GB2241073A

GB2241073A - Camera with mid-exposure zooming function

Info

Publication number: GB2241073A
Application number: GB9103199A
Authority: GB
Inventors: Shinsuke Kohmoto; Tomoaki Itabashi; Isao Soshi; Tatsuhide Takebayashi
Original assignee: Asahi Kogaku Kogyo Co Ltd
Current assignee: Pentax Corp
Priority date: 1990-02-14
Filing date: 1991-02-14
Publication date: 1991-08-21
Anticipated expiration: 2011-02-14
Also published as: DE4104558A1; GB2241073B; FR2658320B1; FR2658320A1; GB9103199D0; DE4104558C2

Abstract

A camera having a mid-exposure zooming function, including a zoom motor driving a zoom lens, a trigger switch initiating mid-exposure zooming EXZ, and mid-exposure zooming execution means for initiating the driving of said zoom motor based on the operation of the trigger switch for initiating exposure. The camera is preferably an SLR. A start switch 31 and a mode selection switch 33 are shown. <IMAGE>

Description

-I- CAMERA WITH MID-EXPOSURE ZOOMING FUNCTION The present invention

relates to a camera with a powered zoom lens, and more particularily to a camera with mid-exposure zooming function, i.e., a camera having a zooming function which is operable during exposures.

Mid-exposure zooming is a photographing technique whereby focal length is intentionally changed during the period of an exposure so as to provide the particular effect of representing a sense of movement by utilizing the mechanism of variable focal length which is characteristic of the zoom lens. In general, the pictures taken by the mid-exposure zooming have a flow of an image due to the focal lengt4 change during exposure.

This mid-exposure zooming operation is carried out during the time of exposure, and so its results depend on the shutter-releasing timing, a preset shutter speed, a manual adjustment of the zooming speed, and so on.

Thus, the operation relies on the "skilled-technique" or the "intuition") of the user.

In a camera having a powered zoom lens, i.e., a zoom lens using a driving power for the zooming operation, such a mid-exposure zooming operation may be carried out relatively with ease, but the camera is not designed to perform the exposure and the zooming operations in coordination, and therefore a skilled technique is needed on the part of the user for releasing the shutter while simultaneously manipulating the powered zoom switch so it turns ON. Consequently, using this type of camera is slightly more convenient than using the type of camera having a manual mode zooming function.

4 2 It is therefore an object of the present invention to provide a camera adapted to carry out mid-exposure -zooming automatically and reliably through a simple manipulation.

According to one aspect of the present invention there is provided a camera having a mid-exposure zooming function comprising:

zoom motor for driving a zoom lens; trigger switch for starting mid-exposure zooming; mid-exposure zooming execution means for starting the driving of said zoom motor based on the operation of said trigger switch for starting exposure.

This arrangement permits the user to carry out the midexposure zooming operation automatically and with reliable results, as it is not necessary to rely on the user's technique.

Said means for executing the mid-exposure zooming operation consists of the zooming starting means and the exposure starting means.

Preferably, there is provided a means for detecting sufficient condition for enabling the exposure starting means to start exposure synchronously with the operation of the zooming starting means. This arrangement permits the user to carr y out the mid-exposure zooming operation manually with ease, and also allows the user to initiate the exposure operation once a zooming movement has become stable, for maximum effect. The mid-exposure zooming execution means comprises: zooming starting means; exposure starting means; counting means for counting down the exposure time after the actuation of said zooming starting means; means for reading a shutter speed; and means for stopping the rotation of the zoom motor upon the count-down value in said counting means' having reached a predetermined ratio in a total exposure time, thereby permitting the user to carry out the midexposure zooming operation manually with ease and to stop the zooming operation automatically prior to completion of the exposure.

Preferably, the means for executing the mid-exposure zooming operation comprises: detection means for focal 1 Ar A -3length; focal length memory means for storing focal length data both at the beginning and the end of the zooming operation, respectively; means for reading the shutter speed; and motor speed control means for controlling the thereby permitting the user to carry out the mid-exposure zooming operation manually with ease, and to set the zooming speed appropriately according to the the result of the comparison between the focal length and the shutter speed so that an image with a smooth and unvarying density may be formed.

In another preferred embodiment of the present invention, the means for executing the mid-exposure zooming operation further comprise focal length detection means for detecting variation in the magnitude of the focal length, comparison means for comparing focal length variation which is detected with a variation ratio of the focal length, motor speed control means for controlling the rotation speed of the zoom motor according to comparison results issued from this comparison means, thereby permitting the user to carry out the mid-exposure zooming operation with ease to keep variation in focal length at a constant while performing a zooming operation so that an image with a smooth density may be obtained.

In still another preferred embodiment of the present invention, the means for executing the mid-exposure zooming operation further comprise focal length memory means for storing focal length data, and motor control means for stopping the zoom motor upon its reaching a particular focal length, in order to stop the zooming operation as stored in this memory means and thereby permit the user to carry out the mid-exposure zooming operation manually with ease and to terminate the zooming operation at any focal length which has been set to end the zooming operation after use has confirmed the focal length by, for example, looking in through the finder. This also permits the user to Imagine the photograph to be finally formed before it has actually driving speed of the zoom motor 1A 4 been taken.

Furthermore, in accordance with one aspect of the present invention, the means for executing the mid-exposure zooming operation further comprises shutter speed reading-in means for reading in the shutter speed, and zooming starting limit means for actuating the midexposure zooming operation only when the shutter speed is slower than a reference shutter speed which has been preset beforehand, thereby permitting the user to carry out the raid-exposure zooming operation manually with ease and limit the mid-exposure zooming operation under the slit exposure. This also serves to avoid the problem that the resultant image may contain irregular exposures.

In addition, if the camera of the invention comprises the mid-exposure zooming mode wherein the zooming operation is actuated during exposure and control means for varying the zooming speed in response to the variation in the F value of the diaphragm caused by the zooming operation, then an uneven exposure in the resultant image will be eliminated in case where the mid-exposure zooming operation is carried out by means of the zoom lens which varies its F value due to zooming.

According to another aspect of the present invention there is provided a camera having a mid-exposure zooming function comprising:

zoom motor for driving a zoom lens; trigger switch for starting mid-exposure zooming; zooming starting means for starting the driving of said zoom motor based on the operation of said trigger switch; exposure starting means for starting exposure based on the actuation of said zooming starting means; and counting means for counting the exposure time synchronously with the operation of said zooming starting means, said exposure starting means starting exposure when the counting means count predetermined time.

A Preferably, said predetermined time is a time period with which the zooming speed of said zoom lens becomes constant.

Conveniently, said predetermined time is set at 1110 of the whole exposure time.

The camera may further comprise a start button by which the zooming start means is operated.

a zoom motor for driving a zoom lens; means for reading-in a preset shutter speed; mid-exposure zooming execution means for driving said zoom motor, and for starting exposure; counting means for counting the exposure time synchronously with the actuation of said mid-exposure zooming exposure execution means; and zooming termination means for stopping the driving of said zoom motor when a value counted by said counting means reaches the predetermined rate of the whole exposure time corresponding to the shutter speed read in said shutter speed reading in means.

