JPH02154236A - Camera capable of driving lens during exposure - Google Patents

Abstract

PURPOSE:To obtain a desirable soft focus effect over a wide luminance range by deciding a stop value and a shutter speed so that the diameter of a blur circle may become almost certain value in a camera capable of driving a lens during exposure. CONSTITUTION:A lens driving means 2 has a function for driving a part of a photographic lens 1(focusing lens 1a) during exposure and a special photographic effect such as the soft focus effect is obtained by driving the lens during exposure. An exposure calculation means 4 decides the combination of the spot value Av and the shutter speed Tv so that the diameter of the blur circle is changed as little as possible with the change of the exposure of a main object and the value may become approximate to an optimum value. Therefore, the soft focus effect which is approximate to an optimum is obtained over the wide luminance range.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a camera that can drive the lens between exposures, and for example, uses an eye reflex camera to take fantastic photographs with special photographic effects. It is suitable for

[Prior Art] Conventionally, there have been commercially available cameras in which a fantastic photograph with a special photographic effect can be obtained by driving a focusing lens to defocus while the shutter is open.

There are two types of expressive effects obtained by such a camera that can drive the lens during exposure: a soft focus effect due to an increase in the diameter of the circle of confusion, and an image enlargement/reduction effect due to a change in focal length. The resulting image varies greatly depending on the ratio.

If the contribution of the increase in the diameter of the circle of confusion is very large, a depiction similar to that taken with a soft focus lens will be obtained, and if the contribution of the change in image magnification is very large, a depiction similar to that obtained by shooting with an inter-exposure zoom will be obtained. is obtained.

[Problems to be Solved by the Invention] When obtaining a soft focus effect using a camera capable of driving the lens between exposures as described above, a subjective evaluation of the conditions for obtaining a preferable soft focus effect revealed that the diameter of the circle of confusion was approximately It has been found that the most favorable effect can be obtained with 1500 μIn. However, in conventional AE program diagrams, it is common for both aperture residue and shutter speed to increase as the subject increases by 1 degree.
When such an AE program diagram is used, the brightness range in which a diameter of the circle of confusion close to the above-mentioned optimum value can be obtained is extremely narrow, and there is a problem in that it is not always possible to obtain a desirable soft focus effect. .

The present invention has been made in view of these points, and its purpose is to adjust the aperture value and the aperture value so that a preferable soft focus effect can be obtained over a wide brightness range in a camera that can drive the lens during exposure. The purpose is to enable automatic setting of shutter speed.

[Means for Solving the Problems] In the present invention, in order to solve the above problems, the first
As shown in the figure, in a camera that is equipped with a lens driving means 2 that drives a part of the photographing lens 1 (focusing lens La) during exposure, and obtains special photographic effects by driving the lens during exposure, the brightness By of the main subject is A photometering means 3 for obtaining information, an exposure calculation means 4 for determining an aperture value AV and a shutter speed TV according to the output of the photometry means 3, and an aperture for obtaining the aperture value Ay determined by the exposure calculation means 4. a control means 5 and a shutter speed control means 6 for obtaining the shutter speed Tv determined by the exposure calculation means 4;
The exposure calculation means 4 is characterized in that it is a means for determining the aperture value Ay and the shutter speed TV so that the diameter δ of the circle of confusion becomes a substantially constant value.

Here, according to subjective evaluation, the diameter of the circle of confusion δ is approximately 1500μ
The aperture value AV and shutter speed TV should be kept constant in theory.
By determining this, a desirable soft focus effect can be obtained. To keep the diameter of the circle of confusion δ constant, the aperture value AV expressed in apex value and the shutter speed TV should always be set to 2:-1 as the exposure value EV expressed in apex value increases.
It is necessary to change the ratio of

Note that if the shutter speed TV determined in this way is slower than the limit shutter speed TV at which the lens reaches its end, the formation of a double image is more important than the need to keep the diameter of the circle of confusion δ constant. Therefore, it is preferable to select the limit shutter speed TvL at which the lens reaches its terminal end as the shutter speed TV.

However, when the diameter of the circle of confusion δ is approximately 3000 μm or more, the formation of double images becomes less noticeable, so even if you select a shutter speed TV that is slower than the limit shutter speed TVL at which the lens reaches its terminal end. I do not care.

[Effect] Hereinafter, the operation of the present invention will be explained with reference to FIG.

