JP3563760B2 - camera - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a low-cost camera capable of performing highly accurate exposure.
[0002]
[Prior art]
In order to photograph a film with a narrow latitude, such as an instant film or a reversal film, with proper exposure, it is necessary to perform high-precision exposure adjustment with an exposure error within, for example, ±± EV to ± １ ／ EV. For this reason, a camera that performs photographing using a film with a narrow latitude requires a high-precision photometric device and an exposure device that controls the shutter speed, the aperture value, and the like with high precision.
[0003]
Further, as a low-cost camera, a camera using a single-speed shutter with a fixed aperture value, such as a film unit with a lens, is known. Some have a built-in strobe, but the light intensity is constant, relying on the latitude of the film.
[0004]
[Problems to be solved by the invention]
However, a camera equipped with a high-precision photometric device or exposure device as described above naturally has a disadvantage of increasing costs.
[0005]
Further, in the low-cost camera as described above, the exposure amount is not controlled in both cases with and without a strobe, and a wide latitude of a negative film is used. There is a problem in that a camera using a film with a narrow width cannot obtain a photograph with proper exposure.
[0006]
SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to provide a low-cost camera that can perform shooting with proper exposure even for a narrow latitude film. .
[0007]
[Means for Solving the Problems]
In order to solve the above problem, the camera of the present invention uses an instant film or a reversal film having a fixed aperture value and a shutter speed and having a smaller latitude than a negative film in a camera using a film having an ISO sensitivity of S. At the same time, when the aperture value and the shutter speed are respectively set to an aperture value F of F11 or more, and a shutter speed T (second) of 1/30 (second) or more, the following expression 2 is satisfied, and the aperture value F, ISO in the sensitivity S, photographing distance range of 1 to 3 m, a built-in auto flash dimming to provide an exposure amount in the latitude in the film, and performs photographing while operating the auto flash.
[0008]
(Equation 2)
2log ₂ F + log ₂ (1 / T) −log ₂ (S / 100)> 8
[0010]
[Action]
Generally, the brightness of a room is usually about 6 to 9 EV, and is about 11 EV even in a very bright room. For this reason, if the camera is exclusively used indoors, a shutter speed and an aperture value that will cause a large underexposure are selected, and exposure is provided by an auto strobe, even if the camera has a fixed shutter speed and an aperture value, The film can be given an exposure within the latitude. An aperture value and a shutter speed are fixed at F and T, respectively, and a camera using a film having an ISO sensitivity of S, and a subject brightness value EVa that can be properly exposed when a strobe is not used is expressed by the following equation (3).
[0011]
(Equation 3)
EVa = 2log ₂ F + log ₂ (1 / T) −log ₂ (S / 100)
[0012]
Now actually shot try to subject luminance value (e.g., luminance values of an object illuminated by indoor light) When EV _0, the difference between this and the object luminance value EVa, as follows Equation 4.
[0013]
(Equation 4)
EV ₌ EV 0 -EVa
[0014]
Within the light control range, when an auto strobe that gives an appropriate amount of exposure to a film in the dark is combined with the above-mentioned camera, the relative exposure, which is the difference between the total exposure by the strobe light and the room light, and the appropriate amount of exposure The exposure amount EVs is represented by the following Expression 5.
[0015]
(Equation 5)
EVs = log ₂ (1 + 2 ^EV )
[0016]
Assuming that the latitude is ± 0.5 EV, it is only necessary to select EVa such that | EVs | <0.5. By transforming Equation 5,
2 ^EVs = 1 + 2 ^EV
2 ^EV = 2 ^EVs -1
EV = log ₂ (2 ^EVs −1) by taking the logarithm of both sides
The following equation 6 is obtained by substituting equation 4 into this.
[0017]
(Equation 6)
EV ₀ = EVa + log ₂ (2 ^EVs −1)
[0018]
Here, if EVa = 8, then EV ₀ = 6.73 when EVs = + 0.5. Therefore, if the condition of the following Expression 7 is satisfied, it is understood that the exposure amount in the latitude can be given to the film until the room brightness reaches EV 6.73.