The means for reading in a preset shutter speed may further comprise a shutter dial to set a shutter speed which is to be read in the means for reading in a preset shutter speed.

Preferably, said predetermined rate of the whole exposure time is 80% of the whole exposure time.

According to a still further aspect of the present invention there is provided a camera having a mid-exposure zooming function comprising:

a zoom motor for driving a zoom lens; focal length detection means for detecting the focal length of said zoom lens; mid-exposure zooming execution means for driving said zoom motor, and for starting exposure; 4 6 focal length memory means for memorizing focal length upon starting of zooming and focal length upon completion of zooming; means for reading in a preset shutter speed; and motor speed controlling means for controlling the driving speed of said zoom motor on the basis of f ocal length data from said f ocal length memory meafis and shutter speed data from said shutter speed reading-in means.

conveniently, said zoom lens includes a memory switch, and said focal length memory means operate based on the operation of the memory switch.

The means f or reading in a preset shutter speed may further comprise a shutter dial to set the shutter speed which is to be read in the means f or reading in a preset shutter speed.

According to yet another aspect of the present invention there is provided a camera having a mid-exposure zooming function comprising:

a zoom motor for driving a zoom lens; mid-exposure zooming execution means f or driving said zoom motor, and for initiating exposure; f ocal length variation means f or detecting the amount of variation of focal length performed by said zoom lens; comparison means for comparing variation detection means with the predetermined variation rate of focal length; and motor speed control means for controlling the rotation speed of said zoom motor based on the result of comparison performed by said comparison means so as to maintain the variation rate of focal length upon zooming at constant value.

Preferably, said motor speed control means increases rotation of the zoom motor when the f ocal length variation detected by the focal length variation detection means is larger than the predetermined variation rate of f ocal length, and said motor speed control means decreases rotation of the zoom motor 1 ' 7 variation detection means is -smaller than the predetermined variation rate of focal length.

a zoom motor for driving a zoom lens; mid-exposure zooming execution means for driving said zoom motor, and for starting exposure; memory means for memorizing the focal length upon completion of zooming; and motor controlling means for stopping said zoom motor when the focal length reaches said focal length upon completion of zooming as memorized in said focal length memory means during mid-exposure zooming.

The zoom lens may include a memory switch, and said focal length memory means for memorizing the focal length upon completion of zooming operates based on the operation of said memory switch.

a zoom motor for driving a zoom lens means for reading in a preset shutter speed; mid-exposure zooming execution means for driving said zoom motor, and for staring exposure; and zooming starting limiting means for allowing operation of said mid- exposure zooming staring means only when the shutter speed is slower than the predetermined standard shutter speed.

C onveniently, said predetermined standard shutter speed is a synchronous speed of X contact.

According to another aspect of the present invention there is provided a camera including a mid-exposure zooming function, said camera having a powered zoom function, comprising:

1k 8 a mid-exposure mode for zooming during the exposure operation; and controlling means for varying the zooming speed during exposure in accordance with the variation of the diaphragm effected by zooming.

Preferably, said zooming speed is set such that it becomes faster when the diaphragm is light, and slower when the diaphragm is dark.

The present disclosure relates to subject matter contained in Japanese patent applications No. 02-33003, 0233004, 02-33005, 02-33006, 02-33007, 02-33008 and 02-33015 (all filed on February 14, 1990) which are expressly incorporated herein by reference in its entirety.

An example of the present invention will now be described hereinbelow, with reference to one embodiment shown in the accompanying drawings, in which:

Fig. 1 is a block diagram showing a control circuit of the camera with one embodiment of the invention; Fig. 2 is a lateral view showing the general appearance 4, -9of the camera; Fig. 3 is plan view of Fig. 2; Fig. 4 is a schematic view showing the actuating mechanism of the powered zoom lens; Fig. 5 is front cross-sectional view showing a portion of the powered zoom lens on a partially enlarged scale; Fig. 6 is an enlarged cross-sectional view showing the construction of the Pz mode switch; Fig. 7 is an enlarged view of the code plate into which zooming positions are read; Fig. 8 is an enlarged view showing the control input substrate; Fig. 9-11 are flow charts showing how the first embodiment operates; Fig. 12 is a f low chart showing a second embodiment of the invention; Fig. 13 is a block diagram showing a control circuit for a camera in a third embodiment of the invention; Fig. 14 is a flow chart showing how the third embodiment operates; Fig. 15 is a block diagram showing a control circuit in a fourth embodiment of the invention; Fig. 16-18 are flow charts showing how the fourth embodiment operates; Fig. 19 is a block diagram showing a control circuit in a fifth embodiment of the invention; Fig. 20-22 are flow charts showing how the fifth embodiment operates; Fig. 23 is a block diagram showing a control circuit in a sixth embodiment of the invention; Fig. 24-25 are flow charts showing how the sixth embodiment operates; Fig. 26-28 are flow charts showing how a seventh embodiment of the invention operates; Fig. 29 is a view showing the outline of the power zoom -10lens and its control block In the eighth embodiment of the invention; Fig. 30 is a graph showing the relationship between the rotating speed R of the zoom motor and the focal length F.

Fig. 31 is a graph showing the relationship between the focal length scale width and a focal length in the eighth embodiment; Fig. 32 is a focal length scale which corresponds with that In the Fig.31 graph; Fig. 33 is a graph showing the relationship between the focal length f and the open F value in a traditional zoom lens; and Fig. 34 is a view showing a focal length scale with the magnitude of variation of the focal length relative to the rotation angle of the zoom operating ring.

Figs. 2 and 3 show a camera 10 in which the present invention is embodied.

The camera (single lens reflex camera) comprises an automatic focusing device and an automatic exposure device in addition to a power zoom lens.

A body 12 of the camer - a 10 is provided at its f ront surface with a zoom lens 13 and a grip portion 14. Provided on the upper surface of the camera body are a shutter release switch (button) 15, and a mode selection switch (button) 16 for switching the camera photographing mode. The shutter release switch 15 is connected to a light measuring switch SWS so that when the release switch 15 is depressed half-way (first step), the light measuring switch SWs is made ON.

As shown in Fig. 4, the zoom lens 13 comprises two sets of lens groups Ll and L2. The first and the second lens groups Ll and L2 have a plurality of roller pins 70 and 71 secured to and projected radially outwards from the outer 4 -11circumference thereof, these roller pins 70 and 71 engaging in cam grooves 72 and 73 formed in a cam ring 19. At least one roller pin of respective roller pins 70 and 71 engages a linear guide groove formed in a stationary lens barrel 17.

An annular gear 60 is fixed in position around the outer circumferential surface of the cam ring 19, and a pinion 61 of a zoom motor 4 engages the gear 60. Thus, the cam ring 19 is driven to rotate by means of the zoom motor 4 to move the f irst and the second lens groups Ll and L2 in the optical axis direction thereof, thereby providing a zooming ef fect. A decoder 67 is provided on the outer circumferential surface of the cam ring 19 for detecting the position of the cam ring 19 and determining the focal length f. This decoder 67 consists of a code plate 22 (Fig. 7) and a code plate brush 28.

