JPH0746207B2 - Color balance density correction method in color printing - Google Patents

Description

TECHNICAL FIELD The present invention relates to a color balance density correction method in a color print used when a color original image is exposed on a color photographic light-sensitive material to obtain a full-color image. .

When a color original image is recorded as a full-color negative or positive image on a single film like normal photographic film, as in the case of color printing (eg, creating a color proof), Y version, M version, C version, BK
Including a case where an image film with color-divided light is prepared like a plate, and also includes a case where the light is reflected light obtained by irradiating an original color original with light (eg, color copy).

BACKGROUND OF THE INVENTION Generally, in color printing, exposure amount control (density control) is performed by the following method.

A. Adjust the exposure time.

B. Use filters with different densities for each color.

C. Insert a filter in the center of the lens, and adjust the exposure dose according to the ratio of the lens aperture and the area occupied by the filter.

D. Adjust the density of each color separation by combining the filter for obtaining the color separation light and the ND filter with different density. E.
Adjust the amount of light emitted from the light source.

F. Adjust the lens iris.

Of the above, the methods A, B, D, E, and F can be applied to all color prints, but the method C is effective only in color print exposure of the subtractive color mixing method.

When adjusting the color balance of a color image, in addition to the relative balance of the color development of Y, M, and C, it is also necessary to adjust the total exposure amount. For example, a method that combines both methods of C and F described above, etc. Has been done.

The method B has a drawback that it is necessary to prepare a plurality of filters having different densities for each color separation, and cannot be carried out by a printer of a type having only a single density filter.

Method C cannot be used in the case of additive color mixing type color print exposure.

With the method E, it is difficult to continuously adjust the irradiation light amount of the light source without changing the spectral distribution of light.

The method F is not a good method because it has a drawback that the lens performance changes depending on the aperture value of the lens.

On the other hand, color light-sensitive materials generally have Y, M, and
C There is a difference in the sensitivity of each layer, and in order to obtain a perfect color print, it is necessary to make corrections in response to such a difference in sensitivity due to differences in production lots.

For this reason, in the simple method of making a color block by Agfa-Gevaert, the printing magazine 1984 Vol.67-3, P.45-P.50.
According to the report, "For the photosensitive material A for exposure, for example," C- / M2.5 / Y- "
The basic color correction value is displayed as shown in the above, and it is assumed that the actual shooting is "C- / M2.5 / Y5", and the new material is displayed as "C5 / M2.5 / Y-". To take a picture instead, select "C2.5 / M
-/ Y2.5 ”, both of them are said to obtain the same finish result, and color correction is performed by the following method.

Before actually shooting, select a test original, attach a gray step wedge, attach it to the original rack, select the CC filter of the basic color correction value printed on the label of the CCN box, set it in the optical system, test exposure -Process and compare with the original, and evaluate the difference in density and hue from the original. If color deviation has occurred, remove the filter of the same color as the color being changed or switch to a filter with a lighter density. If the color filter to be removed is not used, add a complementary color filter. Color correction is performed based on the above principles, but using three color (C, M, Y) filters at the same time produces a gray color and increases the amount of exposure, which does not contribute to color correction. I don't do it, so I have to avoid it. ] Furthermore, in color printing, there is a user's preference, and color correction corresponding to this is also necessary.

[Object of the Invention] In view of the above, the present invention provides only a BGR additive color filter having one density for color correction corresponding to the sensitivity variation depending on the production lot of color photosensitive material and the color balance specified by the user. The main purpose of the present invention is to clarify a color balance density correction method that can be performed while maintaining the performance of the optical system in the best condition with a printer that does not have a color printer. An object of the present invention is to clarify a color balance density correction method capable of avoiding the influence of reciprocity law failure in a photographic light-sensitive material and easily performing color correction within an exposure time range in which the characteristics of the light-sensitive material are the best. Other purposes and benefits of the above will be clarified by the following description.

[Means for Solving the Problems] The above object of the present invention is to provide a color balance density correction method in a color printer of a type in which only a single density BGR filter is prepared in an optical system. Density of each color is obtained by combining the ND filter with a different density and the BGR filter with a fixed density for the exposure of the appropriate exposure time calculated based on the approximate center value of the appropriate density indicated by the reciprocity law failure characteristic. And calculate
Using a color photographic light-sensitive material having a standard density, compare this with the density calculated by the same method as above to calculate the standard exposure time for a proper color balance, and B. change in density for each production lot. Corrected exposure amount calculated correspondingly and displayed in advance with an index for each color photographic light-sensitive material, C. corrected exposure amount specified with an index for the density that changes corresponding to the color balance specified by the user, A color balance in color printing, characterized in that the exposure time is controlled by inputting to the automatic control device by an input device, calculating these numerical values by a calculation formula and data stored in advance in the storage part of the automatic control device, and controlling the exposure time. The density correction method is achieved.

[Examples] Next, details of the present invention will be described.

The adjustment of the exposure dose according to the present invention includes the following factors: A. reciprocity law failure characteristic of color photographic light-sensitive material, B. sensitivity variation between production lots of color photographic light-sensitive material, C. color balance specified by user, Done by Hereinafter, they will be sequentially described.

First, when A is explained, the color photographic light-sensitive material is
As is well known, the example of a direct positive color photographic light-sensitive material manufactured by the applicant of the present invention has a unique reciprocity failure characteristic, and as shown in FIG. 1, when the exposure time is about 0.2 seconds to 0.5 seconds, It is desirable to set the exposure time within this range because the density range is widest.

