WO2005076597A2 - Camera and method for setting exposure condition of the same - Google Patents

Camera and method for setting exposure condition of the same Download PDF

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Publication number
WO2005076597A2
WO2005076597A2 PCT/JP2005/002099 JP2005002099W WO2005076597A2 WO 2005076597 A2 WO2005076597 A2 WO 2005076597A2 JP 2005002099 W JP2005002099 W JP 2005002099W WO 2005076597 A2 WO2005076597 A2 WO 2005076597A2
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WO
WIPO (PCT)
Prior art keywords
film
exposure
speed
camera
value
Prior art date
Application number
PCT/JP2005/002099
Other languages
French (fr)
Other versions
WO2005076597A3 (en
Inventor
Minoru Ishiguro
Takeichi Tatsuta
Mitsuhiro Uchida
Original Assignee
Fujinon Corporation
Fuji Photo Film Co., Ltd.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fujinon Corporation, Fuji Photo Film Co., Ltd. filed Critical Fujinon Corporation
Publication of WO2005076597A2 publication Critical patent/WO2005076597A2/en
Publication of WO2005076597A3 publication Critical patent/WO2005076597A3/en

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Classifications

    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03B—APPARATUS OR ARRANGEMENTS FOR TAKING PHOTOGRAPHS OR FOR PROJECTING OR VIEWING THEM; APPARATUS OR ARRANGEMENTS EMPLOYING ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ACCESSORIES THEREFOR
    • G03B7/00—Control of exposure by setting shutters, diaphragms or filters, separately or conjointly
    • G03B7/08—Control effected solely on the basis of the response, to the intensity of the light received by the camera, of a built-in light-sensitive device
    • G03B7/091—Digital circuits
    • G03B7/097—Digital circuits for control of both exposure time and aperture

Definitions

  • the present invention relates to a film-loading type camera in which an exposure condition is automatically set and a method for setting an exposure condition of the same.
  • Background Art Fully automatic compact cameras are in widespread use, which automatically sets an exposure condition while requiring a user to do nothing except for loading a film and which permits the user to take a satisfactory photograph by simply depressing a shutter release button.
  • the cameras of this type are configured to automatically perform the focus control and control of auxiliary light, as well as the exposure control, and permit everyone to take a photograph by merely powering up and releasing the shutter.
  • Such cameras have a function of effecting correct exposure for a major subject by automatic light emission from a built-in flash unit even in scenes of dark subject such as indoor scenes and night scenes.
  • the flash light presents the convenience of enabling photography in any environments as described above, but photographs taken with flash light often lack the realistic atmosphere in the scene for the following reasons: - the flash light may not reach the background to result in dark, dismal description relative to the major subject; and - the main subject is taken with light which does not exist in the scene, and thus may give an unnatural impression.
  • Patent Document 1 discloses the invention in which the film speed is set to a lower value where the subject is not more than a specific luminance.
  • Patent Document 2 discloses the invention in which the frequency of occurrence of hand-shakes is raised and inconveniences compact-camera users liking to easily enjoy photography since the system sensitivity becomes low with a low-speed film loaded. It is therefore an object of the present invention to provide a camera capable of automatically taking a photograph with good atmosphere while being free of the aforementioned defects, even if such an auxiliary light as a flash light is not used.
  • the exposure setting unit carries out the exposure compensation only when the photometric value is not more than a specific value.
  • the exposure setting unit carries out the exposure compensation when the camera is loaded with a film of a film speed with which the system sensitivity Ls is not more than 4.
  • the maximum shutter speed T 0 is restricted not to exceed a certain value.
  • the exposure setting unit calculates the system sensitivity Ls with the upper time limit T 0 of 1/30 seconds if the upper time limit To is not set to a specific value. By adopting this constitution, it is feasible to diminish the possibility of hand-shake effect even if the hand-shake control shutter speed is not set.
  • the exposure setting unit may include a photometer measuring luminance of ambient light in a photographic field; a film speed sensor detecting a film speed of the loaded film; and a controller setting the exposure condition with calculating the system sensitivity Ls by a measurement signal fxom the photometer and a detection signal from the film speed sensor in order to control opening operation of a shutter. Further, it is preferable that no auxiliary light is emitted when the exposure setting unit ca ⁇ rries out the exposure compensation. By adopting this constitution, it is feasible to avoid an artificial impression of the subject. Moreover, the present invention can be described as a method for setting an exposure condition of a film-loading type camera with similar operations and effects.
  • Fig. 1 is a perspective view to show the appearance of a camera according to the first embodiment of the present invention.
  • Fig. 2 is a perspective view to show the appearance of the camera according to the first embodiment of the present invention.
  • Fig. 3 is an illustration to illustrate a display in the camera of Fig. 1.
  • Fig. 4 is a schematic diagram to show a configuration of the camera of Fig. 1.
  • Fig. 1 is a perspective view to show the appearance of a camera according to the first embodiment of the present invention.
  • Fig. 2 is a perspective view to show the appearance of the camera according to the first embodiment of the present invention.
  • Fig. 3 is an illustration to illustrate a display in the camera of Fig. 1.
  • Fig. 4 is a schematic diagram to show a configuration of the camera of Fig. 1.
  • Fig. 1 is a perspective view to show the appearance of a camera according to the first embodiment of the present invention.
  • Fig. 2 is a perspective view to show the appearance of the camera according to the
  • FIG. 5 shows an example of spectral sensitivity of a silicon photodiode photometric sensor equipped with an infrared cut filter.
  • Fig. 6 shows spectral energy distributions of tungsten light (solid line as CIE standard source A) and a light source according to daylight (dotted line as CIE standard source C) .
  • Fig. 7 shows typical spectral sensitivities off a color negative film (solid line as a blue-sensitive layer, dotted line as a green-sensitive layer, and chain line as a red-sensitive layer) .
  • FIG. 8 is an illustration showing an example of: a flowchart from depression of a release button to completion of photography in an automatic mode of the camera in Embodiment 1 according to the present invention.
  • Fig. 8 is an illustration showing an example of: a flowchart from depression of a release button to completion of photography in an automatic mode of the camera in Embodiment 1 according to the present invention.
  • Fig. 8 is an illustration showing an example of: a flowchart
  • FIG. 9 is a ⁇ Ev-Bv chart wherein a solid line indicates an exposure control in the automatic mode where a film of the ISO speed of 1600 is loaded on the camera of Embodiment 1 and wherein a dashed line indicates an exposure control in the automatic mode where a film of the ISO speed of 800 is loaded on the same camera, in which the horizontal axis represents the photometric value (Bv values, together with L- values) by centerweighted metering means and in which the vertical axis represents the exposure compensation amount ⁇ Ev [EV] .
  • Fig. 10 is a program chart in the automatic mode where the film of the ISO speed of 1600 is loaded on the camera of Embodiment 1 according to the present invention.
  • Fig. 1 is a perspective view showing the front- side appearance of a camera according to the first embodiment of the present invention
  • Fig. 2 a perspective view showing the back-side appearance of the camera according to the embodiment.
  • the camera of the present embodiment is an application of the present invention to a lens shutter camera to be loaded with a film cartridge of the 135 film format.
  • This camera is provided with a release button 11 at an upper end of a camera body 10.
  • a lens barrel 13 equipped with a photographic lens 12 is mounted in the central part of the front surface of the camera body 10.
  • the lens barrel 13 used herein is a photographic lens barrel, for example, comprised of a monofocal lens with the focal length of 24 mm and full-aperture F2.0, and a shutter and being capable of autofocus operation.
  • the light projector 14 and the light receiver 16 constitute a range finder for measuring the distance to the subject, for example, based on the principle of triangulation.
  • the camera body 10 is also provided with a photometer 18.
  • the photometer 18 functions as a photometric means for measuring the luminance of ambient light in a photographic field.
  • This photometer 18 is, for example, one equipped with an SPD device (incorporating an infrared cut filter on the optical path) as a centerweighted averaging metering sensor.
  • This SPD device is approximately directed onto the optical axis of the photographic lens optical system.