Signals which are read out by the decoder 67 are output to a lens CPU 66. The lens CPU 66 determines a focal length f and its corresponding fullopen F No.(value) (minimum F number) from the output of the decoder 67, and then these data are output to camera body 12. There is zoom-manipulating ring 75 operation.

An outer stationary lens barrel 17 comprises a wide-angle switch (button) 29, a telescoping switch (button) 30, a start switch (button) (trigger switch) 31 and a Pz (power zoom) mode selection switch (button) 33 ( Figs. 2 and 3).

The wide-angle switch 29 and the telescoping switch 30 in Fig. 5 have springs which make them flexible and comprise conductive contact strips 29a and 30a at the position where they lie opposite to a control input substrate 35 (Fig. 8). Thus, when the wide-angle switch 29 is depressed, the conductive contact strip 29a come into electrical contact with the control input substrate 35 to turn it ON, whereas the conductive contact strip 30a comes into a control section 1 of the also shown in Fig. 4 a for use in a manual zooming i -12electrical contact with the control input substrate 35 when the telescoping switch 30 is depressed.

The Pz mode selection switch 33 is adapted to switch a photographing operation between the Pz ( power zoom) mode and the Exz (exposure zoom) mode, and the switch 33 can be actuated by moving the Pz mode switch 33 in the forward and rearward directions to cause a code plate brush 40 to come into contact with ' the control substrate 35 for selecting an operational mode.

Now, the control circuit of the camera 10 in the f irst embodiment of the invention will be described with reference to Fig. 1.

Connected with the input of the control section 1 are the release switch 15, the wide-angle switch 29, the telescoping switch 30, the Pz mode selection switch 33 and the mode selection switch 16. Connected with the output of the control section 1 is a solenoid 5, which actuates shutter, and the motor 4. The control section 1 comDrises the Pz mode selection means 6, mode selection means 7, zooming starting means 8, exposure starting means 9 and count means 14.

The mode selection means 6 is adapted to switch the operating mode between the Pz mode and the ExZ mode In response to an input signal from the Pz mode selection switch 33.

The mode selection means 7 is adapted to switch the operating mode into the self-timer mode, etc., in response to the input signal from the mode switch 16.

The zooming starting means 8 is adapted to initiate a zooming operation by outputting a drive signal to the motor 4 in response to an input signal from either the wide-angle switch 29 of the telescoping switch 30.

The count means 14 initiate its count-down action in synchronization with the starting of the zooming operation by the zooming starting means 8.

The exposure starting means 9 Initiates an exposure i 13 operation by outputting a signal to the solenoid 5 after a passage of preset time after the start-up of the count-down operation by the count means 14. The above mentioned predetermined time means the time during which the zooming speed becomes constant. The predetermined time could be set at 1110 of the whole exposure time.

Figs. 9-12 show the operation of the camera having the construction as above-described.

In step S1, it is judged whether the light measuring switch SWS is ON or not. If the light measuring switch is not turned ON, the step S1 is repeated. The process advances to step S2 when the switch is turned ON.

In step S2, it is judged whether the mid-exposure zooming operation is about to be taken, and the process advances to step S3 if the midexposure zooming is about to be taken, or the process advances to step S4 if the mid-exposure zooming operation is not to be taken.

During this period, a photographing composition is determined, and the shutter speed is preset by manipulation of the shutter dial.

In step S3, it is judged whether the Tv value (shutter speed) is slower or faster then the synchronous speed of the X contact (synchronous speed of the strobe), and the process is repeated if the shutter speed is faster than the synchronous speed of the X contact, or the process is advanced further to step SS to read in the Tv value B if the speed is slower than the synchronous speed of the X contact.

At this point, the user may move the zoom lens 13 to shift its focal length in a direction which is opposed to the direction of intended zooming during the nid-exposure mode. Then, the Pz mode selection switch 33 can be manipulated to set it to the Exz mode.

In step S6, it is judged.whether the wide-angle switch 29 is ON or not. The process is advanced to step S7, if the wide-angle switch 29 is turned ON for driving the zoom motor 4 to by-pass the process into step S3. The process is advanced to step S8 if the wide-angle switch 29 is not turned ON.

1 In step S8, it is judged whether the telescoping switch 30 is ON or not, and the process is advanced to step S7 if the switch 30 is turned ON. The process advances to step S9 if the switch is not turned ON.

In step S9, a focal length f 1 i read in, and it is judged whether the start switch 31 is turned ON in step S32. As a result, the process advances to step S10 if the switch is turned ON, or the process is returned to step S6 if the switch 31 is not turned ON.

In step S10, It is judged whether the wide-angle switch 29 is ON or not, and the process jumps to step S12 if the switch 29 is turned ON, or the process advances to step S11 if the switch is not turned ON.

In step S11, it is judged whether the telescoping switch 30 is ON or not, and the process advances to step S12 if the switch is turned ON, or the process returns back to step S32 if the switch is not turned ON.

In step S12, the zooming direction of the lens is read in, and then in step S13 the zoom motor is actuated to advance the process to step S14.

In step S14, the count means 14 initiates its count-down operation of the Td value (value counted down from the starting of the zooming operation) to advance the process to step S15.

In step S15, it is judged whether or not the Td value equals the value A ( a preset value used to initiate the exposure operation at a selected count-down value after the zooming starting), and the process advances to step S16 if a preset value is reached, or returns back to step S14 if the preset value is not reached.

In step S16, a release signal is emitted by exposure starting means 9, and it is judged whether a switch 2CSW (which is adapted to be turned ON once the second blind of the focal plane shutter has finished its movement) is turned ON.

As a result, the process advances to step S18 if the i switch is turned ON, then the nroces in order to stop the zoom motor 4, goes to Return(in flow-chart). If the switch is not turned ON, step S17 is repeated.

From step S2, the process can advance via step S4 to step S20, if the wide-angle switch 29 is turned ON to drive the zoom motor 4, or the process advances to step S21 if the switch 29 is not turned ON.

In step S21, it is judged whether the telescoping switch 30 is turned ON, and the process advances to step S22 if the switch is not turned ON or to step S20 if the switch 30 is turned ON.

In step S22, it is judged whether or not the release switch is ON, and the process returns back to step S4 if the switch is not turned ON. If the switch is turned ON, the process advances to step S23 to actuate the exposure starting means 9 to emit a release signal, thereby advancing the process to step S24.

In step S24, it is judged whether or not the switch 2CSW is ON; the process is repeated if the switch is not turned ON, and the process goes to Return if the switch is turned ON.

Next, there is a second embodiment of the present invention wherein a process occurring just after step S14 in Fig. 11 is modified; this will be described with reference to Fig.12. In the first embodiment, after the zooming operation is initiated by turning ON the start switch 31, the Td value is counted down to determine the starting timing of the exposure. The exposure operation is initiated in this second embodiment by detecting a time when the magnitude A f in the focal length variation reaches a preset value.

r In step S261 focal length is monitored after the actuation of the zoom motor 4 (step S 13).