[0019]
(Equation 7)
2log ₂ F + log ₂ (1 / T) −log ₂ (S / 100)> 8
[0020]
【Example】
In FIG. 2, a single-use instant camera embodying the present invention includes a camera body 3 having a built-in photographing mechanism and the like, and an outer case 4 for housing the same. The camera body 3 includes an auto flash device 7 (see FIG. 3) having a shutter button 5 for performing a shutter release operation, a finder 6 for visually recognizing a shooting range, a flash light emitting unit 7a, and a light receiving window 7b for light control, and an auto flash. A charging start switch 8 for charging the device 7 and a photographing opening 10 are provided.
[0021]
The charge start switch 8 is located at a position where the finger of the hand holding the camera body 3 naturally touches when the camera body 3 is held at the time of photographing, and is always charged when photographing. Further, on the upper surface of the camera body 3, there is provided an outlet 9 from which the photographed film unit 20 is discharged. The outer case 4 has a hole for exposing the operation member and the like. As is well known, the film unit 20 has a pod portion 20a containing a developing solution at an upper end portion, and a trap portion for absorbing excess developing solution at a lower end portion with an image recording portion at a center portion therebetween. Reference numeral 20b denotes a mono-sheet type film unit provided respectively.
[0022]
In FIG. 3 showing a vertical cross section of the camera body 3, the camera body 3 includes a body base 11 in which a photographing device such as a shutter mechanism is incorporated, and an outer shell of the camera body 3 which is covered from the front side of the body base 11. And a back cover 13 which engages with the main body base 11 and the front cover 12 to cover the rear side of the camera body 3.
[0023]
The main body base 11 is formed of an opaque resin, and has a light-shielding cylinder 16 that covers the imaging optical path of the optical axis 15. An aperture 16a is formed at the front of the light-shielding tube 16, and a lens holder 19 with a photographic lens 17 and shutter blades 18 mounted thereon is attached so as to cover the aperture 16a.
[0024]
The diameter (aperture value F) of the aperture 16a and the opening / closing speed (shutter speed T) of the shutter blade 18 are values satisfying the following Expression 8, and are set to, for example, F14, 1/100 (second). The aperture value F14 is selected as a value that is hardly affected by the brightness in the room, and the shutter speed 1/100 (second) is selected as a value that does not easily cause camera shake.
[0025]
(Equation 8)
2log ₂ F + log ₂ (1 / T) −log ₂ (S / 100)> 8
[0026]
Substituting F = 14, T = 1/100, and S = 800 into this equation 8,
2log ₂ F + log ₂ (1 / T) −log ₂ (S / 100) = 11.26> 8
Thus, it is understood that Expression 8 is satisfied under the conditions of the aperture value F = 14, the shutter speed T = 1/100, and the film sensitivity S = 800. The left side of Expression 8 indicates an exposure amount determined by a combination of the aperture value F, the shutter speed T, and the film sensitivity S, that is, the brightness that should be appropriate under this condition. When the indoor light is 8 EV,
8-11.26 = -3.26EV
As a result, the exposure becomes insufficient by 3.26 EV. Therefore, this may be supplemented by strobe light. If the distance to the subject is within the light control range of the auto strobe device 7, the relative exposure to the appropriate exposure is
log ₂ (1 + 2 ^−3.26 ) = 0.14 EV
This value substantially falls within the latitude (for example, ± 0.3 EV) of the film unit 20.