  • a shutter 19 is incorporated on the optical axis of the photographic lens 12 inside the camera body 10.
  • the shutter 19 includes sectors also used as diaphragm blades for determining an exposure amount necessary for the film.
  • This shutter 19 is, for example, a two-blade lens shutter having the f-number of 2.0 (f/2.0) at full opening and the control range Ev of 2 to 16 [EV] .
  • a finder eyepiece window 41 and a warning indicator 42 provided in the upper part on the back side of the camera body 10.
  • the warning indicator 42 is, for example, one having a light emitting device of a two color type of red and green.
  • a back lid 43 is provided below the finder eyepiece window 41 and the warning indicator 42. While the back lid 43 is opened, a film cartridge is loaded into the camera body 10.
  • a battery lid 44 is provided beside the back lid 43. While the battery lid 44 is opened, a battery is loaded into the camera body 10.
  • the back lid 43 is provided with a main switch 45, a mode switch 46, date switches 47, and a display 50.
  • the main switch 45 is a switch for switching the whole camera on and off.
  • the mode switch 46 is a switch for enabling switching among photography modes of the camera.
  • the date switches 47 are switches used for setting, correction, etc. of the date and others.
  • the display 50 is a display means for displaying a selected photography mode of the camera, the date, the number of remaining frames of the film, and so on.
  • This display 50 is, for example, an LCD.
  • Fig. 3 shows an enlarged view of the display 50.
  • the display 50 is provided, for example, with a photography mode display 51, a date display 52, and a number-of-frames display 53.
  • the photography mode display 51 is a portion for displaying a photography mode selected and includes an autophotography mark 51a, a flash photography mark 51b, a non-flash photography mark 51c, and a natural photography mark 51d.
  • the date display 52 is a part for displaying the date, for example.
  • the number-of- frames display 53 is a part for displaying the number of remaining frames of the film.
  • Fig. 3 shows the display 50 in which all the marks and others are in a displayed state.
  • Fig. 4 is a block diagram schematically showing an electric configuration of the camera according to the present embodiment.
  • the camera of the present embodiment is provided with a controller 20.
  • the controller 20 performs the control of the entire camera and includes, for example, a CPU, a ROM, a RAM, an input signal circuit, an output signal circuit, and so on.
  • the ROM of the controller 20 stores programs for control processing and arithmetic processing.
  • the RAM of the controller 20 stores various data used in the control processing and arithmetic processing.
  • the photometer 18, the shutter 19 and this controller 20 are the minimum elements for constituting an exposure setting unit 80 to set an exposure condition, which will be described later.
  • the display 50 is connected to the controller 20.
  • the display 50 provides indications of a selected photography mode, the date, the number of remaining frames of the film, etc. in accordance with a display control signal from the controller 20.
  • the main switch 45, the mode switch 46, and the date switches 47 are connected to the controller 20.
  • the controller 20 powers the camera on and off in response to input at the main switch 45.
  • the controller 20 sets or changes the photography mode in response to input at the mode switch 46.
  • the controller 20 also sets or changes the date and others in response to input at the date switches 47.
  • the light projector 14 and the light receiver 16 constitute a ranging calculation unit, and each of them is connected to the controller 20.
  • the controller 20 outputs an emission control signal to the light projector 14 to perform a light projection control.
  • the controller 20 makes the light receiver 16 receive reflected light of the projected light, and detects a distance to a subject, based on the received light signal.
  • the flash unit 17 is connected to the controller 20.
  • the controller 20 outputs an emission control signal to the flash unit 17 under predetermined conditions to make the flash unit emit light.
  • the photometer 18 is connected to the controller 20.
  • the controller 20 receives a measurement signal from the photometer 18 and converts the luminance of ambient light to a Bv value of the APEX (Additive System of Photographic Exposure) unit.
  • the shutter 19 is connected to the controller 20.
  • the controller 20 makes the shutter 19 perform an opening operation according to an exposure control when the release button 11 is depressed.
  • the battery 61 is connected to the controller 20.
  • the battery 61 is a power supply for supplying power to each part of the camera.
  • the controller 20 determines whether the battery 61 stores the amount of electricity enough for the photographic operation and others.
  • An external memory 62 is connected to the controller 20.
  • the external memory 62 stores various control parameters and others.
  • the external memory 62 is, for example, an EEPROM.
  • a release switch 63 is connected to the controller 20.
  • the release switch 63 is a switch to be changed over with depression of the release button 11. With input of the release switch 63 the controller 20 determines that the release button 11 was depressed.
  • a date copier 64 is connected to the controller 20.
  • the date copier 64 is a copy mechanism for copying the date and others onto the film.
  • a film speed sensor 65 is connected to the controller 20, and the controller 20 receives a detection signal from the film speed sensor 65.
  • the film speed sensor 65 is a film speed detecting means for detecting a film speed of the film loaded in the camera body 10.
  • the film speed sensor 65 reads the CAS code indicated on the cartridge containing the film, to detect the film speed.
  • the film speed sensor 65 has four conducting terminals (one of which is a common terminal) for reading the upper three bits inside the film cartridge chamber. The upper three bits indicate the speed value of one step unit out of the CAS codes printed in a checkered pattern on the side face of the film cartridge.
  • the film speed sensor 65 also has a film speed setting mechanism of recognizing and setting the film speed by the CPU built in the camera on the basis of conduction signals from the terminals. In cases where there are no CAS codes or where a reading error occurs, the film speed is set to the speed of 100. The film speed is detected as an ISO (International Organization for Standardization) speed. Next, the system sensitivity of the camera will be described. In the present invention, the brightness of each scene will be indicated by an L-value in conformity with the APEX system. The L-value is defined as follows using an opening time value Tv and an aperture value Av of the lens to achieve proper exposure in use of a photographic sensitive material of the ISO speed of 100.
  • the f- nu ber of the stop of the lens is used.
  • the system sensitivity Ls is defined as a minimum L-value of brightness enabling photography without hand-shakes, and is expressed by the equation below, using the maximum shutter speed T 0 of the camera and the f-number F 0 at full opening of the camera lens, and the ISO speed (arithmetic expression) S of the sensitive material loaded.
  • the upper time limit can be determined in conformity with this assumption. Since the probability of occurrence of hand-shakes can be decreased as the shutter speed becomes faster, it is preferable to set the shutter speed as fast as possible in consideration of the necessary system sensitivity. According to the above definition of Ls, correct exposure can be made if the brightness of a scene is not less than the system sensitivity. If the brightness of a scene is not more than the system sensitivity, correct exposure will not be made and the exposure will be underexposure.
  • the film speed can be acquired in such a way that the cameras reads the speed information described on the film cartridge.
  • the film speed code called the CAS code is ndicated by five bits of either conduction or insulation of electric contacts on the cartridge, and the camera can read the information.
  • the term "a specific system sensitivity can be implemented” means that the system sensitivity calculated by the camera-controllable full-aperture diaphragm stop and hand-shake control shutter speed, and the film speed of the loaded film is not more than a certain value. Namely, a threshold is prepared on the camera side and, if a system sensitivity becomes not more than the threshold, "a specific system sensitivity can be implemented.”
  • the system sensitivity Ls for exposure control of the present invention may be any value, but preferably Ls ⁇ 4, and more preferably Ls ⁇ 3. Next, the exposure compensation of the camera will be described.
  • the major subject is a person or people illuminated by indoor illumination. If under such circumstances correct exposure is calculated based on a photometric value obtained by photometry of the camera, particularly, by the centerweighted averaging metering often used in the compact cameras, the major subject will be photographed in underexposure and will result in a dark, dismal photograph.
  • the photometric value stated herein is brightness of a scene measured by the photometric means of the camera and is indicated as a luminance value Bv according to the APEX system (the L-value is given by "Bv + 5") .
  • the cause of the above-mentioned phenomenon 1) lies in the fact that the indoor illumination is mainly illumination from the ceiling and is designed on the basis of the horizontal illuminance and illuminance near the wall, and little consideration is given to the illuminance on the vertical plane near the center of the room.