In step S27, it is judged whether A f=A and the process returns back to step S26 if the relationship A f=A is not present, and the process advances to step S28 if A f =A is present to actuate the exposure starting means 9 to generate the release signal. It is further judged whether the switch 2CSW is turned ON or not (step S29).

The process is repeated at step S29, and if the switch is turned ON the process deenergizes the zoom motor 4 (step S30) for Return.

Thus, the mid-exposure zooming may be carried out automatically simply by turning ON the start switch 31 without relying on the skilled-technique of the user in accordance with the first and the second embodiments. Furthermore, an exposure operation can be initiated in a predetermined period of time after the starting of the zooming operation, and consequently the exposure operation may be initiated after the zooming operation becomes stable, thereby eliminating the inconvenience of things such as camera shakes, and unstable zooming speed. Thus, the disadvantage of having the image of the object photographed in an excessively clear way before the zooming operation begins is eliminated.

The control circuit of the camera 10 will be described hereinbelow for the third embodiment of the invention, with reference to Fig. 13. Components which are similar to those in the first and the second embodiments will be indicated with similar symbols in this embodiment.

The control section 1 comprises shutter speed read-in means 50 and zooming-termination means 24 in addition to various means as described in the second and the third embodiments, and having a shutter dial 51 connected therewith.

The shutter read-in means 50 is adapted to read in the shutter speed as established by the shutter dial. The zooming termination means 24 acts to stop the zoom motor 4 1:

1 k f rom driving when the count-down value by the count means 14 reaches a preset level relative to the shutter speed as read in by the shutter speed read-in means 50.

The third embodiment is similar to the first embodiment in terms of many aspects of operation, but they are different in the process occurring after step S16 in Fig.

This process will be indicated in Fig. 14.

In step S14, the counting means 14 initiates the countdown of the Td value.

In step S15, it is judged whether the Td value equals the value A; the process is repeated if they are not equal, and the process advances to step S16 if they are equal to each other. In step S16, the release signal is generated by means of the exposure

starting means 9 to advance the process to step S49.

In the step S49, the count means 14 counts down the exposure time after the exposure starting means 9 has initiated its exposure operation.

In step S50, the shutter speed read-in means 50 compares a value which has been calculated as 80% of the shutter speed as read in by the shutter speed read-in means 50 and the exposure time T. As a result, the process is repeated in step S49 if the exposure time T is shorter than a calculated value. The process advances to step S51 if the exposure time T is longer than or equal to a calculated value.

In step S51, the zoom motor 4 is stopped in accordance with a signal from the zoom termination means 24 and the process advances to step S59 af ter the end of the zooming operation.

In step S59, it is judged whether the switch 2CSW is ON or not. As a result, the process repeats step S59 if the switch is not turned ON, and the process goes to Return if the switch is turned ON.

Thus, the mid-exposure zooming operation may be carried out automatically without relying on a skilled-technique on the part of the user. Moreover, the zooming operation may be terminated automatically before the exposure operation is completed. In this way, anyone can easily use the technique of photographing the object immediately after the completion of the zooming operation.

In the above embodiment, the shutter speed read-in means 50 compares the eiposure time T with 80% of the shutter speed as read in by the shutter speed read-in means 50; such a percentage of the calculated value relative to the shutter speed may be set arbitrarily.

The control circuit of the camera 10 will be described with reference to the fourth embodiment of the invention, with reference to Fig. 15.

The portions which the fourth embodiment has in common with the third embodiment are indicated with similar symbols.

The control section 1 comprises a code plate brush 28 to be contacted by a code plate 22, a memory switch 32, a start switch 31, all components being connected therewith, at the input side, in addition to various switches and means as described in the third embodiment. The control section 1 further comprises focal length memory means 45, exposure control means 46, motor speed control means 47, and focal length detection means 49.

The focal length memory means 45 is adapted to memorize the focal length fl when a zooming operation is terminated at a position where the zooming operation is to be ended, and the focal length f2 at the position where the zooming operation is initiated.

The exposure control means 46 control the exposure in response to signals from the shutter speed read-in means 50.

The motor speed control means 47 calculates a proper rotating speed of the zoom motor 4 in response to the shutter speed TV which is input into the shutter speed read-in means 50 to control the zoom motor 4 such that the 4.' -19zoom motor may be rotated at this speed as calculated.

The focal length detection means 49 receives signals as read in by the decoder 67 via a lens CPU 66 to thereby detect the focal length at the time of the zooming operation.

The zooming starting means 8 in the same embodiment actuates the zoom motor 4 to output drive signals via the motor speed control means 47 in response to input signals from the wide-angle switch 29 or the telescoping switch 30, thereby initiating the zooming operation.

The present embodiment has many aspects which are identical with those in the first embodiment, except for a process to be followed after step S9. This difference is shown in Figs.16-18.

The controlling sequences which are the same as those in the first embodiment are executed up to step S8. If the telescoping switch 30 is not turned ON in step S8, the process advances to step S94.

The memory switch 32 is turned ON in order to memorize the focal length fl when the zooming operation is terminated by the zooming operation and had its composition determined via step S7. Then, it is judged whether the memory switch 32 is ON or not in the step S94. The process is repeated if the memory switch 32 is not turned ON, and the process advances to step S69 if the memory switch 32 is turned ON.

In step S69, the focal length fl for terminating its zooming operation is read in the focal length memory means 45 to judge whether the wide-angle switch 29 is turned ON (step S70).

The process advances to step S72 to drive the zoom motor 4 if the wideangle switch 29 is turned ON, thereby initiating the zooming operation. The process advances to step S71 if the switch is not turned ON.

In step S71, it is judged whether the telescoping switch 30 is turned ON, and the process advances to step S72 to drive the zoom motor 4 if the switch is turned ON, 1 -20thereby initiating the zooming operation. The process advances to step S73 if the switch is not turned ON.

The memory switch 32 is turned ON so that the memory means 45 can memorize the focal length at the starting time when the composition of an image is determined by zooming operation. Then, in step S73, the memory switch 32 is judged whether it is ON or not. If it is not turned ON, the step S70 is repeated, or if it is turned ON, the process advances to step S74.

In step S74, the zooming lens 13 has its position read in the focal length memory means 45 as a focal length f2 at the starting of the zooming operation, and the process advances to step S75. - In step S75, the zooming termination focal length fl as read in step S69 is compared withthe zooming starting time focal length f2. As a result, the process is repeated if a relationship fl=f2 exists, and the process advances to step S76 if a relationship fl=f2 is not established.

In step S76, the zoom motor 4 is caused to rotate in order to drive the zooming lens S73 into a zooming termination focal length fl to advance into step S77.

In step S77, the motor speed control means 47 calculates a proper rotating speed of the zoom motor 4. The proper rotation speed is calculated in the following way:

If it is assumed that the focal length at the termination of the zooming operation is set as fl [mm], and the focal length at the starting of the zooming operation is f2 [mm], then the magnitude of variation A f [mm] can be obtained from the following equation:

A f=f2-fl If the shutter speed is t [sec] and the variation magnitude in the focal length per one revolution of the zoom motor 4 is A f (1), then the zoom motor 4 is rotated 1 with the amount of:

A f / A f(l) Consequently, the rotating speed of the zoom motor 4 to complete this rotation is t [sec], and the following relationship exists:

(A f/A f(l))/t=(f2-fl)/A f(l). t [number of rotation/sec).