The lens driving means 2 has an FI function to drive the - part (focusing lens la) of the photographic lens 1 during exposure, and produces a special photographic effect such as a soft focus effect by driving the lens during exposure. be. This lens driving means 2 can also be used as a lens driving means for performing automatic focus adjustment by driving the lens before exposure. The photometer 3 measures the photo area in order to obtain information regarding the brightness Bv of the main subject. The exposure calculation means 4 calculates the exposure amount EV of the main subject based on the brightness Bv of the main subject and the film sensitivity value Sv, and adjusts the aperture value AV and shutter speed TV so that E v = A v + T y. decide.

Then, the aperture control means 5 and shutter speed control means 6 control the aperture and shutter, respectively, so that the aperture value AV and shutter speed Tv are obtained. The R ratio calculating means 4 sets the aperture value AV so that the diameter δ of the circle of confusion does not change as much as possible and becomes a value close to the Ra value (approximately 1500μ circle) with respect to changes in the exposure amount Ev of the main subject. Determine the combination of shutter speed TV. Therefore, in the camera of the present invention, a near-optimal soft focus effect can be obtained over a wide brightness range.

[Example] Figure 2 shows the circuit configuration of a camera as an example of the present invention. performs calculations and sequence control for the entire camera. B
T is a power supply battery, which supplies power to the microcomputer μC and its peripheral circuits. Xtal is an oscillator, and the microcomputer μC operates according to a clock signal determined by this oscillator Xtal.

The microcomputer μC is connected to various peripheral circuits and can exchange information with these peripheral circuits.

First, the DSP is a display circuit that receives display data from the microcomputer μC and performs necessary display.

Display contents include, for example, shutter speed, aperture value, exposure mode (normal mode or fantasy mode),
High brightness warning display, low brightness warning display, film counter,
There are focus indications, focus detection failure indications, etc.

FLC is a flash circuit built into a flash that is detachably attached to the camera body.

The flash is equipped with a flash emission switch FSW, and this flash emission switch FSW has ○
There are two states of N10FF.

The flash circuit FLC transmits information regarding 0N10FF of the flash emission switch FSW to the camera body,
The camera body changes exposure control according to that data. When the flash light emission switch FSW is turned on, the exposure is controlled so that the flash always fires.
When the flash light emission switch FSW is turned off, exposure is controlled so that the flash always does not emit light.

FCC is a flash dimming circuit that controls the amount of flash light.It receives film sensitivity information from film sensitivity reading circuit DXC via microcontroller μC, and measures the amount of flash light incident from the lens according to that information. Then, when the amount of light reaches a predetermined amount, the light emission is stopped.

DXC is a film sensitivity reading circuit that reads film sensitivity information recorded on the film cartridge and transmits it to the microcomputer μC. This information is used for AE calculation in the microcomputer μC.

LMC is a photometry circuit, which divides the photographic screen into a plurality of photometry areas 81 to S6 and performs photometry as shown in FIG.
Sends the necessary data to the microcontroller μC. The microcomputer μC is
The brightness BV of the main subject is calculated as the average brightness of the photometric values in the central photometric areas 84 to S6, and necessary AE calculations are performed to calculate the control aperture value and the control shutter speed.

AFC is an AF control circuit that includes a TTL phase difference detection method focus detection means that photoelectrically converts the subject light that has passed through the photographic lens and detects the defocus amount DF that indicates the amount of defocus from the in-focus position. 0M, which transmits information regarding the focus amount DF to the microcomputer μC, is a motor for driving the focusing lens of the photographing lens, and extends and retracts the lens under the control of the lens drive circuit included in the AF control circuit AFC. , automatic focus adjustment is performed so that the defocus amount DF before exposure becomes zero.

The motor M is also used to drive the focusing lens during exposure to drive the lens during exposure.

The ENC has an encoder, which detects the amount of rotation of the motor M when the motor M for driving the focusing lens is driven, and controls the microcomputer μC according to the predetermined amount of rotation of the motor M.
send a pulse to. The microcomputer μC has a built-in lens position 1 counter for determining the amount of lens extension from the infinity position, which is the most retracted state, as an absolute amount. The value of this lens position counter is expressed as a pulse count number P, and is reset to P = 0 by an internal command when the lens is retracted to an infinite position, and when the lens is extended, an internal command is counted up according to the pulse from the encoder ENC,
When the lens is retracted, an internal command counts down in response to pulses from the encoder ENC. When the lens is extended to the closest position, the value of the lens position counter becomes P=PM. This maximum extension t P M differs depending on the lens, and the microcomputer μC is used as lens-specific information from the lens rotation ILEc.
is loaded into. At the time of focusing, information on the distance to the main subject and the photographing magnification can be calculated from the pulse count number P by this lens position counter. In addition, when out of focus, information on the distance to the main subject and photographing magnification is calculated from the pulse count number P by the lens position counter and the defocus amount DF detected by the AF ff1ll f1 circuit AFC. (See Japanese Patent Application No. 63-206697).

