JP3030071B2 - Camera exposure control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure control device for a camera, and more particularly, to an exposure control device for a camera having a function of emitting a strobe light.

[Related Art] Conventionally, exposure control of a camera is performed based on a well-known APEX calculation formula Bv + Sv = Tv + Av (1) Gv = Av + Dv + Sv (100) -Sv (2) . Where Bv is the subject brightness, S
v is the ISO sensitivity of the film. For example, Sv (100) is the ISO sensitivity of an ISO 100 film, Tv is the shutter speed, Av is the aperture, Gv is the amount of flash light emission, and Dv is a value related to distance. And the above APEX calculation is considered to be theoretically correct, and it has been proved in the photograph taken.

However, with the recent advances in science and technology, rapid progress has been made not only in camera technology, but also in the field of film development and printing. In particular, automatic printers that perform printing are making rapid progress, and automatic printers have been introduced in most minilabs at present, so that photographs are automatically printed and labor has been almost eliminated.

Well, the technology that contributed to the advancement of automatic printers was automatic exposure compensation. Automatically, even if shooting failed, the film condition was poor, or the subject's shading, light and darkness and color balance were poor, Makes beautiful photos.

[Problems to be Solved by the Invention] However, this automatic exposure correction technique is not only good, but there is no problem in the case of a positive film because the automatic exposure correction is not involved. However, since the printing, especially the automatic exposure correction, works to bring the background, which is naturally underexposed on the film, to an appropriate level, the exposure of the main subject is overshot.

As described above, if the exposure of the camera is controlled based on the APEX calculation as in the related art, a good photograph cannot be desired by the flash photography on the negative film.

Therefore, an object of the present invention is to solve the above-mentioned problems, and to provide a camera exposure control device in which a main subject is not overexposed even when a photograph taken by flash using a negative film is printed by an automatic printer. To offer.

[Means and Actions for Solving the Problems] An exposure control device for a camera according to the present invention comprises: film sensitivity detection means for detecting film sensitivity information from a DX code provided in a film magazine; Exposure calculation means for calculating an appropriate exposure, a strobe device whose light emission amount is controlled by the output of this exposure calculation means, film latitude detection means for detecting film latitude from the DX code, and Determining means for determining whether the film is a negative film or a positive film; and correcting means for correcting the light emission amount of the strobe device based on the determination result of the determining means and the film sensitivity information. If the determination result of the determination means is a negative film, Characterized by shifting the light emission amount on the under side. Further, the exposure control device for a camera according to the present invention includes: a film sensitivity detecting means for detecting film sensitivity information; an exposure calculating means for calculating an appropriate exposure based on the film sensitivity information and the subject brightness; A strobe device whose amount is controlled, determining means for reading information provided on the film cartridge to determine whether the film is a negative film or a positive film, and, when the determination result of the determining means is a negative film, Correcting means for shifting the amount of light emission of the strobe device to the under side.

Hereinafter, the present invention will be described with reference to the illustrated embodiments. First, before describing embodiments of the present invention, the basic concept of the present invention will be described below.

Generally, the ISO sensitivity of a film is made higher than the ISO sensitivity described in the DX code in order to allow a margin for the film. However, the margin of the ISO sensitivity of this film is not always the same for all the ISO sensitivities, and at present, the margin is smaller for a high-sensitivity film. By the way, the problem that the main subject is overexposed due to the automatic exposure correction in the automatic printer is as described above, but this can be substantially limited to the case where the flash photography is performed using the negative film. Therefore, in the present invention, the DX displayed on the film magazine is first used.
The latitude of the film is read from the mode, and it is determined whether the film is a positive film or a negative film. Next, in the case of a negative film, the strobe light amount is shifted toward the under side in accordance with the ISO sensitivity of the film in consideration of automatic exposure correction. The above is the basic concept of the present invention. Next, an embodiment will be described.

FIG. 1 is a block diagram of an exposure control device for a camera showing an embodiment of the present invention. In the figure, a DX code reading means 1 has a circuit format shown in FIG. 2C described below, reads a DX code of a film, and comprises a CP detecting means 2 to a strobe light emission amount shifting means 6.
Supply to U. Then, the CPU performs various calculations and various detections to obtain information on the number of frames of the film, the ISO sensitivity, and the film latitude from the DX code.

Here, to explain the inside of the CPU, the signal obtained by the DX code reading means 1 is supplied to the ISO sensitivity detecting means 3 and the film latitude detecting means 2 forming the film sensitivity detecting means. When the film latitude is detected by the film latitude detecting means 2, the film positive / negative determining means 4 determines whether the film being used is a positive film or a negative film based on the film latitude information. Next, the exposure calculation means 5
The APEX calculation shown in the above equations (1) and (2) is performed from the ISO sensitivity information detected by the ISO sensitivity detecting means 3 to determine an appropriate exposure condition including a flash emission amount. The strobe light emission amount shifting means 6 as correction means determines only the strobe light emission amount within the proper exposure condition determined by the exposure calculation means 5 based on the film positive / negative judgment and the ISO sensitivity information.
As will be described later with reference to FIG. 3, this is a means for determining a correction amount for selectively shifting.