In this case, the color balance is set at the same time. That is, at the time of shipment from the factory, a color photographic light-sensitive material having a standard sensitivity was used, and the density was fixed and the density was fixed.
By combining with BGR filter, BGR
The standard exposure time is set by setting each exposure time in the middle of 0.2 seconds to 0.5 seconds and in the vicinity of 0.35 seconds, and designated as " _TOB , _TOG , _TOR ".

In order to cope with sensitivity variations due to differences in production lots of color photographic light-sensitive materials, the corrected exposure dose corresponding to the density change in each production lot shall be displayed as an index on the outer box cartridge, etc. at the time of shipment. It is displayed as an index and is called “D _OB , D _OG , D _OR ”.

On the other hand, with respect to the color balance designated by the user, the exposure amount corresponding to this density change can be designated by an index. This is referred to as "D _UB , D _UG , D _UR ".

The above "T _OB , T _OG , T _OR ""D _OB , D _OG , D _OR " and "D _UB , D
Each numerical value of " _UG , D _UR " is input to, for example, a so-called microcomputer of the control system, The calculation formula becomes simple exposure time is required, it is possible to adjust the relative color balance obtained T _'B, T' _G, the value of T _'R.

Next, in order to adjust the total exposure amount specified by the user without changing the color balance, first, the adjusted total exposure amount at the time of shipment (standard exposure time described above), that is, " _TOB , T
_OG , T _OR "and the exposure index specified by the user as" D _UT , The formula comprised, the total exposure amount after adjustment for by the user-specified _{"T 'OB, T' OG,} T 'OR ' to ask.

Next, the total exposure amount is calculated by the formula 2 and adjusted by the user without breaking the balance of the simple exposure time "T ' _B , T' _G , T ' _R " with the relative color balance corrected by the formula 1. In order to correspond to the total exposure amount "T ' _OB , T' _OG , T ' _OR " afterwards, The final exposure times T _B , T _G , and T _R are obtained by the following formula.

Each calculation described above is performed by a built-in so-called microcomputer or the like, and the calculated BGR exposure time is preferably realized as automatic shutter control.

The numerical values obtained by the calculation are as shown in Table 1, for example.

That is, in the case of a color photographic light-sensitive material having reciprocity law failure characteristics shown in Table 1, for example, T _OB = T _OG = T _OR =
If 0.35 seconds is set, if the sensitivity variation due to production lot is within the range of ± 0.200, that is, D _OB , D _OG , and D _OR
Within the range of 0.22 to +0.22, the exposure time can be adjusted within the range of 0.22 second to 0.55 second, and the influence of reciprocity law failure of the color photographic light-sensitive material used can be avoided.

As described above, the color balance density correction by the method of the present invention is performed by: A. a range of exposure amount (time) corresponding to the reciprocity law failure characteristic of the color photographic light-sensitive material to be used, B. correction corresponding to the sensitivity variation depending on the production lot. Exposure amount (time), C. Corrected exposure amount (time) according to the user's preference, is performed only by controlling the exposure time. Specific calculation programs can be designed in various ways. Since the value of is predictable in advance, for example, based on the value of Factor A,
If a matrix chart (numerical table) based on the numerical values of Factor B and Factor C is prepared, the corrected exposure amount (time) can be easily selected. In these charts, not only the desired exposure amount (time) that is not affected by reciprocity law failure but also the numerical value in the range that can be described may be displayed. In this case, it is preferable that the desired range is divided so that it can be visually observed.

[Effects of the Invention] According to the method of the present invention, (1) variation in sensitivity depending on production lots, color correction corresponding to user's preference, and exposure time control without being affected by reciprocity law failure of a color photographic light-sensitive material. (2) It is not necessary to change the filter or change the aperture value of the lens to correct the exposure amount, so the control is easy even when using an automatic printer. It is possible to obtain the effect that color correction can be performed in a state where the optical system is kept at the best (eg, the aperture value of the lens is kept at the best state of the lens characteristics).

Further, according to the method of the present invention, since the correction of the color balance density is performed only by adjusting the exposure time, it is used especially in the color printer of the type in which only the single density BGR filter is prepared in the optical system. Therefore, to correct the color balance density, there is no need to manually replace the filter, and moreover, the device compared to a printer that automatically controls the filter replacement and the density adjustment. There are advantages in terms of simplification and manufacturing cost.

[Brief description of drawings]

FIG. 1 is a graph showing the reciprocity law failure characteristic of a direct positive type color photographic light-sensitive material.

Claims (1)

[Claims] 1. A color balance density correction method in a color printer of a type in which only a single density BGR filter is provided in an optical system, A. The approximate center of proper density indicated by the reciprocity law failure characteristic of a color photographic light-sensitive material. The exposure of the proper exposure time calculated based on the value, ND filter with different density and B with fixed density.
Proper color calculated by combining with a GR filter to calculate the density of each color and comparing it with the density calculated by the same method as above using a color photographic light-sensitive material having a standard density. Standard exposure time of the balance, B. Corrected exposure amount calculated according to the change in density of each production lot and displayed in advance as an index for each color photographic photosensitive material, C. Corresponding to the color balance specified by the user The corrected exposure amount, in which the density that changes as a result is specified by an index, is input to the automatic control device by the input device, and these numerical values are calculated by the calculation formula and data stored in advance in the storage unit of the automatic control device. A method for correcting color balance density in a color print, comprising controlling an exposure time.