RU2022308C1 - Method for color setting of photoprinting apparatus - Google Patents

Abstract

FIELD: photographic and movie equipment. SUBSTANCE: prints of a neutral grey color are made by exposing color photographic paper, then making zonal measuring grids from produced prints. Next, zonal sensitivity strips are made with the aid of neutral-grey wedge and at least three color test negatives. EFFECT: higher efficiency. 1 dwg

Description

 The invention relates to film technology, in particular to methods for color adjustment of photographic printing devices.

 A known method of visual comparison of test photo prints with the original color scale, in which visually compare the accuracy of reproduced colors and, if necessary, adjust the exposure conditions [1]. The method does not allow to quantify color reproduction and therefore involves the manufacture of several samples, which is a disadvantage.

 A known method for determining the optimal exposure conditions for color printers, which provides for a special device to obtain eight test prints, a device for measuring these prints, comparing the results with reference values and calculating correction levels using a special algorithm [2]. The disadvantage of this method is the presence of a special device that provides a change in zonal exposures to obtain eight samples, as well as a reflective densitometer for measuring densities.

 The closest in technical essence to the invention is a color adjustment method in which the color balance of photo paper and printed negative is determined in the following sequence: first, three-fold exposure of individual sections of a sheet of photo paper is carried out through a neutral-gray optical wedge with a linear continuous density gradient, each exposure is carried out with the light of the corresponding spectral composition, a given brightness and time, then chemical-photographic processing of a sheet of photo paper is carried out to radiation of three zone sensitograms (yellow, magenta, and cyan) and conduct densitometric measurements in such a way as to obtain quantitative data on the relative photosensitivity of each emulsion layer; quantitatively, photosensitivity is expressed in units of exposure time for blue, green, and red filters with additive photo printing [3]. The optical density measured by the densitometer on the corresponding sensitogram and behind the corresponding light filter is taken as a criterion of relative photosensitive. At the same time, the densitometer readings behind the blue, green, and red filters should match. The obtained data on the balance of the relative photosensitivity of photo paper are summed up with the data on the photosensitivity balance of the printed negative, which is determined using a color analyzer by measuring the "gray" field of the negative.

 The disadvantage of this method is the low accuracy of the color settings due to the following factors. The relative photosensitivity of the layers of photo paper is determined by zonal sensitograms, which leads to color distortion caused by a vertical manifestation effect. The mutual influence of the layers during the development leads to the fact that the densities measured on the three-layer sensitogram and on the zonal sensitograms differ even if the color-separation properties of the densitometer-dye system are taken into account. The disadvantage of this method is the fact that when determining the color balance of the paper by the same density values, the colorimetric properties of different types of photo paper are not taken into account. For example, for one type of photo paper, color balance occurs when the densitometer readings for the blue, green, and red filters are equal. For a different type of photo paper, this may vary. When determining the balance by the photosensitivity of the negative, the balance by the contrast of the emulsion layers is not taken into account, which is also a disadvantage of this method.

 The aim of the invention is to improve the quality of color settings photographic printing device.

, γ $\genfrac{}{}{0ex}{}{\text{з}}{\text{j}}$ =

, γ $\genfrac{}{}{0ex}{}{\text{k}}{\text{j}}$ =

,
где D_j ^с, D_j ^з, D_j ^к - плотности тест-негативов в соответствующей зоне спектра.The goal is achieved by the fact that in the method of color adjustment of the photographic printing device, which consists in the formation of zone sensitograms, the relative photosensitivity of the emulsion layers of the photo paper is determined and the optical densities of the negative are measured, in order to improve the quality of the color setting, neutral-gray color prints are preliminarily produced by exposing the color photo paper , then, according to the obtained prints, measuring zone pallets are made, after which zone sensitograms with omoschyu neutral gray wedge and at least three test-manufactured color negatives, the relative values of each of the photosensitive layer and the negative photographic paper is determined by the formulas
lgS _j ^l = lgt-D _j ^l , lgS _j ⁿ = lgt-D _j ⁿ , lgS _j ^g = lgt-D _j ^g , where t is the exposure time of the zone sensitograms;
D _j ^jpg - the density of the field of the neutral gray wedge at which the density of the print is equal to the selected criterion of photosensitivity of photo paper
j is the number of test negative, and the relative slope of the partial characteristic curves of the negative is determined by the formulas
γ $\genfrac{}{}{0ex}{}{\text{c}}{\text{j}}$ =

, γ $\genfrac{}{}{0ex}{}{\text{s}}{\text{j}}$ =

, γ $\genfrac{}{}{0ex}{}{\text{k}}{\text{j}}$ =

,
where D _j ^s , D _j ^s , D _j ^k are the densities of test negatives in the corresponding region of the spectrum.

 The drawing shows a structural diagram of a photographic printing device.

 The device contains a light source 1, which is used as a lamp type KGM. In block 2, a turret with light filters (not shown) that transmit light in the blue, green, and red regions of the spectrum is installed. The filters can be sequentially installed in the luminous flux of the lamp, which is the additive method of photo printing. The exposure time behind each filter is set by the shutter 3. The optical system 4 form the light flux in the plane of photo printing of negative 5 and positive 6, which are in mechanical contact with the help of pressure glasses 7, 8. Above the pressure glass 8 is a scanning head 9 with a photodetector for measuring densities printed negativity. The signals from the photodetectors arrive at the microcomputer 10, where they are processed according to the corresponding algorithm. The processed signals control the operation of the filter turret and the shutter 3.