Then, the mode switch 33 is operated to switch the operating mode into the Exz mode.

In step S78, It is judged whether the start switch 31 is ON or if the switch is not ON, and the process is repeated in step S78, and the process advances to step S79 if the switch is turned ON.

In step S79, it is determined whether the release switch is ON or not, and the process is repeatedin step S78 if the release switch is not turned ON, and the exposure starting means 9 is actuated to generate the release signal if the switch is turned ON (step S86).

In step S87, it is judged whether A f>O, The process advances to step S89 if it is not true in order to drive the zoom motor 4 to a wide-angle side. The process advances to step S88 if A fA to drive the zoom motor 4 to the telescoping side.

In step S90, the current focal length f is monitored to judge whether the focal length f2 for the starting of the zooming operation is equal to the focal length f selected as the target.

As a result, the process is returned to step S87 if f:;t f 2, and the process advances to step S91 if f=f2 to terminate the zoom motor 4 by means of the zooming termination means 24.

k 1 1 In step S92, it is judged whether the switch 2CSW is ON or not; the process is repeated in step S92 if the switch is not turned ON, and the process goes to Return if the switch is turned ON.

Consequently, the mid-exposure zooming operation may be automatically carried out without relying on a skilled technique on the part of the user, and besides the zooming speed may be properly set from comparison results of the focal length with the shutter speed. Thus, flow of an image which Is to be photographed in the mid-exposure zooming mode may be rendered smooth and free from inconsistent density.

In Fig. 19, the control circuit of the camera 10 having the mid-exposure zooming function will be described hereinbelow, with reference to the fifth embodiment of the invention. Explanation will be omitted for portions which are identical with those in the fourth embodiment.

The control section 1 further comprises comparison means 53. This comparison means 53 is adapted to compare a variation in the focal length as detected by the focal length variation detection means 491 with a focal length variation factor C which has been preset beforehand.

The focal length distance variation detection means 491 is adapted to detect a variation in the focal length at the time of zooming in response to codes which are read by the code brush 28 from the code plate 22. The motor speed control means 47 controls the rotation speed of the zooming motor 4 to make consistent a variation in the variation of the focal length at the time of the zooming operation.

The operation of this embodiment will be described hereinbelow, with reference to Figs. 20-22.

When the release switch 15 is halfway depressed to turn ON the light measuring switch SWS in step S96, it is judged whether the mid-exposure zooming operation is about to be taken or not in step S97. The process advances to step S98 if the mid-exposure zooming operation Is about to be taken, 4 i k, and the process advances to step S4 if the mid-exposure zooming operation is not intended (Fig. 10). The process to be taken af ter this step S4 is the same as that shown in Fig.10.

Next, the shutter dial 51 is operated to preset a proper shutter speed.

In step S98, it Is judged whether the Tv value (shutter speed) is slower than the X contact synchronous speed (strobe synchronous speed).

As a result, the process is repeated in step S97 if the shutter speed is not slower than the X contact synchronous speed, and the process advances to step S100 if it is slower than the X contact synchronous speed.

In step S100, the Tv value B as preset by means of the shutter dial is recorded in the shutter speed read-in means 50 to advance the process to step S101.

In step S101, it is judged whether or not the wide-angle switch 29 is ON or not; the process advances to step S102 if the switch is turned ON to drive the zoom motor 4 to by-pass it to step S98. If the wide-angle switch 29 is not turned ON, the process advances to step S103.

In step S103, it is judged whether the telescoping switch 30 is turned ON, and. the process advances to step S102 if the telescoping switch 30 is turned ON, and the process advances to step S104 it the switch is not turned ON.

In step S104, a focal length fl for the termination of the zooming operation is read in to the memory means 45 to advance the process to step 105.

In step S105, it is judged whether the start switch 31 is turned ON or not; the process returns to step S100 if the start switch 31 is not turned ON, and the process advances to step S106 if the switch is turned ON.

In step S106, it is judged whether the wide-angle switch 29 is ON or not; the process jumps to step S109 if 4 1 -24the switch is turned ON, and the process advances to step S108 if the switch is not turned ON.

In step S108, it is judged whether the telescoping switch 30 is ON or not; the process is repeated in step S105 if the switch is not turned ON, and the process advances to step S109 if the switch is turned ON so as to read-in the zooming direction (step S109).

In step S110, the zoom motor 4 is actuated by means of the zooming starting means 8, and the release switch is actuated by means of the exposure starting means 9 In step S111 to generate release signals for bringing the step further to step S112.

In step S112, a variation in the focal length as read in by the focal length variation detection means 499 is monitored to read in the focal length f2 for the starting of the zooming operation, and then the process is advanced to step S113.

In step S113, a variation A f in the focal length is calculated, and the process is advanced to step S114.

In step S114, the count means 14 is actuated to count down the time t, thereby calculating A f/A t (variation in time).

In step S121, the comparison means 53 compares A f/A t as calculated in the step S114 with a variation factor C In the focal length as preset beforehand.

As a result, the process advances to steps S122 if A f/A t>c, thereby reducing the rotation speed of the zoom motor 4 by means of the motor speed control means 47.

In turn, the process advances to step S123 if A f/A t<CI thereby increasing the rotation speed of the zoom motor 4 by means of the motor speed control means 47.

When equality is reached, the process advances to step S124, wherein it is judged whether the switch 2CSW is ON or not. The process returns back to step S112 if the switch is not turned ON, and the process advances to step 0 S125 to stop the motor 4 and goes to Return if the switch is turned ON.

Consequently, the embodiment permits the user to perform the mid-exposure zooming operation in a convenient manner, thereby allowing him or her to control the rotation speed of the zoom motor 4 appropriately in terms of a variation factor in the focal length as preset beforehand. This arrangement may permit the user to keep a variation factor in the focal length at a constant at the time of zooming, thereby allowing the user to provide a picture having a smooth flow of image.

The sixth embodiment of the control circuit for the camera 10 will be described hereinbelow, with reference to Fig. 23. The control section 1 in this embodiment is different from the control section 1 in the fourth embodiment as shown in Fig. 15 in that zoom start limit means 54 are provided. The zoom start limit means 54 serves to actuate the mid-exposure zooming only when the shutter speed is slower than the X contact synchronous speed as read in by the shutter speed read means 50.

The zoom termination means 24 and the motor speed control means 47 have the following functions. The zoom termination means 24 stops the driving of the zoom motor 4 by issuing a zoom termination signal. The motor speed control means 47 functions to stop the zooming operation when the power zoom lens 13 reaches a zoom-ending focal length f 1 as stored in the focal length memory means 45 on an mid-exposure zooming, thereby terminating the zooming operation.

The operation of this embodiment will be described hereinbelow, with reference to Figs. 24-25.