The LEC is a lens circuit built into a photographic lens that is detachably attached to the camera body. The lens circuit LEC stores unique information for each photographing lens, and transmits this information to the microcomputer μC.

Lens-specific information includes maximum extension JI P M
, focal length f, minimum aperture value (so-called open aperture value) AV
o,! Large aperture value AV1. ! , etc. in the conversion coefficients.

Here, the conversion coefficient is a coefficient for converting the defocus amount DF obtained by the AP control circuit AFC into the lens drive amount ΔP (change in pulse count number P). The microcomputer μC performs calculations for automatic exposure control and automatic focus adjustment based on the information transmitted from the lens circuit LEC. Note that if the photographic lens attached to the camera body is a zoom lens, the lens circuit The LEC includes a zoom encoder linked to the zoom ring, changes information on the focal length and conversion coefficients, and transmits the information to the microcomputer μC.

Each of the input ports P1 to P of the microcomputer μC is pulled up to a "High" level by an internal resistor, and each is connected to the ground level through a separate switch. When any switch is turned on, the corresponding input port becomes the “LO” level, and each switch is turned on.
10 F F can be determined by the microcomputer μC. Each switch will be explained below.

S is a photographing preparation switch that is turned on when the release button is pressed down to the first step, and when this switch is turned on, each operation of photometry, exposure calculation, and automatic focus adjustment is started.

S is a release switch that is turned on when the release button is pressed down to the second step, and when this switch is turned on, an exposure control operation is started.

SMD is a mode changeover switch, and this switch SM
Fantasy mode is selected when D is ON, and normal mode is selected when D is OFF.0 In normal mode, the combination of aperture value AV and shutter speed TV is determined according to the normal program diagram, but in fantasy mode. A combination of aperture value Av and shutter speed TV is determined according to a special program diagram (described later in the explanation of FIG. 5) so that a specific expressive effect can be obtained by driving the lens during exposure.

SAF is an auto/manual switch. When this switch SAF is ON, the autofocus mode is selected to drive the lens to the in-focus position based on the focus detection result, and when the switch SAF is OFF, the autofocus mode is selected based on the focus detection result. Based on this, a manual focus mode is selected in which only in-focus or out-of-focus is displayed and the lens is not driven.

Next, the overall operation of the camera will be explained with reference to the flowchart shown in FIG.

First, in #10, it is determined whether the photographing preparation switch SI is ON. At #10, the shooting preparation switch Sl is turned on.
If not, the determination operation in #10 is repeated and no other actions are performed. If the photographing preparation switch S1 is ON in #10, the operations from #20 onwards are performed.

At #20, lens data unique to the photographing lens is input from the lens circuit LEC. This lens data includes
As mentioned above, the minimum aperture value AV. , maximum aperture value AVM,
Conversion 1 series from focal length f and defocus amount DF to number of delivery pulses ΔP,! & Includes large feed pulse number PM, etc.

At #30, flash data is input from the flash circuit FLC. The flash data includes information regarding the O, N10FF states of the flash light emitting switch FSW, so that the camera body side can know the ON10 FF state of the flash light emitting switch FSW.

In #40, the defocus amount D is sent from the AF control circuit AFC.
F fief! The driving amount ΔP required to drive the focusing lens to the in-focus position is determined according to this information.
and the driving direction and sends it to the AF control circuit AFC.

At #50, a photometry command is given to the photometry circuit LMC to measure the brightness of the photometry areas 81 to S6, and the microcomputer μC receives the data and calculates the brightness Bv of the main subject from the central photometry area 84 to S6. Calculate. The brightness B of this main subject
Used for AE calculation after v&i+.

In #60, it is determined whether the exposure mode is normal mode or fantasy mode by determining the 0N10FF state of the mode switch SMD. If it is determined that the exposure mode is fantasy mode in #60, # 6
Fantasy mode is an exposure mode for obtaining special photographic effects, and its detailed contents will be described later in the explanation of FIGS. 4 and 5. If it is determined in #60 that the mode is normal mode, the process moves to #62 and AE calculation for normal mode is performed. This calculation is well-known, and for example, the aperture value Av and shutter speed are TV
This is done to change the value to 1.1 within a controllable range, and is not directly related to the content of the present invention.
A detailed explanation thereof will be omitted.