[0027]
In FIG. 1, a straight line A indicates an exposure amount only by room light, and a curve B indicates a combined exposure amount by strobe light and room light. As can be seen from this figure, when the room brightness is about 9.1 EV or less, the exposure is within the latitude of the film unit 20, ± 0.3 EV. That is, when the room brightness is about 9.1 EV or less, the difference between the exposure amount that should be appropriate without strobe light and the room brightness is 11.26-9.1 = 2.16 EV or more. This value indicates that the film unit 20 having a small latitude is underexposed so large that an image cannot be formed clearly. Since this is compensated for by the adjusted flash light, it is possible to shoot with an appropriate exposure even when the aperture and shutter speed are fixed. The auto strobe device 7 uses a film having a sensitivity of ISO 800, and performs light control so as to obtain an appropriate exposure within a normal photographing distance range, for example, in the darkness of 1 to 3 m, with an aperture value of F14.
[0028]
A film unit storage chamber 21 for accommodating a plurality of film units 20 having a sensitivity of, for example, ISO800 is provided integrally with the main body base 11 in connection with the light shielding tube 16. The film unit storage chamber 21 directly stores the film unit 20 without using a film pack, and includes a receiving surface 22 that is in contact with the outside of the exposure range of the film unit 20 at a connection portion with the light shielding tube 16, and a film unit 20. And an aperture 23 for determining an exposure range of the light.
[0029]
A discharge port 25 for discharging the photographed film unit 20 is provided on the upper surface of the film unit storage chamber 21, and the film unit 20 is sandwiched and discharged at a further upper portion of the discharge port 25. Deploying rollers 26a and 26b are arranged to cleave the portion 20a to spread the developing solution on the exposed surface. Gears 27a and 27b are fixed to one ends of the developing rollers 26a and 26b, and the gears are meshed with each other. A large-diameter gear 28 is fixed to the gear 27a, and a driving gear connected to a motor 29 disposed below the light-shielding cylinder 16 meshes. Further, a film passage 30 provided integrally with the front cover 12 is disposed above the developing rollers 26a and 26b, and the film passage 30 is connected to the discharge port 9 described above. Then, the film unit 20 is discharged outside through the discharge port 25 of the film unit storage chamber 21 and the developing rollers 26a and 26b, the film passage 30 and the discharge port 9 of the camera body 3.
[0030]
The front cover 12 is formed of an opaque resin, and is provided with holes for exposing the above-described strobe light emitting portion 7a, light receiving window 7b, shutter button 5, finder 6, and the like. The motor 29 described above and a printed circuit board 32 provided with a drive circuit for driving the motor 29 are arranged in a space formed below the light shielding tube 16 when the front cover 12 is put on the main body base 11. ing.
[0031]
The back cover 13 is attached to the back side of the main body base 11 to shield the film unit storage room 21 from light. In this attachment, the projections 13a and 13b provided on the upper and lower portions inside the back cover 13 are engaged with the holes 11a and 11b of the main body base 11, and the outer periphery is fixed by ultrasonic welding. Further, a metal pressure plate 34 is attached to the inside of the back cover 13 and enters the film unit storage chamber 21 to press the film unit 20 from the back side. The pressure plate 34 is detachably engaged with claws 35a and 35b formed on the back cover 13 and is reusable.
[0032]
The single use instant camera configured as described above is used in a room having a brightness of about 9.1 EV or less. First, the photographer holds the single-use instant camera, looks into the eyepiece finder (not shown) on the back side, and visually recognizes a subject within the light control range of the auto strobe device 7 (1 to 3 m from the camera). At this time, the charge start switch 8 is pressed by the finger of the left hand, and charging of the auto strobe device 7 is started. Thereafter, after confirming a pilot lamp (not shown) indicating the completion of charging, the shutter button 5 is pressed.
[0033]
At the same time as the strobe light is emitted from the strobe light emitting portion 7a toward the subject, the shutter blade 18 is opened. The light reflected by the subject and returned is measured by the light receiving window 7b, and the emission of the strobe light is stopped when the appropriate exposure corresponding to the aperture 16a is reached. The light that has entered the light-shielding cylinder 16 through the photographing lens 17 passes through an aperture 23 provided at the boundary between the light-shielding cylinder 16 and the film unit storage chamber 21 and reaches the exposure surface of the forefront film unit 20. I do.