In step S130, when a user depresses the release switch halfway to turn ON the light measuring switch SWS, it allows the user to judge whether the mid-exposure zooming is about to be taken In step S131. If the K mid-exposure zooming is intended, the process advances to step S132. The process is advanced to step S4 if the mid-exposure zooming is not intended (Fig. 10).

1 ( b 1 a n k) In step S132, the zooming start limit means 54 serves to judge whether the TV value as preset by means of the shutter dial 51 is slower than the X contact synchronous speed. As a result, when the shutter speed is faster than the X contact synchronous speed, the process returns back to step S131 and then is further advanced to step S4, whereas the process advances to step S133 if the shutter speed is slower than the X contact synchronous speed.

In step S133, the TV value B as preset by means of the shutter dial 51 is read in by the shutter speed read-in means 50 to advance the process to step S134.

In step S134, it is judged whether the wide-angle switch 29 is ON or not. If the switch is turned ON, then the process advances to step S135 to drive the zoom motor 4 to by-pass the process to step S132. The process is then advanced to step S136 if the wide-angle switch 29 is not turned ON.

In step S136, it is judged whether or not the telescoping switch 30 is ON. As a result, the process advances to step S138, if the telescoping switch 30 is turned ON, and the process advances to step S138 if the telescoping switch 30 is turned OFF.

In step S138, it is judged whether the memory switch 32 is ON or not. The process is repeated from steps S134, if the switch is not turned ON, and the process advances to step S139 if the switch is turned ON. By releasing the memory switch 32 while the memory switch 32 is being depressed for the zooming operation, the focal length at that position is memorized, thereby allowing the user to read in the focal length fl for the termination of the zooming (step S139).

In step S140, the operation of reading in the focal length f2 for the starting of the zooming is carried out.

In step S141, it is judged whether or not the wide-angle switch 29 is ON. The process advances to step S142 if the switch is turned ON, whereas the process is 1 1 k -28advanced to step S143 if the switch is not turned ON.

In step S142, the lens is zoomed toward a wide-angle position by the focal length of A f, thereby advancing the process to step S145.

In step S143, it is judged whether the telescoping switch 30 is turned ON. The process advances to step S144 if the switch is turned ON, and the process returns back to step S141 if the switch is not turned ON.

In step S144, the lens is zoomed to move toward a telescoping position by the focal length of A f, thereby advancing the process to step S145.

In step S145, it is judged whether or not the start switch 31 is ON. The process advances to step S146 if the switch is turned ON, and the process is repeated in step S145 if the switch is not turned ON.

Then, actuation of the zoom motor 4 is initiated (step S146) to cause the exposure starting means 9 to turn ON the release switch, thereby actuating the switch to generate the release switch for the starting of the exposure operation (step S147).

In step 154, the focal length as read in by the focal length detection means 49 is monitored to advance the process to step S155.

In step S155, it is judged whether f=fl, that is, whether the focal length f has reached the focal length fl for the termination of the zooming operation.

If not equali the process returns back to step S154, and the process is advanced to a step S156 if the result is equal.

In step S156, the motor speed control means 47 stops the operation of the zoom motor 4 to thereby advance the process to step S157.

In step S157, it is judged whether or not the switch 2CSW is ON. The process advances to step S158 if the switch is turned ON, and the process is repeated in step S157 if the switch is not turned ON.

In step S158, the exposure is completed and data such as the focal length fl for the zoom termination and the like are erased to let the process go to Return.

Thus, the embodiment allows the user to carry out the mid-exposure zooming operation automatically and conveniently without relying on the user's skilled technique. Moreover, since the zoom motor 4 is rendered inoperative upon the motor speed control means 47 reaching the focal length fl as stored for the zoom termination during the mid-exposure zooming, the user can stop the zooming operation at any given moment at a zooming termination focal length fl which has been preset by looking at an object through the finder to verify the position. Consequently, it may be possible for the user to avoid the inconvenience of the zooming operation being only partially finished upon completion of the exposure operation, and thus the zoomed photographing effect may not be realized sufficiently despite the employment of the mid-exposure zooming operation. In this way, the user can imagine the finished photograph of an object before it is actually taken.

In the meantime, it may also be possible to design the embodiment such that the focal length f2 for the zoom starting may be varied in accordance with the TV value. On presetting the focal length fl for the zoom termination, it may also be possible to arrange the embodiment such that a warning signal can be emitted should the focal length fl may not be realized within the total exposure time in accordance with the shutter speed as preset at that moment.

Next, the seventh embodiment of the present invention will be described hereinbelow. The control circuit in this embodiment is identical to that in the sixth embodiment of Fig. 26, except for the functions of the zoom termination means 24 and the motor speed control means 47.

That is, the zoom termination means 24 in this 0 11 1 -30 embodiment is adapted to stop the zoom motor 4 upon the count means 14 reaching a preset level relative to a shutter speed as read in by the shutter speed read-in means 50. The motor speed control means is adapted to control the zoom motor 4 such that a proper rotation speed of the zoom motor 4 can be calculated in accordance with the zoom termination focal length fl, the zoom starting focal length f2, each of which has been stored in the focal length memory means 45, and a shutter speed Tv which has been input into the shutter speed read means 50. In addition, the motor is controlled so as to rotate at the speed thus calculated.

The operation of the camera with the seventh embodiment of the present invention is illustrated in Figs. 26-28.

In step S161, the release switch 15 is halfway depressed to turn ON the light measuring switch SWS, thereby allowing the user to judge whether the mid-exposure zooming operation is about to be used. If the user intends to take the mid-exposure zooming operation, the process is advanced to step 163, and the process advances to step S164 if the mid- exposure zooming operation is not intended.

In step S164, it is judged whether or not the wide-angle switch 29 is ON. The process advances to step S179 if the switch is turned ON, thereby driving the zoom motor 4. The process advances to step S180 if the switch is not turned ON.

In step S180, it is judged whether the telescoping switch 30 is turned ON. If the switch is turned ON, the process advances to step S179 to drive the zoom motor 4, and the process is advanced to step S181 if the telescoping switch 30 is not turned ON.

In step S181, it is judged whether or not the shutter release switch 15 is ON, and the process is repeated if the switch is not turned ON. The process is advanced to step S182 if the switch is turned ON.

A 1{ In step S182, a release signal is emitted by means of the exposure starting means 9 to advance the process to step S183.

In step S183, it is judged whether or not the switch 2CSW is ON, and the process is repeated if the switch is not turned ON. The process Is advanced to step S184 for return.

In step S163, a zooming start limit means 54 acts to judge whether the Tv value as preset by the shutter dial 51 is slower than the X contact synchronous speed. AS a result, the process returns to step S162 to further advance to step S164 if the shutter speed is faster than the X contact synchronous speed. Consequently, if a preset shutter speed is faster than the X contact synchronous speed, a simultaneous operation of the wide-angle switch 29 and the release switch 15, and between the telescoping switch 30 and the release switch 15 will never occur. This serves to avoid a slit exposure in which a highlighted slit illuminated by the strobe light is formed on a picture and uneven density of images which would otherwise be caused due to the mid-exposure zooming operation.

In step S165, the Tv value B as preset by means of the shutter dial 51 is read in by the shutter speed read-in means 50 to advance the process to step S166.

