains the same as when the entry button 14 is depressed. 
When the entry button 14 is depressed again to close the entry switch SW2, 
in the flow chart of FIG. 11, an exit is made through YES from the 
decision of I2=1, and then an exit is made through NO from the decision of 
(MA2)=1, followed by storing "1" in the spotwise mode detecting flag MA1 
and the spotwise entry detecting flag MA2. Subsequently, the program 
branches to the flow chart for the spotwise photometric mode shown in FIG. 
14 through .circle.4 -- .circle.4 . In this flow chart, the basic display 
occurs initially, followed by incrementing the number of entries memory M6 
by one, as indicated by M6.rarw.(M6)+1, whereby the memory M6 has the 
content (M6) of "1". Thus, an exit is made through NO from the following 
decision block to see if (M6)=0, thus storing spotwise brightness value 
BV2 in the brightness value save area MBn where n represents the content 
(M6) of the memory M6. Since (M6)=1 now, the brightness value BV2 is saved 
in a memory at the address MB1. The Subroutine SUB II then follows to 
enter the film speed value SV, correction value CV and diaphragm value AV. 
The Apex calculation of an exposure period TV corresponding to the 
spotwise brightness value BV2 then takes place, and this value is stored 
in the corresponding exposure period save area MSN. The exposure period 
value TV is displayed by the display 39 in the point form. An arithmetic 
means of exposure period values TV is then calculated according to 
##EQU6## 
and is stored in an exposure period save memory M5. It will be seen that 
since the single entry has been made, the brightness value BV2 itself 
represents the mean value. This mean value is then displayed by the 
display 39 in bar form. Subsequently, the brightness value BV2 is stored 
in the spotwise brightness value save memory M7. Subsequently, an exposure 
period value for a portion of the object being photographed which is being 
currently determined is displayed in bar form, in a similar manner. 
A decision then follows to see if I5=1, determining if the shutter release 
has taken place. If it has not, an exit is made through NO, and an 
interval instruction is executed to return to the flow chart for the mode 
determination shown in FIG. 11 through .circle.1 -- .circle.1 . During a 
second and a subsequent pass through the program, an exit is made through 
YES from the decision of I2=1 and through YES from the decision of 
(MA2)=1, thereby branching to the flow chart for the spotwise photometric 
mode shown in FIG. 14 through .circle.5 -- .circle.5 , in a manner 
similar to that described above in connection with the first depression of 
the entry button 14. When the entry button 14 is released, an exit is made 
through NO from the decision of I2=1 while an exit is made through YES 
from the decision of (MA1)=1, thus branching to the flow chart for the 
spotwise photometric mode shown in FIG. 14 through .circle.5 -- .circle.5 
, in a manner similar to that as mentioned above. 
When the entry button 14 is depressed a plurality of times in this manner, 
it is assured that an exit is made through NO from the decision of (MA2)=1 
during the initial pass through the program when I2=1 applies, thus 
branching to the flow chart for the spotwise photometric mode shown in 
FIG. 14 through .circle.4 -- .circle.4 , thereby incrementing the number 
of entries memory M6 by one as indicated by M6.rarw.(M6)+1. In this 
manner, the content (M6) or the value of n is incremented sequentially, 
thus storing successive brightness values BV2 at the memory which has a 
sequentially incremented address number from MB1 to MBn. It will be seen 
that for each entry of spotwise brightness value, the Apex calculation of 
a corresponding exposure period is repeated according to the formula 
{(MBN)+(M2)+(M3)-(M4), for N=1 to n}, and each exposure period value is 
stored in a corresponding memory of exposure period save area MSN (N=1 to 
n). Each of these exposure period values TV is displayed by the display 39 
in point form. (FIG. 9 illustrates three entries of spotwise brightness 
values.) Subsequently, an arithmetic mean of exposure period values TV is 
calculated according to 
##EQU7## 
and the result is stored in the exposure period save memory M5. The mean 
value (M5) is displayed by the display 39 in bar form (see FIG. 9). 
Subsequently, spotwise brightness value BV2 which is being currently 
determined is entered, and a corresponding exposure period value TV is 
displayed in point form. The point display shifts as the camera 10 is 
moved or a change occurs in the brightness of an object being 
photographed, and therefore, can be distinguihsed from the point display 
of the exposure period corresponding to the spotwise brightness values 
which have already been entered. 
If the shutter release button 11 is depressed to close the release switch 
SW5, in the flow chart for the spotwise photometric mode shown in FIG. 14, 
an exit is made through YES from the decision of I5=1, thus making a 
decision to see if (M6)=0. The purpose of making such a decision is to 
enable a photographing operation in the average photometric mode rather 
than the spotwise photometric mode if the shutter release button 11 is 
depressed when the spotwise photometric mode is selected, but when there 
is no entry of a spotwise brightness value. Specifically, if no entry of a 
spotwise brightness value has taken place, the number of entries memory M6 
has a count of "0", whereby an exit is made through YES from the decision 
of (M6)=0, thus causing the program to return once to the flow chart of 
FIG. 11 through .circle.6 -- .circle.6 . Then, the spotwise mode 
detecting flag MA1 and the entry detecting flag MA2 are initialized to 
"0", and thereafter the program enters the flow chart for the average 
photometric mode shown in FIG. 12 through .circle.2 -- .circle.2 , thus 
allowing the shutter release to take place in quite the same manner as in 
the average photometric mode. It is to be noted that although an exposure 
period value TV according to the average photometry is calculated after 
the depression of the shutter release button 11, and then the flow chart 
for the shutter release shown in FIG. 13 is re-entered to initiate an 
exposure process, such processing operation is completed within a time 
interval of several milliseconds, and hence there is no influence 
whatsoever on the actual photographing operation. 