  • the illuminance on the vertical plane near the center is about 1-3 EV darker than that near the wall. Since the photometric value of the camera, particularly, the photometric value by the centerweighted averaging metering is largely affected by the illuminance on the wall surface, the exposure control based on the raw photometric value of the camera results in underexposure (insufficient exposure) of about 1-3 EV for the major subject.
  • Fig. 5 is a diagram showing typical spectral sensitivity of SPD photometer (with infrared cut filter) .
  • the photometry of the camera is performed with a photometric sensor with the spectral sensitivity range near 500-600 nm as shown in Fig. 5 (the photometric sensors widely used include CdS cells or silicon photodiodes (SPDs) with an infrared cut filter) .
  • Fig. 6 is a diagram showing spectral examples of light sources.
  • the energy distribution of the CIE standard source A (correlated color temperature: about 2850K) , which is a typical tungsten light source, has a slope against wavelength, as indicated by a solid line in Fig. 6, and the energy in the region of 400-500 nm is lower than in the region of 500-600 nm.
  • Si ( ⁇ ) the spectral sensitivity of the negative film at the wavelength ⁇ (i 0, 1, or 2 for the red-sensitive layer, the green-sensitive layer, or the blue-sensitive layer, respectively), R( ⁇ ) the reflectivity of the object at the wavelength ⁇ , and E ( ⁇ ) the spectral energy of the light source at the wavelength ⁇ .
  • the integral value calculated by this integration is an exposure amount for the color negative film. In the ordinary daylight case (correlated color temperature: about 5000K) , exposure values are at the same level for the green-sensitive layer and the blue- sensitive layer close to the spectral sensitivity of the photometric sensor, but in the tungsten light case, the exposure amount for the blue-sensitive layer becomes 1-2 EV lower than that for the green-sensitive layer.
  • This phenomenon lies in the fact that the spectrum thereof is substantially in the green light region although an ordinary photometric sensor is designed based on the spectral sensitivity of human eyes, i.e., based on the spectral sensitivity according to the standard luminous efficiency.
  • an ordinary photometric sensor is designed based on the spectral sensitivity of human eyes, i.e., based on the spectral sensitivity according to the standard luminous efficiency.
  • a and standard source C are adjusted in intensity (illuminance) thereof so that the photometric sensor with the spectral sensitivity shown in Fig. 5 provides the same photometric value and that a color negative film for daylight with the spectral sensitivities shown in Fig. 7 is exposed to their light.
  • the exposure amount for the green-sensitive layer demonstrates little change (decrease of ⁇ 0.02 EV) but the exposure amount for the blue-sensitive layer does the decrease of 1.56 EV (while the exposure amount for the red-sensitive layer shows the increase of 0.88 EV) in the case of the light source A of the lower color temperature .
  • the major subject is darker than the photometric value of the camera in many cases and the present invention has solved this problem by the exposure compensation of not less than +1.5 EV for the photometric value.
  • the exposure compensation breadth of +1.5 EV is a minimum correction amount, and the exposure compensation is preferably not less than +2 EV and more preferably not less than +3 EV.
  • the magnitude of the exposure compensation may be further corrected using information except for the photometric value. For example, where a sensor to detect color temperature is available, the exposure compensation breadth can be corrected according to the color temperature measured.
  • a preferred correction is such that the exposure compensation is +3 EV at 3000K and +2 EV at 5000K.
  • the exposure compensation method may be any method that can increase the exposure amount as a result. It may be a method of adding an exposure compensation value to the photometric value and feeding the result to an arithmetic circuit of exposure control, or a program for this exposure control may be preliminarily defined as a table against photometric values. Another method may be to perform a calculation using a result of subtraction of a desired exposure compensation amount from the film speed. In the exposure compensation of the present invention, it is preferable to change on/off of the exposure compensation and the level of the exposure compensation in accordance with brightness of the subject.
  • the purpose of the exposure compensation is to correct the influence of artificial illumination in the indoor and other circumstances, and no exposure compensation is needed under circumstances clearly different from the artificial illumination.
  • One of preferred exposure control methods is a method of carrying out no exposure compensation for brightness determined to be daylight and outdoor without doubt and carrying out the exposure compensation for brightness determined to be night or indoor with high possibility.
  • it is also possible to adopt a method of switching the exposure control with a slope of exposure compensation amount against brightness Even in the daylight and outdoor cases, however, the major subject can be relatively dark because of backlight, depending upon scenes.
  • auxiliary light auxiliary light
  • the photography without emission of flash light can record the atmosphere of the light source in that situation as it is, and it results in providing a photograph with more realistic atmosphere, thus enabling natural photography while the photographer and subject both are not excessively conscious of the camera. It is, however, preferable to equip the camera with a function of emitting a warning signal of underexposure to the photographer to encourage use of auxiliary light, in the region of not more than the system sensitivity.
  • Fig. 8 is a flowchart showing the control processing in the automatic photography mode of the camera according to the present embodiment.
  • the camera of the present embodiment performs characteristic operations as described below as to exposure setting and emission of flash.
  • the automatic mode is an initial operation mode upon application of power, and the display 50 provides a mode display of "AUTO.”
  • the control processing shown in Fig. 8 is started according to the film speed of the loaded film.
  • the first step S10 is to determine whether the remaining level of the battery 61 is not less than a predetermined value.
  • the display When the remaining level of the battery 61 is less than the predetermined value, the display provides a battery exhaustion display or the like (S12) , and the control processing is terminated.
  • the calculation of Bv value is carried out (S14) .
  • the calculation process of Bv value is carried out by converting a measurement signal from the photometer 18 to a Bv value. Then the flow goes to SI 6 to calculate the system sensitivity Ls and to determine whether the system sensitivity Ls is not more than 3. Namely, it is determined whether the speed value Sv of the film is not more than 9.
  • the system sensitivity Ls is determined to be not more than 3.
  • the system sensitivity Ls is determined not to be not more than 3.
  • a ranging calculation is carried out (S20).
  • the ranging calculation process is a process of calculating the distance to the subject on the basis of an output signal from the light receiver 16.
  • the flow goes to S30 to determine whether the shutter speed is longer than 1/30 [second] .
  • the flow moves to S34.
  • the shutter speed is set to 1/30 [second] (S32) and the flow goes to S34.
  • S34 is to perform an AF driving process.
  • the AF driving process is a process of moving a focusing lens according to the distance to the subject.
  • the controller 20 outputs a drive control signal to a focus driving section (not shown) and the focusing lens is moved to be focused at the distance to the subject, thus achieving focus adjustment.
  • the flow goes to S36 to perform a shutter opening operation and to perform emission of light (flash emission) under predetermined conditions. Then the flow moves to S58.
  • the flash unit (strobe) is activated under conditions that the exposure amount with flash becomes correct, except for a case where the photometric luminance value is not less than Bv 5 (i.e.
  • the photographic environment is recognized as a daytime and outdoor scene, and the flow goes to S20.
  • the photographic environment is recognized as an indoor scene or as an evening or night outdoor scene, and the flow goes to S40.
  • S40 is to perform a ranging calculation.
  • the ranging calculation process is a process of calculating the distance to the subject, based on an output signal from the light receiver 16.
  • ⁇ Ev is an exposure compensation amount and is set based on the Bv value.
  • an exposure control table of correspondence between Bv and ⁇ Ev is preliminarily set, and ⁇ Ev is determined based on this exposure control table.
  • the Bv value falls in the range of 1 to 5 [EV]
  • ⁇ Ev is set at +3 [EV] .
  • the Ev value is calculated using the ⁇ Ev thus set.
  • the flow goes to S44 in Fig. 8 to calculate the f-number and the shutter speed based on the Ev value.
  • This calculation process is carried out, for example, by preliminarily storing an exposure program chart as shown in Fig. 10, in the controller 20 or in the external memory 62 and by determining the f-number and shutter speed based on the exposure program chart. Then the flow goes to S46 to determine whether the Bv value is smaller than the system sensitivity. When the Bv value is determined not to be smaller than the system sensitivity, the flow goes to S50. It is determined on the other hand that the Bv value is smaller than the system sensitivity, a warning process is carried out.