In step S166, it is judged whether or not the wide-angle switch 29 is turned ON, and the process advances to step S167 if the switch is turned ON to drive the zoom motor 4 to skip. to step S163. The process is advanced to step S168 if the wide-angle switch 29 is not turned ON.

In step S168, It is judged whether or not the telescoping switch 30 is turned ON, and the process is ad.vanced to step S167 if the telescoping switch 30 is turned ON. The process is advanced to step S169 if the telescoping switch 30 is not turned ON.

In step S169, it is judged whether or not the memory switch 32 is turned ON. The process is returned to step S166 if the switch is not turned ON, whereas the process is -32 advanced to step 170 if the switch is turned ON. By releasing the memory switch 32 while the user depresses the memory switch 32 with the zooming mode, its focal length at that position can be stored.

This procedure allows the user to read the zooming termination focal length fl in the step 170.

In step S171, the focal length f2 for the zooming operation starting is read in.

In step S172, it is judged whether the wide-angle switch 29 is turned ON. The process advances to step S173 if the switch is turned ON. If the switch is not turned ON, the process is advanced to step 174.

In step S173, the lens is driven to move toward the wide-angle position by the amount of a focal length equivalent with the magnitude of A f, and the process then advances to step S176. This magnitude A f is obtained as described below.

Assuming that the focal length at the time of the EU (exposure zoom) termination is fl [mm], the Tv value is B [sec], the rate at which the focal length is caused to vary is Vf, and a constant is set as K which is defined to stop the zooming operation when 80% of the total exposure time period is passed relative to the shutter speed, then it follows that:

A f=Vfx K x B = 0.8W-B In step 174, it is judged whether or not the telescoping switch 30 is turned ON. The process is advanced to step S175 if the switch is ON, and the process returns back to step S172 if the switch is not turned ON.

In step S175, the lens is zoom-driven toward the telescoping side by the amount of focal length equivalent to the magnitude of A f.

In step S176, it is judged whether the start switch 31 is turned ON. The process is advanced to step S177 if the switch is turned ON, and the process is repeated at step S176 if the switch is not turned ON.

0 In step S177, the actuation of the zoom motor 4 is initiated.

In step S178, the exposure starting means 9 turns ON the release switch to emit release signals, thereby allowing the user to initiate the exposuring operation.

In step S185, a focal length which has been read in by means of the focal length detection means 49 is monitored, and then the process is advanced to step S186.

In step S186, It Is judged whether a relation such as f2 = fl +A f is present. The process returns back to step S185 if the above equation is not present and then is advanced to step S187 if the above equation is present.

In step S187, the drive of the zoom motor 4 is stopped to advance the process to step S188.

In step S188, it is judged whether or not the switch 2CSW is ON. The process advances to step S189 if the switch is turned ON, and the process is repeated if the switch is not turned ON.

In step S189, the exposuring operation is completed, and moreover the Tv value and the focal length fl and A f which have been input are erased to let the process go to Return.

In this embodiment, the mid-exposurezooming operation may be carried out automatically and conveniently without relying on the user's ski 1 ledtechnique. Furthermore, since the zooming starting means 54 limits the operation of the mid-exposure zooming operation when the shutter speed is faster than a preset reference shutter speed (X contact synchronousspeed), it can reliably avoid the occurrence of the slit exposure and a problem that the mid-exposure zooming operation is carried out at the slit exposure, thereby creating a picture where the density of the image is uneven.

Next, the eighth embodiment of the invention will be described hereinbelow. The relationship between the focal length f and the F number of the diaphragm is shown in Fig. 33. This relationship between the focal length f and the F number is kept in constant proportion. Thus, as the F number is varied in response to the focal length f, an exposure amount to be imposed on a film surface varies with the value F, thereby causing an uneven exposure. The embodiment permits the user to perform the mid-exposure zooming operation automatically and conveniently, thereby further eliminating the occurrence of such an uneven exposure.

In Fig. 29, the arrangement of the power lens is identical to that as shown in Fig. 4. The relationship between the F number and the focal length f for the power zoom lens is identical to that shown in Fig. 33 in the full zooming range.

Signals which are read in through a decoder 67 are output to a lens CPU 66. The lens CPU 66 determines the focal length f and its corresponding F number with, as its basis, the output from the decoder 67. Those data are output to a control section 84 of a camera body 80.

The control circuit 84 is usually composed of microcomputers to drive the zoom motor 4 for a zooming operation in accordance with the program which has been stored in the internal ROM.

Some of the beam of light flux from the object t be photographed which has passed through lens groups L1 and L2 is transmitted through a half mirror section of the main-mirror 81 and reflected by the sub-mirror 82 for introduction Into a CW distance measuring sensor 83. This distancemeasuring sensor 83 is of a phase-difference detection type, and it outputs to the control section 84 the.' phase information of images which have been halved. The control section 84 executes a pre-director computation in accordance with phase difference information to obtain a magnitude for defocusing, thereby allowing the user to adjust the focus. Such a mechanical arrangement Is known

1 1 1 4 per se.

The camera body 80 is provided with the light measuring switch SWS, the mirror 81, the shutter release.

switch 15 for initiating the exposure operation by driving the shutter and the aperture (not shown), and the mode selection switch 16 for selecting the mid-exposure zooming mode, all of which components are connected with the Inlet port of the control section 84.

The embodiment has the mode selection switch 16 which is used to select the mid-exposure zooming mode. While on the mid-exposure zooming mode, either the wide-angle switch 29 or the telescoping switch 30 is actuated to select either the telescoping zoom or the wide-angle zooming mode, respectively.

Alternatively, the wide-angle zooming may be taken when the power zoom lens 13 is in a telescoping position, and the telescoping zooming operation may be available when the power lens is in a wide-angle position, or the lens may be zoomed in a reverse direction when the focal length at the starting of the exposure operation is either in a wideangle position or a telescoping position.

When the power zoom lens 13 is zoomed from the focal length fo to the focal length fn, the F number F is made to vary f rom the value Fo to the value Fn as shown in Fig. 33. In the eighth embodiment, the zooming speed is increased to the wide-angle position where the F number is small (diaphragm aperture is large), and the zooming speed is reduced to the telescopic side where the F number F is large (diaphragm aperture is small). This variation in speed serves to keep constant the intensity of the incident beam, i.e., the exposure amount on the film surface in the entire zooming ranges.

This variation in the zooming speed may be achieved by varying the rotation speed of the zoom motor 4, or by varying the profile of the cam grooves 72, 73 in the cam ring 19 while keeping a constant rotation speed of the 1 t zoom motor 4.

Adjustment of the motor speed may be achieved by varying the pulse frequency in a case where the zoom motor 4 is constituted by a pulse motor, or by varying a voltage in a case where the zoom motor 4 is formed f rom a DC brush motor. In either case, the rotation speed for each of the focal lengths f may be determined from the equation R = g(F)Ro where, Ro is a rotation speed at the wide-angle position and q(F) =112(lotylogFO)/Locz.

This relationship is shown in the graph in Fig. 30.