The process moves from #61 or #62 to #70, and the ON10FF state of the release switch S2 is determined.

If release switch S2 is not ON in #70, #1
Returning to 0, the same operation is repeated. If the release switch S2 is ON in #70, a release operation is performed in #80, and the process ends.

Here, when fantasy mode is selected, in the release operation of #80, a unique expressive effect is created by driving the focusing lens to defocus while the shutter is open. It is. This effect is due to the effect of increasing the diameter of the circle of confusion (
There are two effects: bokeh effect) and magnification change (image enlargement/reduction) due to change in focal length, and the resulting image changes greatly depending on the contribution ratio of each. If the contribution of the increase in the diameter of the circle of confusion is very large, a depiction similar to that taken with a soft focus lens will be obtained, and if the contribution of the change in image magnification is very large, a depiction similar to that obtained by shooting with an inter-exposure zoom will be obtained. is obtained.

In Fantasy mode, in order to achieve a desirable soft focus effect over a wide brightness range, a sharp, in-focus image is exposed for 1/4 of the total exposure time (i.e. shutter speed), and a sharp image is exposed for the remaining 3/4. By defocusing the image in time, it is possible to obtain an image that has an overall flare and a soft atmosphere, and in which the details of the subject are adequately depicted.

FIG. 6 shows the intensity distribution of a defocused point image; FIG. 6(a) shows an out-of-focus point image intensity distribution, and FIG. 6(b) shows a point image intensity distribution resulting in a preferable soft-focus image. By controlling the exposure of the fantasy mode mentioned above,
The point spread intensity distribution shown in FIG. 4(b) is obtained. This point spread intensity distribution differs from the case of a simple out-of-focus image shown in Figure (a), in that the intensity is concentrated in the central part, which is the nucleus.6 Ratio of exposure time for a focused image The larger the value, the sharper the image, but the shorter the defocus time, the less soft focus effect can be obtained at the same shutter speed. Therefore, the practical range will be narrowed.

FIG. 5 is a program diagram used for the AE calculation in fantasy mode #61. This program diagram is
It is designed to achieve the most desirable degree of soft focus effect determined from the results of subjective evaluation tests over a wide range of brightness as possible. This program diagram will be explained below.

First, let's start with the soft focus effect and shutter speed.
The relationship between aperture values will be explained. The degree of the soft focus effect is evaluated by the size of the spread of the point image due to defocus, that is, the diameter of the circle of confusion. When approximated using geometrical optics, the defocus amount is DF, and the F number of the lens is F.
Then, the diameter δ of the circle of confusion is expressed by the following formula.

δ=DF/F From Kawa's equation, it can be seen that the diameter of the circle of confusion δ is inversely proportional to the F number of the lens. On the other hand, since the shutter speed determines the time it takes to drive the lens, the amount of defocus is determined by the shutter speed. This relationship is
It will look like this: Assuming that the time the shutter is open is 70, the time t for actually driving the lens is 3/4 of the time t0 that the shutter is open, as described above, and is expressed by the following equation.

t=(3/4)to... ■During the time t for driving this lens, the encoder ENC attached to the lens drive shaft generates 0 pulses ΔP shown in Fig. 8(a). The relationship between the number of pulses ΔP and the defocus amount DF differs depending on the lens, and its conversion coefficient is included in the information read into the camera body from the lens circuit LEC. The relationship between the number of pulses ΔP, the conversion coefficient K, and the defocus amount DF is expressed by the following equation.

ΔP=to-DF...■,',D
F = ΔP/K...■Figure 8 (
The number of pulses ΔP shown in a) is expressed as a function f(
t), D F = f(t)/K...
(2) As shown in FIG. 8(a), the number of pulses ΔP can be considered to be proportional to the lens drive time t after a certain period of time has elapsed, and in this case, the function f(t) can be expressed by the following equation.

r(L)=a-t+b...■,'
, D F = (a − t + b) / K
-■Here, a and b are constants.

(2) By substituting the equation into the 0 equation, the following equation is obtained.

δ=(a-t+b)/(K-F) The river ■, that is, the diameter of the two circles of confusion δ is the time during which the shutter is open [. = (
4/3) It is proportional to L and inversely proportional to F number.