  • the warning process is a process of issuing a warning of underexposure, and is carried out, for example, by blinking the warning indicator 42 and a predetermined mark on the display 50 on and off.
  • the flow goes to S50 to determine whether the shutter speed is longer than 1/30 [second] .
  • the flow goes to S54.
  • the shutter speed is set to 1/30 [second] (S52) and the flow goes to S54.
  • S54 is to perform an AF driving process.
  • the AF driving process is a process of moving the focusing lens according to the distance to the subject.
  • the controller 20 outputs a drive control signal to the focus driving section (not shown) and the focusing lens is moved so as to be focused at the distance to the subject, thus achieving focus adjustment.
  • S18 the judgment whether the Bv value is less than 5
  • S36 or S56 the shutter opening operation
  • the photography is carried out without emission of flash, where the photometric value is less than Bv 5 (i.e. L-value of 10) .
  • the exposure value is so set that the shutter speed is not smaller than 1/30 [second], which is the hand-shake control shutter speed.
  • the aperture is fixed to F2.0 and the shutter speed to 1/30 [seconds] .
  • the warning indicator 42 and a predetermined icon on the display 50 are blinked on and off to encourage the photographer to perform an operation of switching the mode into the flash emission mode.
  • the display 50 provides a display of natural photography mark 51d.
  • This lens returning operation is a process of returning the focusing lens to a predetermined standby position.
  • the controller 20 outputs a drive control signal to the focus driving section (not shown) to carry out the process.
  • a film frame feed is carried out (S60) and the camera goes into a standby state (S62) .
  • the exposure compensation amount may be any other value than +3 EV as long as the exposure compensation is not less than +1.5 EV. Operations in the other photograph modes will be described below.
  • an exposure program in a forced flash emission mode is the same as that in the aforementioned automatic photography mode, but the flash unit is activated under such control as to achieve an exposure amount according to ranging information.
  • the exposure is kept at the same exposure compensation amount of +3 EV as in the automatic mode, and the exposure is done with flash in intensity correct for ISO 1600.
  • the exposure and flash light quantity are the same as those in the forced flash emission mode and a single or a plurality of pre-emissions are given in an emission quantity lower than that in the photography before opening of the shutter, in order to prevent the red-eye phenomenon with flash emission.
  • an exposure program is the same as that in the red-eye prevention mode except for release of the hand-shake control.
  • a well-known color temperature detecting sensor unit may be additionally mounted on the front surface of the camera and the camera is configured so that in the operation in the automatic mode where the film with the film speed not less than 1600 (in the ISO speed) is loaded, the exposure compensation amount is set to +2 EV at color temperatures of not less than 3800K and to +3 EV at color temperatures of less than 3800K.
  • the shutter speed when compared with the first embodiment, can be set faster in cases where the color temperature is not less than 3800K, which provides an effect of further reducing the frequency of hand-shakes and shakes of moving bodies.
  • Industrial Applicability A photographer can take a photograph with good atmosphere automatically without use of such an auxiliary light as a flash light.

Abstract

A film-loading type camera comprises an exposure setting unit setting an exposure condition. The exposure setting unit carries out an exposure compensation of not less than +1.5 EV for a photometric value when the camera is loaded with a film of a film speed with which a system sensitivity defined as Ls in the following equation is not more than a specific value: Ls = 5-log2 (S/3.125)-log2 T0 +2⋅log2 F0. In the equation, S is an arithmetic expression of the ISO speed of the loaded film, F0 is an f-number at full opening of the camera lens, and T0 is a maximum shutter speed in second.

Description

DESCRIPTION
CAMERA AND METHOD FOR SETTING EXPOSURE CONDITION OF THE SAME
Technical Field The present invention relates to a film-loading type camera in which an exposure condition is automatically set and a method for setting an exposure condition of the same. Background Art Fully automatic compact cameras are in widespread use, which automatically sets an exposure condition while requiring a user to do nothing except for loading a film and which permits the user to take a satisfactory photograph by simply depressing a shutter release button. The cameras of this type are configured to automatically perform the focus control and control of auxiliary light, as well as the exposure control, and permit everyone to take a photograph by merely powering up and releasing the shutter. Such cameras have a function of effecting correct exposure for a major subject by automatic light emission from a built-in flash unit even in scenes of dark subject such as indoor scenes and night scenes. [Patent Document 1] Japanese Patent Application Laid-Open No. 5-34754
Disclosure of the Invention The flash light presents the convenience of enabling photography in any environments as described above, but photographs taken with flash light often lack the realistic atmosphere in the scene for the following reasons: - the flash light may not reach the background to result in dark, dismal description relative to the major subject; and - the main subject is taken with light which does not exist in the scene, and thus may give an unnatural impression. There also exist cameras having a mode of enabling photography without emission of flash, but the photography in that mode had the following defects: - insufficient sensitivity results in long exposure which may induce blurring of images due to a "handshake" such as movement of a photographer;
- a person may be photographed in underexposure;
- a photograph taken under a light bulb may become yellowish in color;
- a non-flash mode needs to be set every time the power is tuned on. Japanese Patent Application Laid-Open No. 5-34754 (Patent Document 1) discloses the invention in which the film speed is set to a lower value where the subject is not more than a specific luminance. However, it has the problem that the frequency of occurrence of hand-shakes is raised and inconveniences compact-camera users liking to easily enjoy photography since the system sensitivity becomes low with a low-speed film loaded. It is therefore an object of the present invention to provide a camera capable of automatically taking a photograph with good atmosphere while being free of the aforementioned defects, even if such an auxiliary light as a flash light is not used. Specifically, a film-loading type camera of the present invention comprises an exposure setting unit setting an exposure condition to carry out an exposure compensation of not less than +1.5 EV for a photometric value when the camera is loaded with a film of a film speed with which a system sensitivity defined as Ls in the following equation is not more than a specific value : Ls = 5 - log2 (S/3.125)- log2 T0 + 2 • log2 F0 where S is an arithmetic expression of the ISO speed of the loaded film, F0 is an f-number at full opening of the camera lens, and T0 is a maximum shutter speed in second. According to the present invention, it is feasible to photograph the subject with a natural touch and to take an atmospheric photograph, even if such an auxiliary light as a flash light is not used. Preferably, in the film-loading type camera of the present invention, the exposure setting unit carries out the exposure compensation only when the photometric value is not more than a specific value. By adopting this constitution, it is feasible to diminish underexposure (insufficient exposure) of the major subject affected by illuminance of surroundings (for example, a person or people illuminated by indoor illumination) . More preferably, the exposure setting unit carries out the exposure compensation when the camera is loaded with a film of a film speed with which the system sensitivity Ls is not more than 4. By adopting this constitution, further proper exposure can be performed. Further, it is preferable that the maximum shutter speed T0 is restricted not to exceed a certain value. By adopting this constitution, it is feasible to further diminish the possibility of hand-shake effect . Further preferably, the exposure setting unit calculates the system sensitivity Ls with the upper time limit T0 of 1/30 seconds if the upper time limit To is not set to a specific value. By adopting this constitution, it is feasible to diminish the possibility of hand-shake effect even if the hand-shake control shutter speed is not set. Further, the exposure setting unit may include a photometer measuring luminance of ambient light in a photographic field; a film speed sensor detecting a film speed of the loaded film; and a controller setting the exposure condition with calculating the system sensitivity Ls by a measurement signal fxom the photometer and a detection signal from the film speed sensor in order to control opening operation of a shutter. Further, it is preferable that no auxiliary light is emitted when the exposure setting unit caπrries out the exposure compensation. By adopting this constitution, it is feasible to avoid an artificial impression of the subject. Moreover, the present invention can be described as a method for setting an exposure condition of a film-loading type camera with similar operations and effects. Specifically, according to the present invention, the method for setting an exposure condition comprises the steps of: calculating a system sensitivity defined as Ls in the following equation: Ls = 5 -log, (S/3.125)-log2 T0 + 2 -log2 F0 where S is an arithmetic expression of the ISO speed of the loaded film, F0 is an f-number at full opening of the camera lens, and T0 is a maximum shutter speed in second; and carrying out an exposure compensation of not less than +1.5 EV for a photometric value when the system sensitivity defined Ls is not more than a specific value. The present invention successfully provides a camera and a method for setting an exposure condition thereof with permitting every photographer, particularly, even an inexperienced photographer to take a photograph with good atmosphere even in indoor and evening/night scenes, without use of such an auxiliary light as a flash light. Brief Description of the Drawings Fig. 1 is a perspective view to show the appearance of a camera according to the first embodiment of the present invention. Fig. 2 is a perspective view to show the appearance of the camera according to the first embodiment of the present invention. Fig. 3 is an illustration to illustrate a display in the camera of Fig. 1. Fig. 4 is a schematic diagram to show a configuration of the camera of Fig. 1. Fig. 5 shows an example of spectral sensitivity of a silicon photodiode photometric sensor equipped with an infrared cut filter. Fig. 6 shows spectral energy distributions of tungsten light (solid line as CIE standard source A) and a light source according to daylight (dotted line as CIE standard source C) . Fig. 7 shows typical spectral sensitivities off a color negative film (solid line as a blue-sensitive layer, dotted line as a green-sensitive layer, and chain line as a red-sensitive layer) . Fig. 8 is an illustration showing an example of: a flowchart from depression of a release button to completion of photography in an automatic mode of the camera in Embodiment 1 according to the present invention. Fig. 9 is a ΔEv-Bv chart wherein a solid line indicates an exposure control in the automatic mode where a film of the ISO speed of 1600 is loaded on the camera of Embodiment 1 and wherein a dashed line indicates an exposure control in the automatic mode where a film of the ISO speed of 800 is loaded on the same camera, in which the horizontal axis represents the photometric value (Bv values, together with L- values) by centerweighted metering means and in which the vertical axis represents the exposure compensation amount ΔEv [EV] . Fig. 10 is a program chart in the automatic mode where the film of the ISO speed of 1600 is loaded on the camera of Embodiment 1 according to the present invention. The following is the description of aj or reference symbols: 10: camera body; 11: release button; 13: lens barrel; 14: light projector; 16: light receiver; 17: flash unit; 18: photometer; 19: shutter; 20: controller; 65: film speed detector; and 80: exposure setting unit.