On the other hand, if the shutter release button 11 is depressed when the 
spotwise photometric mode is selected and when there is entry of a 
spotwise photometric value or values, in the flow chart of FIG. 14, an 
exit is made through YES from the decision of I5=1, and an exit is made 
through NO from the decision of (M6)=0, whereby the program directly 
enters the flow chart for the shutter release shown in FIG. 13. Then, the 
shutter release operation which remains the same as that occurring in the 
average photometric mode mentioned in the above section (1) takes place. 
However, in the present photographing operation, the exposure process is 
controlled in accordance with a mean value stored in the save memory M5 
which represents the average of individual spotwise brightness values. 
Also, since the photographing operation is in the spotwise photometric 
mode this time, the program portion relating to the retention or saving of 
spotwise brightness values (MPN.rarw.(MBN), N=1 to n), of spotwise mode 
detecting flag MA1.rarw.(MA3.rarw.(MA1)) and of the number of entries 
(MC1.rarw.(M6)) has significance. Thus, these values used during the 
present photographing operation are saved since it is possible that the 
next photographing operation may take place in the spotwise photometric 
mode with the EE lock. After the termination of the exposure process, "0" 
is stored in the entry detecting flag MA2, thus initializing it to the 
same condition as when the entry button 14 is once released, even though 
the shutter release takes place while maintaining the entry button 14 
depressed. The decision of (MA1)=1 determines that the present 
photographing operation has taken place in the spotwise photometric mode. 
Spotwise brightness values which have been entered are cancelled by 
storing "0" in the number of entries memory M6. The purpose of this is to 
enable the entry of a spotwise brightness value immediately rather than 
changing the photographing mode if the entry button 14 is depressed next, 
inasmuch as the present photographing operation has taken place in the 
spotwise photometric mode. Resetting the content of the number of entries 
memory M6 to "0" causes spotwise brightness values which have been entered 
to be cancelled without clearing the content of brightness value save area 
MBN since the spotwise brightness values which have been entered are 
maintained by the content (M6) of the memory M6, or n. 
(4) The EE lock in the spotwise photometric mode is established by turning 
the knob 13 to bring the pointer thereon into alignment with the index 
"EE.LOCK" when the spotwise photometric mode is selected. This presumes 
that at least one photographing operation has taken place or the content 
(ME2) of the EE lock enable flag ME2 is equal to "1". Thus referring to 
the flow chart of FIG. 11, an exit is made through NO from the decision of 
(ME2)=0, and an exit is made through YES from the decision of I3=1. In a 
similar manner to that used when selecting the EE lock during the average 
photometric mode, mentioned above under the section (2), "1" is stored in 
the EE lock detecting flag ME1, and the content (MC1) of the number of 
entries memory MC1 is transferred to the number of entries memory M6 while 
the content (MA3) of the mode storing flag MA3 is transferred to the 
spotwise mode detecting flag MA1, thus restoring the number of entries 
made during the previous photographing operation and restoring the 
spotwise photometric mode. 
In the following program portion, an exit is made through NO from the 
decision of I1=1, followed by the decision of I2=1. Regardless of an exit 
being made through YES or NO from this decision, an exit is eventually 
made through YES from the decision of (ME1)=1, thus branching to the flow 
chart for the spotwise photometric mode shown in FIG. 14 through 
.circle.7 -- .circle.7 . Then the basic display takes place initially. As 
shown in FIG. 10, the basic display includes the display of exposure 
period indices from "1" to "500", the index "SPOT" and the index "MEMO". 
The subroutine SUB II then follows to enter the film speed value SV, 
correction value CV and diaphragm value AV. The calculation of an exposure 
period corresponding to each of spotwise brightness values which are 
already entered and saved is made according to the formula 
{(MPN)+(M2)+(M3)-(M4), for N=1 to n}, with the result being stored in a 
corresponding memory of the save area MSN (N=1 to n). Each exposure period 
value TV is displayed by the display 39 in the point form. (FIG. 10 
illustrates a case when two brightness values have been previously entered 
and saved.) Subsequently, a mean value of exposure period values TV is 
determined in a similar manner to that used during the normal spotwise 
photometric mode, mentioned above under the section (3), and is displayed 
in the bar form. A brightness value which is being currently determined is 
entered, and the corresponding exposure period is displayed in the point 
form (see FIG. 10). When the shutter release button 11 is depressed, an 
exit is made through YES from the decision of I5=1 as during the normal 
spotwise photometric mode mentioned above under the section (3), thus 
branching to the flow chart for the shutter release of FIG. 13 through 
.circle.3 -- .circle.3 , thus initiating the control of an exposure 
process. Spotwise brightness values which have been entered are saved 
again at this time, thus permitting the performance of as many 
photographing operations as desired under the same exposure condition. 
When the EE lock knob 13 is turned to bring the pointer thereon into 
alignment with the index "CLEAR", the clear switch SW4 is turned on, 
whereby in the flow chart of FIG. 11, an exit is made through YES from the 
decision of I4=1, whereby the subroutine SUB I initializes various flags 
and memories. This terminates the spotwise photometric mode and the EE 
lock mode, whereby the camera 10 automatically returns to the normal 
average photometric mode.