When controlling exposure, in order to increase the amount of exposure by 1, the time the shutter is open must change by 1.
Since the F number changes by a factor of 1/fT, on a program diagram that expresses the aperture value AV as a function of the shutter speed TV using the APEX value, the value of the circle of confusion diameter δ is on a straight line with a slope of -2. become equal. This is why, in the program diagram shown in Figure 5, the slope in the section C to d is set to -2, and in this section, the optimal value of the diameter δ of the circle of confusion obtained by subjective evaluation is 1500 μm. Exposure is controlled by a combination of aperture value AV and shutter speed TV. As the exposure value Ev becomes smaller, both the aperture value Ay and the shutter speed Tv become smaller along this line.
When the minimum aperture value of the lens reaches the minimum aperture value AVQ, a smaller aperture value cannot be taken, so only the shutter speed TV is reduced while keeping the aperture value AV at the minimum aperture value AyO. The section age in FIG. 5 corresponds to this control, and in this section, the diameter of the circle of confusion δ takes a value larger than the optimum value. Conversely, when the exposure value Ev increases, it takes a value exceeding the maximum aperture value AVM. Since this is not possible, only the shutter speed Tv is increased while keeping the aperture value AV at the maximum aperture value Av. The section "e" in FIG. 5 corresponds to this control, and in this section, the diameter δ of the circle of confusion becomes a value smaller than the optimum value.

On the other hand, regarding shutter speed TV, the limit of the amount of lens drive during exposure, that is, the amount of drive to the end of either the closest shooting distance side or the infinite shooting distance side (determined by the direction of movement). The shutter speed is controlled so that it does not become less than the limit shutter speed TvL that can be secured. Sections d to e in FIG. 5 correspond to this control. If this control is not performed, the lens will reach the end during exposure and will continue to expose for the rest of the time in a stopped state, resulting in a double image with the sharp image exposed in the initial state. It forms an image and becomes very unsightly. However, even if the shutter speed is less than TV, as in the section azb in Figure 5, if the diameter of the circle of confusion δ is sufficiently large (if the result of subjective evaluation is 3000μI6 or more), a clear two-dimensional (Because it does not form 'A, the diameter of the circle of confusion δ is 30
Shutter speed TV only if it is 00μ- or more
Set to the value for L groove. Note that the shutter speed TV is controlled within the range of the maximum shutter speed TVM and the minimum shutter speed Tvo of the camera.

Next, AE calculation in fantasy mode (#61)
The contents will be explained according to the flowchart shown in FIG. First, in #100, the flash light emitting switch FSW
Determine the ON10 FF state of . When it is determined in #100 that the flash light emission switch FSW is OFF, the process moves to #110 and an exposure value Ev for controlling the camera is calculated from the brightness Bv of the main subject and the film sensitivity value Sv using the following equation.

Ev=Bv+Sv ・”■#100
If it is determined that the flash light emission switch FSW is ON, the process moves to #120, and the exposure value Ev for controlling the camera is calculated using the following equation.

E v= B v1S v11 −
@) That is, during flash emission, in order to control the light amount ratio of flash light and ambient light to 1:1, the exposure value for ambient light is set to a value that is IEv under. This is because the soft focus effect that was originally intended for photography cannot be achieved with flash light alone, so the objective is to obtain a soft focus effect using constant light. Flash light has an extremely short emission time and starts emitting light when the front curtain of the focal plane shutter completes its travel, so it starts emitting light before starting lens drive, and when lens drive starts, It has already stopped emitting light. Therefore, if the flash light occupies a large portion of the exposure amount, the defocused image will not be exposed, making it impossible to obtain a soft focus effect. 1=1
If so, the function of eliminating the defocusing effect of flash light can be used in a more subtle manner to create a softer focus effect on the main subject to which flash light contributes than when shooting with constant light. By reducing the amount of flash light and giving the same soft focus effect as when photographing with constant light to the background area to which flash light does not contribute, it is possible to obtain an expressive effect that clearly separates the main subject from the background and makes it stand out.

Shift from #110 or #120 to #200, auto/
By determining the 0N10FF state of the manual switch SAF, it is determined whether the autofocus mode is set. If the switch SAF is not set to autofocus mode, the lens cannot be driven to obtain a soft focus effect, so #
Move to 1200 and process release vote stop, #20
If it is determined that the switch SAF is set to autofocus mode at 0, the process moves to #210 and the photographing magnification β of the main subject is calculated.