Best Modes for Carrying Out the Invention Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The same elements will Doe denoted by the same reference symbols throughout the description of the drawings, without redundant description. It is also noted that the present invention is by no means intended to be limited to the embodiments . (First Embodiment) Fig. 1 is a perspective view showing the front- side appearance of a camera according to the first embodiment of the present invention, and Fig. 2 a perspective view showing the back-side appearance of the camera according to the embodiment. As shown in Fig. 1, the camera of the present embodiment is an application of the present invention to a lens shutter camera to be loaded with a film cartridge of the 135 film format. This camera is provided with a release button 11 at an upper end of a camera body 10. A lens barrel 13 equipped with a photographic lens 12 is mounted in the central part of the front surface of the camera body 10. The lens barrel 13 used herein is a photographic lens barrel, for example, comprised of a monofocal lens with the focal length of 24 mm and full-aperture F2.0, and a shutter and being capable of autofocus operation. There are a light projector 14, a view finder 15, a light receiver 16, and a flash unit 17 provided in the
• upper part of the camera body 10. The light projector 14 and the light receiver 16 constitute a range finder for measuring the distance to the subject, for example, based on the principle of triangulation. The camera body 10 is also provided with a photometer 18. The photometer 18 functions as a photometric means for measuring the luminance of ambient light in a photographic field. This photometer 18 is, for example, one equipped with an SPD device (incorporating an infrared cut filter on the optical path) as a centerweighted averaging metering sensor.
This SPD device is approximately directed onto the optical axis of the photographic lens optical system. A shutter 19 is incorporated on the optical axis of the photographic lens 12 inside the camera body 10. The shutter 19 includes sectors also used as diaphragm blades for determining an exposure amount necessary for the film. This shutter 19 is, for example, a two-blade lens shutter having the f-number of 2.0 (f/2.0) at full opening and the control range Ev of 2 to 16 [EV] . As shown in Fig. 2, there are a finder eyepiece window 41 and a warning indicator 42 provided in the upper part on the back side of the camera body 10. The warning indicator 42 is, for example, one having a light emitting device of a two color type of red and green. A back lid 43 is provided below the finder eyepiece window 41 and the warning indicator 42. While the back lid 43 is opened, a film cartridge is loaded into the camera body 10. A battery lid 44 is provided beside the back lid 43. While the battery lid 44 is opened, a battery is loaded into the camera body 10. The back lid 43 is provided with a main switch 45, a mode switch 46, date switches 47, and a display 50. The main switch 45 is a switch for switching the whole camera on and off. The mode switch 46 is a switch for enabling switching among photography modes of the camera. The date switches 47 are switches used for setting, correction, etc. of the date and others. The display 50 is a display means for displaying a selected photography mode of the camera, the date, the number of remaining frames of the film, and so on. This display 50 is, for example, an LCD. Fig. 3 shows an enlarged view of the display 50. As shown in Fig. 3, the display 50 is provided, for example, with a photography mode display 51, a date display 52, and a number-of-frames display 53. The photography mode display 51 is a portion for displaying a photography mode selected and includes an autophotography mark 51a, a flash photography mark 51b, a non-flash photography mark 51c, and a natural photography mark 51d. The date display 52 is a part for displaying the date, for example. The number-of- frames display 53 is a part for displaying the number of remaining frames of the film. Fig. 3 shows the display 50 in which all the marks and others are in a displayed state. During use of the camera, the display 50 provides indications according to a selected photography mode, the date, and the number of frames. Fig. 4 is a block diagram schematically showing an electric configuration of the camera according to the present embodiment. As shown in Fig. 4, the camera of the present embodiment is provided with a controller 20. The controller 20 performs the control of the entire camera and includes, for example, a CPU, a ROM, a RAM, an input signal circuit, an output signal circuit, and so on. The ROM of the controller 20 stores programs for control processing and arithmetic processing. The RAM of the controller 20 stores various data used in the control processing and arithmetic processing. In the camera of the present embodiment, the photometer 18, the shutter 19 and this controller 20 are the minimum elements for constituting an exposure setting unit 80 to set an exposure condition, which will be described later. The display 50 is connected to the controller 20. The display 50 provides indications of a selected photography mode, the date, the number of remaining frames of the film, etc. in accordance with a display control signal from the controller 20. The main switch 45, the mode switch 46, and the date switches 47 are connected to the controller 20. The controller 20 powers the camera on and off in response to input at the main switch 45. The controller 20 sets or changes the photography mode in response to input at the mode switch 46. The controller 20 also sets or changes the date and others in response to input at the date switches 47. The light projector 14 and the light receiver 16 constitute a ranging calculation unit, and each of them is connected to the controller 20. The controller 20 outputs an emission control signal to the light projector 14 to perform a light projection control. The controller 20 makes the light receiver 16 receive reflected light of the projected light, and detects a distance to a subject, based on the received light signal. The flash unit 17 is connected to the controller 20. The controller 20 outputs an emission control signal to the flash unit 17 under predetermined conditions to make the flash unit emit light. The photometer 18 is connected to the controller 20. The controller 20 receives a measurement signal from the photometer 18 and converts the luminance of ambient light to a Bv value of the APEX (Additive System of Photographic Exposure) unit. The shutter 19 is connected to the controller 20. The controller 20 makes the shutter 19 perform an opening operation according to an exposure control when the release button 11 is depressed. The battery 61 is connected to the controller 20.