[0034]
Thereafter, the motor 29 starts rotating, and drives the claw member and the developing rollers 26a and 26b via the driving gear. First, the claw member lifts up the film unit 20 and sends it between the developing rollers 26a and 26b through the discharge port 25. The film unit 20 nipped by the developing rollers 26a, 26b is pressed while being moved upward by the rotation of the developing rollers 26a, 26b, so that the pod portion 20a is torn. The developer released by the tearing of the pod portion 20a is spread on the exposed surface by the developing rollers 26a and 26b to perform development. The developer remaining after spreading on the exposed surface is absorbed by the trap portion 20b.
[0035]
The film unit 20 is further fed upward by the developing rollers 26a and 26b, and enters the discharge passage 30 above the developing roller. Then, it is discharged to the outside of the camera body 3 through the discharge port 9. At the same time as the ejection of the photographed film unit 20, the pressure plate 34 presses the film unit 20 from the back side to press the next layer of the film unit 20 against the receiving surface 22.
[0036]
Although the embodiment described above is a one-time-use type instant camera, the present invention can be applied to, for example, a lens-equipped film unit having a built-in reversal film in advance. Also, F14, 1/100 (second), and ISO800 have been cited as examples of combinations of the aperture value, shutter speed, and film sensitivity that satisfy Expression 8, but the present invention is not limited to these numerical values, and other numerical values are used. May be used. However, when the aperture value is smaller than F11, for example, when the film of ISO800 is used, the aperture value is unfavorably affected by room light. If the shutter speed is 1/30 (second) or less, camera shake is likely to occur, which is not preferable. Although the value on the right side of Equation 8 is set to 8 EV, the value is set to a larger value, for example, 10 EV, more preferably 12 EV, and the aperture value F, shutter speed T, and film sensitivity S are set so as to satisfy Equation 8. If the angle is determined, the influence of light other than the strobe light (indoor light or outside light) is further reduced. However, in this case, if the film sensitivity S is increased, the influence of room light is increased.
[0037]
【The invention's effect】
As described above in detail, according to the camera of the present invention, F11 or aperture value F, 1/30 (sec) or more shutter speed T, ISO sensitivity S _{is, 2log 2 F + log 2 (} 1 / T) - A built-in auto strobe that satisfies the condition of log ₂ (S / 100)> 8, and has an aperture value F, ISO sensitivity S, and a flash control range that is appropriate within a shooting distance range of 1 to 3 m. Since the photographing is performed while the camera is operated, the photographing can be performed only with the automatically adjusted flash light without being substantially affected by light other than the flash light. Therefore, even with a simple and low-cost camera having a fixed aperture value and a single shutter speed, it is possible to shoot with an appropriate exposure even when using an instant film or a reversal film with a narrow latitude.
[Brief description of the drawings]
FIG. 1 is a graph showing an exposure state of a single-use instant camera.
FIG. 2 is a perspective view showing the appearance of a single-use instant camera.
FIG. 3 is a cross-sectional view schematically showing an internal structure of a single-use instant camera.
[Explanation of symbols]
7 Auto Strobe Device 7a Strobe Light Emitting Unit 7b Light Receiving Window 8 Charge Start Switch 16a Aperture Opening 20 Film Unit

Claims (1)

In a camera using a film with a fixed aperture value and shutter speed and an ISO sensitivity of S,
An instant film or a reversal film having a smaller latitude than that of a negative film is used as the film, and the aperture value and the shutter speed are respectively set to an aperture value F of 11 or more, and a shutter speed T (second) of 1/30 (second) or more. when, satisfies the condition of equation 1, and the aperture value F, ISO sensitivity S, the photographing distance range of 1 to 3 m, a built-in auto flash dimming to provide an exposure amount in the latitude in the film A camera that shoots while operating the auto strobe.

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