After that, the direction in which the lens is to be driven is determined in steps #300 to #350. First, in #300, the value of the transformation coefficient is 0.7
It is determined whether or not the value is greater than or equal to the value. If ≧0.7, it means that the short focus range of the zoom lens is being used, and the process moves to #330. If it is not ≧0.7 in #300, it is determined in #310 whether the maximum number of pulses P+, I is 3000 or more. If PM≧3000, it means that a macro lens is used, and #33
Transition to 0. #300 and not ≧0.7, and #3
If PM≧3000 is not satisfied in 10, it means that a normal photographic lens is being used, and the process moves to #320. In #320, the shooting magnification β of the main subject is (1/12
> times or more, and if β<1/12, proceed to #340, select the driving direction of the lens (that is, the extending direction) that defocuses in the near direction, and β
If ≧1/12, move to #350 and select a lens drive direction (that is, retraction direction) that defocuses in the far direction. 0 With normal photography lenses, the maximum possible imaging magnification is almost constant. Therefore, by switching the driving direction of the lens at a certain imaging magnification in this way, it is possible to switch the driving direction at a point that is a substantially constant percentage of the lens's drivable range. The value of the photographing magnification β of (1/12) times corresponds to a position further to the extended side than the middle position of the drivable range, and only when the lens is extended beyond this position, the lens is moved in the retracting direction. In all other cases, it is driven in the feeding direction. Thereby, the soft focus effect can be made to look more favorable. In other words, by moving the lens as far as possible, the bokeh will spread outward from the subject, and the background will also be out of focus, giving the entire screen a softer image. It is what it is.

On the other hand, if the short focus range (wide-angle side) of a zoom lens is used, the maximum imaging magnification will be smaller than that of a normal shooting lens, and if a macro lens is used, the maximum imaging magnification will be smaller than that of a normal shooting lens. Since it is larger than the lens, the precondition that the maximum photographic magnification is almost constant is no longer satisfied, and the lens driving direction cannot be appropriately determined by the determination in #320. Therefore, in these cases,
The process moves from #300 or #310 to #330, respectively, and it is determined whether p,>p. Here, P.

is the number of pulses that can be driven in the feeding direction, and PF is the number of pulses that can be driven in the feeding direction. P.N.

PF is a pulse count number P indicating the current position (focus position) of the lens, a pulse number P indicating the maximum driveable amount of the lens, and a minimum pulse count number Po at the time of resetting the lens position counter (this example Then, it can be calculated from P o=O) using the following formula.

PN=PN P...■P,=
P-Po...■PN at #330>
If P, then the number of pulses that can be driven in the feeding direction PN
is larger, so move to #340 and select the driving direction of the lens that defocuses in the near direction (in other words, the extending direction), and on the other hand, if PN≦PF, move to #350. Then, select a lens drive direction (or retraction direction) that defocuses in the far direction. Note that on the short focus side of the zoom lens, the value of the conversion coefficient is relatively large.In the judgment of 5#3°O, if ≧0.7 or more, the short focus range of the zoom lens is used. I judge that.

In addition, the macro lens is a lens with a large maximum extension amount, and the number of pulses P1 indicating the maximum drive amount. Since I is a large value, the determination in #310 is P.

When ≧3000, it is determined that a macro lens is being used.

The process moves from #340 or #350 to #400, and the value of the shutter speed TVL, which is the limit of the lens drive time shown in the program diagram of FIG. 5, is calculated.

When the drive direction determined in #300 to #350 is the feeding direction, the number of movable pulses is calculated using the 0 formula, and when the driving direction is the retracting direction, the 0 formula is used. From the obtained number of movable pulses, a value of shutter speed TvL, which is the limit of lens drive time, is calculated using a conversion table. This conversion table is based on the horizontal axis (number of pulses ΔP) in the function shown in Figure 8(b).
It is made up of a ROM table that stores values on the vertical axis (shutter speed TV) with . In addition, Figure 8 (
The interval number shown in b) is the inverse function of the function shown in Figure 8(a).
It is shown in PEX value.

Next, in #500 to #510, it is determined whether the exposure value Ev calculated in #100 to #120 is within a range that allows exposure control. First, in #500, it is determined whether the exposure value EV is greater than or equal to the sum of the minimum aperture value AVO of the lens and the minimum shutter speed Tvo of the camera (A vo + T vo), and if E v < (A vo + T vo) The process moves to #1100 to issue a low brightness warning.