The battery 61 is a power supply for supplying power to each part of the camera. The controller 20 determines whether the battery 61 stores the amount of electricity enough for the photographic operation and others. An external memory 62 is connected to the controller 20. The external memory 62 stores various control parameters and others. The external memory 62 is, for example, an EEPROM. A release switch 63 is connected to the controller 20. The release switch 63 is a switch to be changed over with depression of the release button 11. With input of the release switch 63 the controller 20 determines that the release button 11 was depressed. A date copier 64 is connected to the controller 20. The date copier 64 is a copy mechanism for copying the date and others onto the film. Furthermore, a film speed sensor 65 is connected to the controller 20, and the controller 20 receives a detection signal from the film speed sensor 65. The film speed sensor 65 is a film speed detecting means for detecting a film speed of the film loaded in the camera body 10. For example, the film speed sensor 65 reads the CAS code indicated on the cartridge containing the film, to detect the film speed. Namely, the film speed sensor 65 has four conducting terminals (one of which is a common terminal) for reading the upper three bits inside the film cartridge chamber. The upper three bits indicate the speed value of one step unit out of the CAS codes printed in a checkered pattern on the side face of the film cartridge. The film speed sensor 65 also has a film speed setting mechanism of recognizing and setting the film speed by the CPU built in the camera on the basis of conduction signals from the terminals. In cases where there are no CAS codes or where a reading error occurs, the film speed is set to the speed of 100. The film speed is detected as an ISO (International Organization for Standardization) speed. Next, the system sensitivity of the camera will be described. In the present invention, the brightness of each scene will be indicated by an L-value in conformity with the APEX system. The L-value is defined as follows using an opening time value Tv and an aperture value Av of the lens to achieve proper exposure in use of a photographic sensitive material of the ISO speed of 100. L=Tv+Av In the above equation, the opening time value Tv is defined by: Tv = -log2Ss (where Ss is shutter speed [second]), and the aperture value Av is defined by: Av=21ogFn (where Fn is f-number) . For the definition of the aperture value Av, the f- nu ber of the stop of the lens is used. The system sensitivity Ls is defined as a minimum L-value of brightness enabling photography without hand-shakes, and is expressed by the equation below, using the maximum shutter speed T0 of the camera and the f-number F0 at full opening of the camera lens, and the ISO speed (arithmetic expression) S of the sensitive material loaded. Ls = 5-log2(s/3.125)-log2T0+2-log2F0 In the above equation, if the upper limit of shutter speed (opening time of the shutter) is restricted not to exceed a certain value (this value will also be called a "hand-shake control shutter speed") , the maximum shutter speed T0 is set to the hand-shake control shutter speed. If the hand-shake control shutter speed is not set, the upper time limit may be assumed to be 1/30 [second] for calculation. The constant of 5 in the above equation is an Sv value (a speed expression by the APEX system) corresponding to the sensitive material of the ISO speed of 100. The camera of the present embodiment is preferably provided with the hand-shake control shutter speed. It is generally assumed that few hand-shakes occur if the time is shorter than (1/focal length [mm] ) [second] on the 135 format basis. Therefore, the upper time limit can be determined in conformity with this assumption. Since the probability of occurrence of hand-shakes can be decreased as the shutter speed becomes faster, it is preferable to set the shutter speed as fast as possible in consideration of the necessary system sensitivity. According to the above definition of Ls, correct exposure can be made if the brightness of a scene is not less than the system sensitivity. If the brightness of a scene is not more than the system sensitivity, correct exposure will not be made and the exposure will be underexposure. The film speed can be acquired in such a way that the cameras reads the speed information described on the film cartridge. In the 135 film format, the film speed code called the CAS code is ndicated by five bits of either conduction or insulation of electric contacts on the cartridge, and the camera can read the information. The term "a specific system sensitivity can be implemented" means that the system sensitivity calculated by the camera-controllable full-aperture diaphragm stop and hand-shake control shutter speed, and the film speed of the loaded film is not more than a certain value. Namely, a threshold is prepared on the camera side and, if a system sensitivity becomes not more than the threshold, "a specific system sensitivity can be implemented." The system sensitivity Ls for exposure control of the present invention may be any value, but preferably Ls ≤ 4, and more preferably Ls ≤ 3. Next, the exposure compensation of the camera will be described. In 80% or more of indoor photography cases, which relates to one of purposes of the present invention, the major subject is a person or people illuminated by indoor illumination. If under such circumstances correct exposure is calculated based on a photometric value obtained by photometry of the camera, particularly, by the centerweighted averaging metering often used in the compact cameras, the major subject will be photographed in underexposure and will result in a dark, dismal photograph. The photometric value stated herein is brightness of a scene measured by the photometric means of the camera and is indicated as a luminance value Bv according to the APEX system (the L-value is given by "Bv + 5") . Namely, the "correct exposure based on the photometric value" refers to exposure under a condition satisfying Ev(= Tv + Av) = Bv + Sv, where Bv is the photometric value and Sv is the speed value of film. The inventors found that the above-described problem was caused by the following factors. 1) The brightness of the major subject is about 1-3 EV darker than the photometric value of the camera. 2) There exist light sources whose blue component is about 1-2 EV lower than the spectral sensitivity used in photometry in cameras. The cause of the above-mentioned phenomenon 1) lies in the fact that the indoor illumination is mainly illumination from the ceiling and is designed on the basis of the horizontal illuminance and illuminance near the wall, and little consideration is given to the illuminance on the vertical plane near the center of the room. According to the research by the inventors, the illuminance on the vertical plane near the center is about 1-3 EV darker than that near the wall. Since the photometric value of the camera, particularly, the photometric value by the centerweighted averaging metering is largely affected by the illuminance on the wall surface, the exposure control based on the raw photometric value of the camera results in underexposure (insufficient exposure) of about 1-3 EV for the major subject. The above-mentioned phenomenon 2) occurs under illumination of low color temperature, e.g., under tungsten lamps and fluorescent lamps in bulb color. Fig. 5 is a diagram showing typical spectral sensitivity of SPD photometer (with infrared cut filter) . The photometry of the camera is performed with a photometric sensor with the spectral sensitivity range near 500-600 nm as shown in Fig. 5 (the photometric sensors widely used include CdS cells or silicon photodiodes (SPDs) with an infrared cut filter) . On the other hand, Fig. 6 is a diagram showing spectral examples of light sources. The energy distribution of the CIE standard source A (correlated color temperature: about 2850K) , which is a typical tungsten light source, has a slope against wavelength, as indicated by a solid line in Fig. 6, and the energy in the region of 400-500 nm is lower than in the region of 500-600 nm. The typical spectral sensitivities of a color negative film are as shown in Fig. 7. In fig. 7, an example of spectral sensitivities of the color negative film is normalized as max = 1.