The strobe light emission amount determining means 7 converts the information on the strobe light emission amount supplied from the exposure control calculating means 5 from an appropriate value by a shift correction amount (see Table 1) supplied from the strobe light amount shift means 6. The light is shifted intentionally and supplied to the strobe circuit 8, and actual strobe light emission is performed. The strobe device is constituted by the strobe light emission amount determining means 7 and the strobe circuit 8.

Next, the DX code reading means 1 will be described with reference to FIGS. 2A to 2C. FIG. 2A is an external view of the film magazine 11, and a portion of the DX code printed below the surface is extracted and shown in FIG. 2B. The DX codes D1 to D12 are normally read by the circuit shown in FIG. 2C. That is, the contacts 21 and 22 are connected to the DX codes D1 to D12.
If the code read by touching
Because between 1 and 22 are shorted, V _OL = V _DC next if V _OL = 0 off region, thereby allowing reading of DX code.
In this example, the film latitude information is printed by DX codes D11 and D12 as shown in Table 1 below.

As shown in Table 1, the color positive film has a DX code of ± 1/2 or 1 ± 1 film latitude.
The color negative film and black and white film are displayed as +
Since it is displayed as 2--1 or +3 --1, DX
By reading the latitude of the code, it is possible to determine whether the film is positive or negative.

The operation of the present embodiment configured as described above will be described in detail with reference to the flowchart of FIG. 3. First, when photographing is performed, it is determined whether the film type is positive or negative (step S1). Then, in the case of a positive film, an exposure control calculation is performed according to the calculation expressions (1) and (2),
(Step S2), the exposure of the camera is controlled based on the calculation result. In the case of a negative film, it is checked whether the ISO sensitivity of the film is 1000 or more (step S3), thereby changing the shift amount of the strobe light emission amount. That is, if the value is ISO1000 or more, the shift is performed to 0.5 Ev under (step S4), and if the value is ISO1000 or less, the shift is performed to 1Ev under (step S5).

The reason why we do this is that if you look at current film technology, the ISO sensitivity of the film should be higher than the value described in the DX code for the film below ISO 1000 to give the film more room. It has become. However, it is technically difficult for a film of ISO 1000 or more to have the above-mentioned margin, but it is not without its margin.
Since the strobe light amount is under 1 Ev from the appropriate value because it is smaller than that of the film of O1000 or less, it obviously has a bad effect on the finished photo. In other words, the amount of strobe light is shifted toward the underside as far as it does not adversely affect the picture, and this depends on the ISO sensitivity of the film.

Although the present embodiment operates as described above, the above specific numerical values, for example, ISO1000, 1Ev, 0.5Ev, and the like are values conceivable based on current film circumstances and are not limited to these values.

In addition, in FIG. 3 described above, it is conceivable to read the DX code for each photographing. For example, the DX code is read only when a new film is inserted, and the content is stored in a register or the like. The present invention can be applied in a range that does not impair the gist of the present invention, such as not to cause a useless time lag during photographing.

According to the above-described embodiment, conventionally, particularly when a negative film is used, the main subject is likely to be exposed to the over side by automatic exposure correction at the time of printing in a lab, but the amount of strobe light emission is predicted in advance. Shifting to the under side improves the finish as a photograph.

[Effects of the Invention] As described above, according to the present invention, when the film used is a negative film, the amount of strobe light emission is shifted to the under side, so that a photograph taken with the negative film using the strobe light can be obtained. Even when printing is performed by an automatic printer, the main subject is not overexposed.

[Brief description of the drawings]

FIG. 1 is a block diagram of an exposure control device of a camera showing one embodiment of the present invention, FIG. 2A is an external view of a film magazine, and FIG. 2B is an enlarged view of the DX code part in FIG. 2A. FIG. 2C is a circuit diagram showing an example of the DX code reading means in FIG. 1, and FIG. 3 is a flowchart showing the operation of the present embodiment. 2 ... Film latitude detecting means 3 ... ISO sensitivity detecting means (film sensitivity detecting means) 4 ... Film positive / negative determining means (determining means) 5 ... Exposure calculating means 6 ... Strobe light emission amount shifting means (correction) Means 7… Strobe light emission amount determining means (strobe device) 8… Strobe circuit (strobe device) 11… Film magazine D1 to D12… DX code

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Claims (2)

(57) [Claims] 1. A film sensitivity detecting means for detecting film sensitivity information from a DX code provided in a film magazine; an exposure calculating means for calculating an appropriate exposure based on the film sensitivity information and a subject brightness; A strobe device whose light emission amount is controlled by an output; film latitude detecting means for detecting film latitude from the DX code; determining means for determining whether the film is a negative film or a positive film from the film latitude information; Correction means for correcting the light emission amount of the strobe device based on the determination result of the determination means and the film sensitivity information, wherein the correction means is configured to output the strobe light when the determination result of the determination means is a negative film. The exposure of the camera is characterized by shifting the light emission of the device to the under side. Out control. A film sensitivity detecting means for detecting film sensitivity information; an exposure calculating means for calculating an appropriate exposure based on the film sensitivity information and a subject brightness; and a flash device for controlling a light emission amount by an output of the exposure calculating means. And, read the information provided in the film cartridge,
Determining means for determining whether the film is a negative film or a positive film; and correcting means for shifting the light emission amount of the strobe device to the under side when the determination result of the determining means is a negative film. Characteristic camera exposure control device.