Next, in #510, the exposure value Ev is the sum of the maximum aperture value AVM of the lens and the maximum shutter speed TVH of the camera (AV
M+TVM) or less is determined, and E v> (A V
M+TVN), #1000 to issue a high-intensity warning.
Move to. In other cases, since the exposure is within the controllable range, the process proceeds to #600.

In #600, the value of the shutter speed TvP corresponding to point C shown in the program diagram is calculated. First, from the minimum aperture value Ay□, use the conversion table to obtain the minimum F number Fo.
Next, calculate the amount of defocus necessary to obtain δ = 1500 Am from the following equation obtained by substituting and transforming Fo as the value of F in the 0 equation and 1500 μ as the value of the diameter of the circle of confusion δ. Find DFP.

DFp=1500XF.

Then, the number of lens drive pulses ΔPP necessary to obtain this defocus amount D Fp is determined from the following equation, which is a modification of the equation 0.

ΔPp=DFPXK The shutter speed TvP corresponding to point C is calculated from the determined number of lens drive pulses ΔPP using the function shown in FIG. 8(b) (the same ROM table used in #400).

Next, #700~#78o, #100~#120″
Based on the exposure value EV calculated by C', a combination of aperture value AV and shutter speed TV for controlling the camera is determined according to the program diagram shown in FIG.

First, in #700, it is determined whether TvP≧TvL. If T vp < T vt in #700, #71
0, 'rvp='rvL' and the process moves to #72o. Also, if #700''C'TVP≧TvL, the process directly proceeds to #720.This is because the above-mentioned method is used when the diameter of the circle of confusion δ does not exceed 1500 μm even if the lens is driven to the limit. This is a process to prevent double images from being formed. In #720, Ev≦(Avo+Tvp
) or not. #720'cEv≦(A vo+
T vp), the aperture value AV and shutter speed TV are calculated using the following formula in #73o, and the processing to move to #900 is performed using the section ag in the program diagram in Figure 5.
This corresponds to the control of e.

Av: Av.

T v = E y A y If EV≦(A vo + T vp) in #720, the process moves to #740, and the aperture value AV and shutter speed TV are calculated using the following equations.

Av=2 (Ev Tvp) Av.

T y = E v A v This process is carried out in the section C~ in the program diagram of FIG.
This process corresponds to the control of d and calculates a combination of aperture value AV and shutter speed TV that results in a circle of confusion diameter δ of 1500 μm. In #750, it is determined whether the shutter speed TV calculated in #740 is less than the shutter speed TvL that is the limit of the lens drive time. T at #750
If y< T VL, recalculate the aperture value AV and shutter speed TV in #760 using the following formula, and
to move to.

This process is carried out in sections d to e in the program diagram of FIG.
corresponds to the control of

TV=TVL AV=EV-TV If Tv≧'rvt in #750, move to #77o and check whether the aperture value AV calculated in #740 or #760 is larger than the maximum aperture value AVM or not. Determine.

If A y > A VM in #770, recalculate the aperture value AV and shutter speed TV using the following formula and return to #800.
to move to. This process corresponds to the control of section ezf in the program diagram of FIG.

A y :A VM Tv=Ev-Av If AV≦AVM in #770, the process moves to #800, and the 0N10 FF state of the flash light emission switch FSW is determined. At #800, the flash light switch FSW is O.
If it is FF, the process directly proceeds to #900, and if it is ON, the light control level is set so that the flash exposure amount is 1Ev under.

As a result, the main subject is properly exposed in conjunction with the exposure amount due to the constant light determined in #120.

In #90o to #930, it is determined whether a special photographic effect using the fantasy mode can be obtained.

First, in #900, the diameter δ of the circle of confusion is calculated from the aperture value AV and shutter speed TV determined in steps #700 to 780. To calculate the value of the diameter of the circle of confusion δ, first use the formula 0 to calculate the defocus JiDF=f(1/K). The shutter speed L0 corresponding to the lens driving time t is used as an address to obtain the number of pulses ΔP, and the F number is obtained from the ROM table that stores the F number.

The value δ=DF/F is calculated from the calculated defocus amount DF and the F number using the formula 0.

In #910, it is determined whether the diameter δ of the circle of confusion is less than 500 μm. Under conditions where the diameter of the circle of confusion δ is less than 500 μm, it is determined that the soft focus effect cannot be obtained, and #1
Proceed to 000, if δ<500μm at #910,
In #920, it is determined whether the shutter speed TV is less than the shutter speed TVL, which is the limit of the lens driving time. If TV≧TVL in #920, the lens does not reach the end while driving the lens during exposure, and this is a condition for obtaining special photographic effects, so the process returns directly.