The device can operate both in automatic mode and in manual mode. Manual mode is intended for color adjustment in the factory during the manufacture of the device. Color adjustment by the method is as follows. By selecting an exposure time by the operator t _c , t _z , t _k for each filter, an imprint on the neutral-color color photo paper is obtained in the absence of negative. Control of "grayness" is carried out by densitometer or visually by the operator. Moreover, the total density of the fingerprint, determined by the formula
D _total = 0.1D _s + 0.6D _s + 0.3D _k , where D _s , D _s , D _k are the densities measured behind the corresponding light filter (blue, green, red), densitometer, should be within 0, 8 ± 0.1 B.

Then, a separate sheet of photo paper is exposed behind a blue filter with a time t _s , which was obtained in the manufacture of a neutral gray print. Two other sheets of photo paper are also displayed behind the green and red filters. After chemical-photographic processing, the sheets are cut to the required format and a hole with a diameter of 5-6 mm is cut out in the center of each sheet. Thus, three measuring sticks are obtained - yellow, purple, blue. Then proceed to the production of zone sensitograms. A discrete neutral gray wedge (not shown) made on a transparent base is mounted on the contact glass of the device. The wedge has 30 fields with a constant of 0.1 B. The density of the first field is at the level of the veil of the applied film. The optical density values are presented on the fields of the wedge so that their values are clearly visible on the positive prints. On the neutral gray wedge they lay the first test negative, made on a color film with a density of about 0.5 B. A sheet of photo paper is placed on top and exposure is performed for blue light filter. After the exposure is completed, the sheet of photo paper is changed and the exposure is carried out behind the green filter. In a similar way, the third sheet of photo paper is exposed behind the red filter. The exposure time in all cases is 10 s, provided that the illumination on the contact glass is in the range of 100-500 lux, and the photosensitivity of photo paper is in the range from 5 to 40 units of GOST 26661-85. After chemical-photographic processing of three sheets of photo paper, they begin to analyze the obtained zone sensitograms.

 Using the yellow palette, they search for the field on the first sensitogram whose density is visually close to the density of the palette. The value of the field density of the neutral-gray wedge, at which a coincidence of the colored fields of the sensitogram and the palette is obtained, is entered into the device memory. Similarly, the density of the fields of the neutral gray wedge is determined by analyzing the purple and blue palettes. The same thing is done when installing test negatives N 2 and N 3, the density of which is equal to 1.0 and 1.5 B. Thus, nine field densities of the neutral gray wedge are obtained.

The relative value of the photosensitivity of photo paper and negative, which are expressed in units of time, is determined by the formulas
lg S _j ^l = lgt-D _j ^l , lgS _j ⁿ = lgt-D _j ^p , lgS _j ^g = lgt-D _j ^g (2), where t is the exposure time of zone sensitograms, usually equal to 10 s;
D _j ^{W, p, g} - field density of a neutral gray wedge at which the field density of the sensitogram (yellow, purple, blue) is equal to the selected criterion of photosensitivity of photo paper;
j is the number of test negative.

, γ $\genfrac{}{}{0ex}{}{\text{з}}{\text{j}}$ =

, γ $\genfrac{}{}{0ex}{}{\text{k}}{\text{j}}$ =

,
где D_j ^с, D_j ^з, D_j ^к - плотности тест-негативов в соответствующей зоне спектра.The relative slope of the partial characteristic curves of the negative is determined by the formula
γ $\genfrac{}{}{0ex}{}{\text{c}}{\text{j}}$ =

, γ $\genfrac{}{}{0ex}{}{\text{s}}{\text{j}}$ =

, γ $\genfrac{}{}{0ex}{}{\text{k}}{\text{j}}$ =

,
where D _j ^s , D _j ^s , D _j ^k are the densities of test negatives in the corresponding region of the spectrum.

The obtained data on the relative values of photosensitivity and tilt are used to calculate the zonal exposure times using the formulas
lgt ^{s, s, k} = lgS _{j s} ^{, n, g} + γ _j ^{s, s, s} (D ^{s, s, k -} D _j ^{s, s, s} ), if D ^{s, s, s} <D _{j + 1} ^{s, s, c}
lgt ^{s, s, k} = lgS _{j + 1 s} ^{, s, g} + γ _{j + 1} ^{s, s, s} (D ^{s, s, k} - D _{j + 1} ^{s, s, k} ) if D ^{s, s, k} ≥ D _{j + 1} ^{s, s, k} , where D ^{s, s, k} is the density of the printed image in the corresponding region of the spectrum.

Claims (1)

METHOD OF COLOR SETTING OF THE PHOTO PRINTING DEVICE, which consists in forming zone sensitograms, determining the relative photosensitivity of the emulsion layers of photo paper and measuring the optical density of the negative, characterized in that, in order to improve the quality of the color setting, neutral-gray color prints are preliminarily produced by exposing the color photo paper , then, according to the obtained prints, measuring zonal palettes are made, after which zonal sensitograms are formed using th neutral gray wedge and at least three test-color negatives, the relative values of each of the photosensitive layer and the negative photographic paper is determined by the formulas
log S _j ^f = log t - D _j ^f , log S _j ^p = log t - D _j ^p , log S _j ^g = log t - D _j ^g ,
where t is the exposure time of zone sensitograms;
D _j ^{W, p, g} - field density of a neutral gray wedge, at which the density of the print is equal to the selected criterion of photosensitive photo paper;
j is the number of test negative,
and the relative slope of the partial characteristic negative curves is determined by the formulas
γ $\genfrac{}{}{0ex}{}{\text{c}}{\text{j}}$ =

,
γ $\genfrac{}{}{0ex}{}{\text{s}}{\text{j}}$ =

,
γ $\genfrac{}{}{0ex}{}{\text{k}}{\text{j}}$ =

,
where D _j ^c , D _j ^s , D _j ^k are the densities of test negatives in the corresponding spectral region.

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