Figure imgf000022_0001
In this integration, λ is the wavelength [nm] ,
Si (λ) the spectral sensitivity of the negative film at the wavelength λ (i = 0, 1, or 2 for the red-sensitive layer, the green-sensitive layer, or the blue-sensitive layer, respectively), R(λ) the reflectivity of the object at the wavelength λ, and E (λ) the spectral energy of the light source at the wavelength λ. The integral value calculated by this integration is an exposure amount for the color negative film. In the ordinary daylight case (correlated color temperature: about 5000K) , exposure values are at the same level for the green-sensitive layer and the blue- sensitive layer close to the spectral sensitivity of the photometric sensor, but in the tungsten light case, the exposure amount for the blue-sensitive layer becomes 1-2 EV lower than that for the green-sensitive layer. This phenomenon lies in the fact that the spectrum thereof is substantially in the green light region although an ordinary photometric sensor is designed based on the spectral sensitivity of human eyes, i.e., based on the spectral sensitivity according to the standard luminous efficiency. For example, let us suppose that two types of light sources shown in Fig. 6 (the CIE standard source
A and standard source C) are adjusted in intensity (illuminance) thereof so that the photometric sensor with the spectral sensitivity shown in Fig. 5 provides the same photometric value and that a color negative film for daylight with the spectral sensitivities shown in Fig. 7 is exposed to their light. Theoretically, in comparison with the case where the film is exposed to the light from the light source C with the spectral distribution close to the daylight balance, the exposure amount for the green-sensitive layer demonstrates little change (decrease of Δ0.02 EV) but the exposure amount for the blue-sensitive layer does the decrease of 1.56 EV (while the exposure amount for the red-sensitive layer shows the increase of 0.88 EV) in the case of the light source A of the lower color temperature . As described above, the major subject is darker than the photometric value of the camera in many cases and the present invention has solved this problem by the exposure compensation of not less than +1.5 EV for the photometric value. The "exposure compensation of +ΔEv [EV] " means a correction satisfying: Ev=Bv+Sv-ΔEv. The exposure compensation breadth of +1.5 EV is a minimum correction amount, and the exposure compensation is preferably not less than +2 EV and more preferably not less than +3 EV. The magnitude of the exposure compensation may be further corrected using information except for the photometric value. For example, where a sensor to detect color temperature is available, the exposure compensation breadth can be corrected according to the color temperature measured. For example, a preferred correction is such that the exposure compensation is +3 EV at 3000K and +2 EV at 5000K. The exposure compensation method may be any method that can increase the exposure amount as a result. It may be a method of adding an exposure compensation value to the photometric value and feeding the result to an arithmetic circuit of exposure control, or a program for this exposure control may be preliminarily defined as a table against photometric values. Another method may be to perform a calculation using a result of subtraction of a desired exposure compensation amount from the film speed. In the exposure compensation of the present invention, it is preferable to change on/off of the exposure compensation and the level of the exposure compensation in accordance with brightness of the subject. The purpose of the exposure compensation is to correct the influence of artificial illumination in the indoor and other circumstances, and no exposure compensation is needed under circumstances clearly different from the artificial illumination. One of preferred exposure control methods is a method of carrying out no exposure compensation for brightness determined to be daylight and outdoor without doubt and carrying out the exposure compensation for brightness determined to be night or indoor with high possibility. For example, this reference brightness can be set to be the L-value of 10 (this brightness corresponds to the photometric value of Bv = 5) . Instead of suddenly switching the exposure control at the L-value of 10, it is also possible to adopt a method of switching the exposure control with a slope of exposure compensation amount against brightness . Even in the daylight and outdoor cases, however, the major subject can be relatively dark because of backlight, depending upon scenes. Since in the daylight and outdoor cases the level of loss of the atmosphere due to flash emission is low, it is preferable to picture the major subject with emission of flash. At the night or indoors, it is preferable not to automatically emit flash light (i.e. auxiliary light) in a region where the exposure compensation of the present invention is effected. The photography without emission of flash light can record the atmosphere of the light source in that situation as it is, and it results in providing a photograph with more realistic atmosphere, thus enabling natural photography while the photographer and subject both are not excessively conscious of the camera. It is, however, preferable to equip the camera with a function of emitting a warning signal of underexposure to the photographer to encourage use of auxiliary light, in the region of not more than the system sensitivity. Next, the operation of the camera of the present embodiment will be described. Fig. 8 is a flowchart showing the control processing in the automatic photography mode of the camera according to the present embodiment. The camera of the present embodiment performs characteristic operations as described below as to exposure setting and emission of flash. When a user loads a film on the camera and turns power on, the camera becomes ready for photography in the automatic mode. The automatic mode is an initial operation mode upon application of power, and the display 50 provides a mode display of "AUTO." When in this standby state in the automatic photography mode the photographer depresses the release button, the control processing shown in Fig. 8 is started according to the film speed of the loaded film. The first step S10 is to determine whether the remaining level of the battery 61 is not less than a predetermined value. When the remaining level of the battery 61 is less than the predetermined value, the display provides a battery exhaustion display or the like (S12) , and the control processing is terminated. On the other hand, when the remaining level of the battery 61 is not less than the predetermined value, the calculation of Bv value is carried out (S14) . The calculation process of Bv value is carried out by converting a measurement signal from the photometer 18 to a Bv value. Then the flow goes to SI 6 to calculate the system sensitivity Ls and to determine whether the system sensitivity Ls is not more than 3. Namely, it is determined whether the speed value Sv of the film is not more than 9. For example, when the ISO speed of the loaded film is 1600 (Sv 9) , this camera satisfies the system sensitivity Ls of 3. Therefore, when the film of the ISO speed of 1600 or over is loaded, the system sensitivity Ls is determined to be not more than 3. When the film of the ISO speed of less than 1600 is loaded, the system sensitivity Ls is determined not to be not more than 3. Hereinafter, the case where the system sensitivity Ls is determined to be more than 3 at SI 6 is described. When it is determined at S16 that the system sensitivity Ls is more than 3, a ranging calculation is carried out (S20). The ranging calculation process is a process of calculating the distance to the subject on the basis of an output signal from the light receiver 16. Then the flow moves to S22 to carry out an exposure calculation. The exposure calculation process is a process of calculating the EV value and is executed according to the arithmetic expression of: Ev=Bv+Sv. Then the flow moves to S24 to determine whether the Ev value is not less than 16. When the Ev value is determined to be not less than 16, 16 is set as the Ev value (S26) and then the flow moves to S28. On the other hand, when it is determined at S24 that the Ev value is less than 16, the flow goes directly to S28. At S28, the f-number and the shutter speed are calculated based on the Ev value. This calculation process is carried out, for example, based on an exposure program chart stored in the controller 20 or in the external memory 62. Then the flow goes to S30 to determine whether the shutter speed is longer than 1/30 [second] . When it is determined that the shutter speed is not longer than 1/30 [second] , the flow moves to S34. When it is determined on the other hand that the shutter speed is longer than 1/30 [second], the shutter speed is set to 1/30 [second] (S32) and the flow goes to S34. S34 is to perform an AF driving process. The AF driving process is a process of moving a focusing lens according to the distance to the subject. For example, the controller 20 outputs a drive control signal to a focus driving section (not shown) and the focusing lens is moved to be focused at the distance to the subject, thus achieving focus adjustment. Then the flow goes to S36 to perform a shutter opening operation and to perform emission of light (flash emission) under predetermined conditions. Then the flow moves to S58. When the film not satisfying the predetermined system sensitivity is loaded, as described above, the exposure control is carried out so that correct exposure is achieved in the correction that the shutter speed is not more than 1/30 [second], which is the hand-shake control shutter speed, in the control range of the shutter. Namely, the exposure calculation process is executed according to the arithmetic expression of: Ev(=Av+Tv)=Bv+Sv . The flash unit (strobe) is activated under conditions that the exposure amount with flash becomes correct, except for a case where the photometric luminance value is not less than Bv 5 (i.e. L-value of 10) and where the result of ranging is greater than 10 m. The operation herein is a well-known mode and corresponds, for example, to the "AUTO" mode of the compact camera "FUJIFILM Silvi F2.8" manufactured by FUJINON CORP. An example of the exposure control with the film of ISO 800 being loaded is indicated by a dashed line in the ΔEv-Bv chart of Fig. 9. Next, the case where the system sensitivity Ls is determined to be not more than 3 at S16 is described. When it is determined at S16 that the system sensitivity Ls is not more than 3, it is determined whether the Bv value is less than 5 (S18) . When the Bv value is determined not to be less than 5, the photographic environment is recognized as a daytime and outdoor scene, and the flow goes to S20. On the other hand, when it is determined at SI 8 that the Bv value is less than 5, the photographic environment