If TV<TV in #920, δ≧30 in #930
It is determined whether or not it is 00 μm-. #930 and 623
If it is 0008M, the condition is such that a special photographic effect can be obtained even if T y < T V L, so the process returns as is. If δ<3000μ- in #930, it is determined that an undesirable double image is formed, and the process proceeds to #1100.

At #1100, as shown in FIG. 9(a), “
"Lo" is displayed. This display can prompt the photographer to increase the brightness of the subject in some way, and for example, it is possible to obtain a photographic effect by illuminating the subject.

At #1000, the characters "Hl" are displayed as shown in FIG. 9(b) to warn that the brightness is too high and the special photographic effect of the fantasy mode cannot be sufficiently obtained. This display can prompt the photographer to lower the brightness of the subject in some way, and for example, it is possible to obtain a photographic effect by attaching a neutral density filter.

#1200 avoids taking photos that do not have the special shooting effects of fantasy mode when the warning display of #1000 or #1100 is displayed or when it is determined that the AF mode is not available in #200. Therefore, a release prohibition process is performed, specifically, a release prohibition flag is set, and as a result, release in fantasy mode is prohibited in the process of #80 (see FIG. 3).

[Effects of the Invention] In the present invention, in a camera capable of driving the lens during exposure, the aperture value and shutter speed are determined so that the diameter of the circle of confusion becomes a substantially constant value, which is subjectively preferable. A soft focus effect can be obtained over a wide brightness range.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of the present invention, FIG. 2 is a block circuit diagram of a camera as an embodiment of the present invention, FIG. 3 is a flowchart for explaining the overall operation of the same, and FIG. 4 is a flowchart for explaining the contents of AE calculation in fantasy mode as above, Fig. 5 is a program diagram showing an AE program in fantasy mode as above, and Fig. 6 (&) is a point spread intensity distribution of an out-of-focus image. 6(b) is a diagram showing the point spread intensity distribution of a soft focus image, FIG. 7 is a diagram showing the photometry area of the photometry circuit used in the above camera, and FIGS. 8(a) and (b). ) is a diagram showing the relationship between the number of pulses and the shutter speed due to lens driving during exposure, and FIGS. 9(a) and 9(b) are explanatory diagrams illustrating warning displays used in the same camera. 1 is a photographing lens, 1a is a focusing lens, 2 is a lens drive means, 3 is a photometry means, 4 is an exposure calculation means, 5 is an aperture control means, and 6 is a shutter speed control means.

Claims (6)

[Claims] (1) In a camera that is equipped with a lens drive means that drives a part of the photographic lens during exposure, and obtains special photographic effects by driving the lens during exposure, there is a light metering means that measures the brightness of the subject, and a camera that measures the brightness of the subject and an exposure calculation means for determining an aperture value and a shutter speed; an aperture control means for obtaining the aperture value determined by the exposure calculation means; and a shutter speed control means for obtaining the shutter speed determined by the exposure calculation means. A camera capable of driving a lens during exposure, characterized in that the exposure calculation means is means for determining an aperture value and a shutter speed so that a diameter of a circle of confusion is a substantially constant value. (2) A camera capable of driving a lens during exposure according to claim 1, wherein the exposure calculation means is a means for determining an aperture value and a shutter speed so that a diameter of a circle of confusion is about 1500 μm. (3) Claim 1, characterized in that the exposure calculation means is means for decreasing the shutter speed as the luminance increases.
Or a camera capable of driving a lens during exposure as described in 2. (4) The exposure calculation means is a means for changing the aperture value expressed by the apex value and the shutter speed at a ratio of 2:-1 as the exposure value expressed by the apex value increases. A camera that can drive the lens between exposures. (5) The exposure calculation means is characterized in that when the determined shutter speed is slower than the threshold shutter speed at which the lens reaches its end, the exposure calculation means selects the threshold shutter speed at which the lens reaches its end. 5. A camera capable of driving a lens during exposure as claimed in claim 4. (6) The exposure calculation means is capable of calculating an aperture value that exceeds the control limit of the aperture control means and/or shutter speed control means.
2. A camera capable of driving a lens during exposure as claimed in claim 1, further comprising means for selecting a control limit aperture value and/or shutter speed when the shutter speed is selected.