In order to keep the rotation speed of the zoom motor 4 at a constant, the zooming speed may be made variable by varying the profiles of the cam grooves 72 and 73. In this case, the focal length graduation range can be expressed by the equations of: H = h(f) Ho, where Ho is a graduation range around the wide-angle position, and h(f) = 2(locF-1oxFo)/lox2 This relationship is shown in the graph of Fig. 31.

One example of this distance graduation given this condition is indicated in Fig. 32. The distance graduation ranges P, 1-.e 4 as shown in Fig. 32 may be obtained from the following equation:

f P, = 1 fo h(f)df Fig. 34 shows a distance graduation where a focal length is maintained at a constant level relative tothe rotation angle of the zoom operating ring 13.

Consequently, the embodiment permits the user to carry out the mid-exposure zooming operation automatically and conveniently without relying on his or her skilled-technique, and the user can avoid the uneven exposure result by exposing an image which is variable with the zooming operation at a constant intensity despite the i ? i 1 1k -37full-open F number or preset F number being variable due to the zooming operation. Furthermore, the zooming speed is variable in a power zoom lens in accordance with the change of the F number, thereby permitting the user to expose the image with a constant intensity of light irrespectively of the focal length, and thus to photograph an image having a flow which Is free from any uneven density under any condition.

1

Claims

CLAIMS:

1. A camera having a mid-exposure zooming function comprising:

2. A camera according to Claim 1, wherein said mid-exposure execution means comprises zooming starting means for starting the driving of said zoom motor based on the operation of said trigger switch, exposure starting means for starting exposure based on the actuation of said zooming starting means, and means for detecting sufficient conditions for enabling the exposure starting means to start exposure synchronously with the operation of the zooming starting means.

3. A camera according to Claim 2, wherein said means for detecting sufficient conditions include a mid-exposure zooming function for counting time synchronously with the zooming starting means until sufficient conditions for enabling the exposure starting means to start exposure have been identified.

4. A camera according to Claim 3, wherein said means for detecting sufficient conditions comprise counting means.

5. A camera according to claim 2 or 3, wherein said means for detecting sufficient conditions monitors variation of the focal length synchronously with the operation of the zooming starting means, and identifies a sufficient focal length which is to be the sufficient condition for starting exposure.

6. A camera according to any preceding claim, wherein said camera further comprises a start switch by which the zooming starting means is operated.

7. A camera according to Claim 3, wherein said time counted by the midexposure zooming function is the period 1 1 1 1 -39during which the zooming speed becomes constant.

8. A camera according to Claim 3, wherein said predetermined time is set at 1/10 of the whole exposure time.

9. A camera according to Claim 1, wherein said mid-exposure zooming execution means comprises zooming starting means for starting the driving of said zoom motor based on the operation of said trigger switch, exposure starting means for starting exposure based on the actuation of said zooming starting means, counting means for counting exposure time synchronously with the actuation of said zooming starting means, means for reading in a preset shutter speed, and zooming termination means for stopping the driving of said zoom motor when the value counted by said counting means reaches a predetermined rate of the whole exposure time corresponding to the shutter speed read in said shutter speed reading-in means.

10. A camera according to Claim 9, wherein said means for reading in a preset shutter speed further comprises a shutter dial to set a shutter speed which is to be read in the means for reading in a preset shutter speed.

11. A camera according to claim 9 or 10, wherein said predetermined rate of the whole exposure time is 80%_ of the whole exposure time.

12. A camera according to Claim 1, wherein said zooming execution means comprises zooming starting means for starting the driving of said zoom motor based on the operation of said trigger switch, exposure starting means for starting exposure based on the actuation of said zooming starting means, focal length detection means for detecting the focal length of said zoom lens, focal length memory means for memorizing focal length upon starting of zooming and focal length upon completion of zooming, means for reading in a preset shutter speed, and motor speed controlling means for controlling the driving speed of said zoom motor on the basis of focal length data memorised by said focal length memory means and shutter mid-exDosure -40speed data memorised by said shutter speed reading-in means.

13. A camera according to Claim 12, wherein said camera further comprises a memory switch, and said focal length memory means operates based on the operation of said memory switch.

14. A camera according to claim 12 or 13, wherein said means for reading in a preset shutter speed further comprise a shutter dial to set a shutter speed which is to be read in the means for reading in a preset shutter speed.

15. A camera according to Claim 1, wherein said mid-exposure zooming execution means comprises zooming starting means for starting the driving of said zoom motor based on the operation of said trigger switch, exposure starting means for starting exposure based on the actuation of said zooming starting means, focal length variation detection means for detecting the amount of variation of focal length undergone by said zoom lens, comparison means for comparing variation of focal length detected by said focal length variation detection means with a predetermined variation rate of focal length, and motor speed controlling means for controlling the rotation speed of said zoom motor based on the result of the comparison performed by said comparison means so as to maintain the variation rate of focal length upon zooming at a.constant value.

16. A camera according to Claim 15, wherein said motor speed controlling means increases rotation of the zoom motor when the focal length variation detected by the focal length variation detection means is larger than the predetermined variation rate of focal length, and said motor speed control means decreases rotation of the zoom motor when the focal length variation detected by the focal length variation detection means is smaller than the predetermined variation rate for focal length.

17. A camera according to Claim 1, wherein said mid-exposure zooming starting means comprises zooming starting means for starting the driving of said zoom motor 1 1 1 k -41 based on the operation of said trigger switch, exposure starting means for starting exposure based on the actuation of said zooming starting means, memory means for memorizing the focal length upon completion of zooming, and motor controlling means for stopping said zoom motor when the focal length reaches said focal length upon completion of zooming as memorized in said focal length memory means during mid-exposure zooming.

18. A camera according to Claim 17, wherein said zoom lens includes a memory switch, and said focal length memory means for memorizing the focal length upon completion of zooming operates based on the operation of said memory switch.

19. A camera according to Claim 1, wherein said mid-exposure zooming execution means comprise zooming starting means for starting the driving of said zoom motor based on the operation of said trigger switch, exposure starting means for starting exposure based on the actuation of said zooming starting means, means for reading-in a preset shutter speed, and zooming starting limiting means for allowing operation of said midexposure zooming starting means only when the shutter speed read in the means for reading-in a preset shutter speed is slower than a predetermined standard shutter.speed.

20. A camera according to Claim 19, wherein said predetermined standard shutter speed is a synchronous speed of X contact.

21. A camera according to Claim 1, further comprising a mid-exposure zooming mode for execution of zooming during exposure, and control means for varying the zooming speed during exposure in accordance with the variation of the diaphragm performed by zooming.

22. A camera according to Claim 21, wherein the zooming speed is set such that it becomes faster when the diaphragm is bright, and slower when it is dark.

23. A camera having a mid-exposure zooming function substantially as herein described with reference to the accompanying drawings.

Published 1991 at 7he Patent Office. State House. 66171 High Holborn. London WC1R47P. Further copies maybe obtained from Sales Branch. Unit 6, Nine Mile Point, Cwmfelinfach. Cross Keys, Newport. NPI 711Z. Printed by MUltipleX techniques ltd. St Mary Cray. Kent.