is recognized as an indoor scene or as an evening or night outdoor scene, and the flow goes to S40. S40 is to perform a ranging calculation. The ranging calculation process is a process of calculating the distance to the subject, based on an output signal from the light receiver 16. Then the flow goes to S42 to perform an exposure calculation. The exposure calculation process is a process of calculating the Ev value, and is executed according to the arithmetic expression of: Ev=Bv+Sv-ΔEv. In the above arithmetic expression, ΔEv is an exposure compensation amount and is set based on the Bv value. For example, as indicated by a solid line in Fig. 9, an exposure control table of correspondence between Bv and ΔEv is preliminarily set, and ΔEv is determined based on this exposure control table. Specifically, where the Bv value falls in the range of 1 to 5 [EV] , ΔEv is set at +3 [EV] . Then the Ev value is calculated using the ΔEv thus set. Then the flow goes to S44 in Fig. 8 to calculate the f-number and the shutter speed based on the Ev value. This calculation process is carried out, for example, by preliminarily storing an exposure program chart as shown in Fig. 10, in the controller 20 or in the external memory 62 and by determining the f-number and shutter speed based on the exposure program chart. Then the flow goes to S46 to determine whether the Bv value is smaller than the system sensitivity. When the Bv value is determined not to be smaller than the system sensitivity, the flow goes to S50. It is determined on the other hand that the Bv value is smaller than the system sensitivity, a warning process is carried out. The warning process is a process of issuing a warning of underexposure, and is carried out, for example, by blinking the warning indicator 42 and a predetermined mark on the display 50 on and off. Then the flow goes to S50 to determine whether the shutter speed is longer than 1/30 [second] . When the shutter speed is determined not to be longer than 1/30 [second], the flow goes to S54. When it is determined on the other hand that the shutter speed is longer than 1/30 [second] , the shutter speed is set to 1/30 [second] (S52) and the flow goes to S54. S54 is to perform an AF driving process. The AF driving process is a process of moving the focusing lens according to the distance to the subject. For example, the controller 20 outputs a drive control signal to the focus driving section (not shown) and the focusing lens is moved so as to be focused at the distance to the subject, thus achieving focus adjustment. Then the flow goes to S56 to perform a shutter opening operation without emission of flash. The following is the summary how the camera according to the present embodiment operates in the steps from S18 (the judgment whether the Bv value is less than 5) to S36 or S56 (the shutter opening operation) . When the film satisfying the predetermined system sensitivity is loaded, as described above, the photography using available light is carried out with the exposure compensation of +3 EV, i.e., under the condition of: Ev=Bv+Sv~3. In this case, the photography is carried out without emission of flash, where the photometric value is less than Bv 5 (i.e. L-value of 10) . However, the exposure value is so set that the shutter speed is not smaller than 1/30 [second], which is the hand-shake control shutter speed. Therefore, for example, when the photometric value is not more than Bv 1 (i.e. L- value of 6) in the state in which the film of ISO 1600 is loaded, the aperture is fixed to F2.0 and the shutter speed to 1/30 [seconds] . When the photometric value is less than the L-value of 3 (Bv < -2) being the system sensitivity, the warning indicator 42 and a predetermined icon on the display 50 are blinked on and off to encourage the photographer to perform an operation of switching the mode into the flash emission mode. In this photographic mode, the display 50 provides a display of natural photography mark 51d. On the other hand, when the Bv value is not less than 5, the exposure control is carried out to effect correct exposure for the photometric value up to the control limit of the shutter; i.e., the exposure control satisfying the following arithmetic expression is carried out: Ev(= Av+Tv)=Bv+Sv . However, where the Ev value exceeds the control limit of the shutter (Ev > 16 in the camera of this embodiment) , the control is carried out by setting the Ev value at the control limit. (Ev = 16 in the camera of the present embodiment) After S36 or S56 (the shutter opening operation) , the flow goes to S58 in Fig. 8 to perform a lens returning operation. This lens returning operation is a process of returning the focusing lens to a predetermined standby position. For example, the controller 20 outputs a drive control signal to the focus driving section (not shown) to carry out the process. Then a film frame feed is carried out (S60) and the camera goes into a standby state (S62) . By adopting the configuration wherein when the film of a film speed with which the system sensitivity becomes not more than the specific value is loaded on the camera, the exposure compensation of +3 EV is executed for the photometric value without emission of flash, as described above, it is feasible to photograph the subject with a natural touch and to automatically take an atmospheric photograph. For example, the photography inside a room is conducted without emission of flash, and it is thus feasible to avoid an artificial impression of the subject. It is also feasible to prevent yellowish photography of the subject under illumination by a lamp bulb. In the photography of night scenes or the like, it is feasible to prevent the dark, dismal description of the background relative to the major subject due to short of flash light. It is also feasible to prevent underexposure of a person in cases where the luminance of the background is high. In such cases, the exposure compensation amount may be any other value than +3 EV as long as the exposure compensation is not less than +1.5 EV. Operations in the other photograph modes will be described below. In the camera according to the present embodiment, an exposure program in a forced flash emission mode is the same as that in the aforementioned automatic photography mode, but the flash unit is activated under such control as to achieve an exposure amount according to ranging information. Therefore, for example, supposing that the film of the ISO speed of not less than 1600 is loaded and that the photometric value is Bv 2 (i.e. LV of 7), the exposure is kept at the same exposure compensation amount of +3 EV as in the automatic mode, and the exposure is done with flash in intensity correct for ISO 1600. In a red-eye prevention mode, the exposure and flash light quantity are the same as those in the forced flash emission mode and a single or a plurality of pre-emissions are given in an emission quantity lower than that in the photography before opening of the shutter, in order to prevent the red-eye phenomenon with flash emission. In a person/night scene flash photography mode, an exposure program is the same as that in the red-eye prevention mode except for release of the hand-shake control. In a non-flash mode, photography is executed without emission of flash in any situations, as compared with that in the automatic mode. (Second Embodiment) The camera of the first embodiment described above may be modified as follows. A well-known color temperature detecting sensor unit may be additionally mounted on the front surface of the camera and the camera is configured so that in the operation in the automatic mode where the film with the film speed not less than 1600 (in the ISO speed) is loaded, the exposure compensation amount is set to +2 EV at color temperatures of not less than 3800K and to +3 EV at color temperatures of less than 3800K. In this embodiment, when compared with the first embodiment, the shutter speed can be set faster in cases where the color temperature is not less than 3800K, which provides an effect of further reducing the frequency of hand-shakes and shakes of moving bodies. Industrial Applicability A photographer can take a photograph with good atmosphere automatically without use of such an auxiliary light as a flash light.

Claims

CLAIMS 1. A film-loading type camera comprising: an exposure setting unit setting an exposure condition to carry out an exposure compensation of not less than +1.5 EV for a photometric value when the camera is loaded with a film of a film speed with which a system sensitivity defined as Ls in the following equation is not more than a specific value: Ls = 5-log2(S/3.125)-log2T0+2-log2F0 where S is an arithmetic expression of the ISO speed of the loaded film, F0 is an f-number at full opening of the camera lens, and T0 is a maximum shutter speed in second. 2. The film-loading type camera according to Claim 1, wherein the exposure setting unit carries out the exposure compensation only when the photometric value is not more than a specific value . 3. The film-loading type camera according to Claim 1 or 2, wherein the exposure setting unit carries out the exposure compensation when the camera is loaded with a film of a film speed with which the system sensitivity Ls is not more than 4. 4. The film-loading type camera according to one of Claims 1 to 3, wherein the maximum shutter speed T0 is restricted not to exceed a certain value. 5. The film-loading type camera according to one of Claims 1 to 4, wherein the exposure setting unit calculates the system sensitivity Ls with the upper time limit T0 of 1/30 seconds if the upper time limit
To is not set to a specific value. 6. The film-loading type camera according to one of
Claims 1 to 5, wherein the exposure setting unit includes : a photometer measuring luminance of ambient light in a photographic field; a film speed sensor detecting a film speed of the loaded film; and a controller setting the exposure condition with calculating the system sensitivity Ls by a measurement signal from the photometer and a detection signal from the film speed sensor in order to control opening operation of a shutter. 7. The film-loading type camera according to one of Claims 1 to 6, wherein no auxiliary light is emitted when the exposure setting unit carries out the exposure compensation. 8. A method for setting an exposure condition of a film-loading type camera, comprising the steps of: calculating a system sensitivity defined as Ls in the following equation: Ls = 5-log2(s/3.125)- log2 T0 + 2 • log2 F0 where S is an arithmetic expression of the ISO speed of the loaded film, F0 is an f-number at full opening of the camera lens, and To is a maximum shutter speed in second; and carrying out an exposure compensation of not less than +1.5 EV for a photometric value when the system sensitivity defined Ls is not more than a specific value .
PCT/JP2005/002099 2004-02-05 2005-02-04 Camera and method for setting exposure condition of the same WO2005076597A2 (en)

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