JPS6242496B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a photographic printing exposure amount control method for controlling the exposure amount so as to obtain photographic prints with appropriate printing density in negative-positive type photographic printing. Conventionally, this type of exposure control method involves quantizing the difference between the average density at the center of the screen and the average density at the entire screen, and the difference between the average density at the upper part of the screen and the average density at the lower part of the screen, and using this combination logic. It has been proposed to classify negative film into multiple categories, calculate the exposure amount based on a preset exposure correction term for each category, and correct the basic exposure control formula based on this. (Tokukai Akira
52-23936). That is, the exposure amount is controlled by adding a correction term q=k ₃ CF+k ₄ UL+k ₅ RL in which a coefficient Ki is set according to the type of negative film to the exposure amount control basic equation x= _{k 1} +k 2 CP. Here, CP = (Dmin + CN / 2) - LATD (W) CF = DC - DF UL = DL - DU RL = DRI - DLF k ₁ - k ₅ : Constant LATD (W): White whole screen average density Dmin: Minimum white density Dmax: Maximum white density DC: Average density at the center of the screen DF: Average density at the periphery of the screen DU: Average density at the top of the screen DL: Average density at the bottom of the screen DRI: Average density at the right side of the screen DLF: Left of the screen This is the square average concentration (see Figure 1). The exposure amount control method described above has the effect of improving yields because even negative films containing density defects (subjective density defects) can be finished as photographic prints with appropriate density. As mentioned above, this method quantizes the difference between the average density of the center of the screen and the average density of the whole screen, and the difference between the average density of the upper part of the screen and the average density of the lower part of the screen, and combines the negative films (scenes) into multiple This is to classify the images into categories and select a preset coefficient for the exposure correction term according to the fraction. The quantized characteristic values in this case are simply combined mechanically, and therefore, once the combination of quantized characteristic values is determined, the classification of the negative is inevitably determined. The exposure compensation term consists only of combinations of densities at the top/bottom, left/right, and center/periphery of the screen, so it is useful for negative film taken in backlit situations with a lot of sky, landscapes, winter gardens, etc. may not be able to achieve the proper density. For example, the correction term q is
Since there is k ₄ UL, correction is made for backlight, but if more than 3/4 of the sky is included,
Since the value of UL becomes small, effective correction cannot be performed. Furthermore, since the basic exposure control formula does not include a characteristic value that represents the average contrast of the entire screen, the density of landscapes will be too high, and the density will be too high for objects such as landscapes, and for objects exposed to sunlight such as in a winter garden. If there are both shaded areas and shaded areas, the density will be too low, making it impossible to obtain good photographic prints. The present invention solves the above-mentioned drawbacks, and provides a photographic printing exposure control method that allows negative film to be finished at an appropriate density even when photographing under backlight with a large amount of sky, landscapes, winter gardens, etc. The purpose is to provide The printing exposure control method of the present invention does not classify negatives by simply combining characteristic values obtained by measuring negatives and quantizing or digitalizing them, as in conventional methods. From the values obtained, special image groups such as negatives with low contrast images, negatives with high contrast images, underexposed negatives, and overexposed negatives are extracted, and the optimal exposure control formula is applied to these image groups. , which provides an exposure control formula suitable for the remaining image negatives as well. Here, "a numerical value obtained by measuring a negative" means a value measured at a large number of measurement points determined over the entire negative. The present invention controls the exposure amount during printing using an exposure amount control formula that includes contrast information and color information in addition to maximum density information, minimum density information, and average density information for the entire negative screen and portions. Then, the above-mentioned special image groups are extracted and classified based on various density information of the measured negative, and a separate exposure amount control formula is calculated according to the classification results. That _is , _the exposure control method of the present invention uses _an exposure control formula in _{which a} coefficient _Ki is determined for _each classified _pattern . )
...It is characterized by being printed based on (1). In the above formula (1), DB is

[Formula] This is the average value of the difference between adjacent measurement points and represents the average contrast of the entire screen.
Moreover, IR (W) is the number of white pieces. In reality, if the blue density is B, the green density is G, and the red density is R, what is included in a circle with a radius of 0.1 centered on the coordinate origin in two-dimensional coordinates with G-B and RG as axes? Defined as white. Therefore, something like a white cloud falls under this category. Since the above formula (1) includes K ₇ DB and K ₈ IR (W), it is difficult to capture images taken under backlight with a lot of sky, landscapes, etc.
Even things like a garden in winter can be printed at the appropriate density. For example, when there is a lot of sky, the value of the characteristic value K ₈ IR(W) (K ₈ <0) increases, so negative correction is made and the human face does not appear dark. Furthermore, in the case of landscape, the characteristic value K ₇ DB
Since the value of (K ₇ > 0) becomes small, it is corrected negatively, and since things like a garden in winter become large, it is corrected positively. The result is a photographic print with appropriate density. The present invention will be explained in detail below. FIG. 2 is a flowchart outlining the present invention. First, the full screen density characteristic value of negative film
LATD (W) Dmax, Dmin, DB, IR (W) partial screen density characteristic values DL, DU, DRI, DLF, DC,
Measure DF, FMAX, CMAX. CMAX here
is the maximum density at the center of the screen, and FMAX is the maximum density at the periphery of the screen. Using these characteristic values, each negative film is classified into the following patterns. a Under-contrast b Over-contrast c Not under- or over-contrast, with CN≦1.0 d High-contrast, neither under-nor-over, CN≦1.2 e For a) to d) above What is not included The above a) to e) are, for example, in the following range. a Under Dmax≦1.1 or LATD(W)≦0.4 b Over Dmin≧0.6 or LATD(W)≧1.0 c Neither under nor over, low contrast CN≦1.0 and CP−0.2LATD(W)< +0.05 d High contrast, neither under nor over CN≧1.2 e Items not included in a) to d) above (average pattern with proper exposure) The characteristic value CN used for the above classification is white Maximum density Dmax (W) and minimum density Dmin (W) of white
This is the difference. _{After these classifications , the exposure control formula}
In (1), Ki is defined for each category based on experience, and the exposure amount is controlled using a formula. That is, a Under X ₂ = b ₁ + b ₂ Dmax + b ₃ Dmin - b ₄ LATD (W) +
b ₅ CF+b ₆ UL+b ₇ DB...(3) b Over X ₃ =-c ₁ +c ₂ Dmax+c ₃ Dmin-c ₄ LATD(W)
+c ₅ CF+c ₆ UL+c ₇ DB−c ₈ IR(W) ……(4) c Low contrast, neither under nor over X ₁ =a ₁ +a ₂ Dmax+a ₃ Dmin−a ₄ LATD(W)+
a ₅ DB−a ₆ IR(W) ……(2) d High contrast, neither under nor over X ₄ =−d ₁ +d ₂ Dmax+d ₃ Dmin−d ₄ LATD(W)
+d ₅ CF+d ₆ UL+d ₇ DB−d ₈ IR(W)
...(5) e Other than the above a to d X ₅ =-e ₁ +e ₂ Dmax+e ₃ Dmin-e ₄ LATD (W)
+e ₅ CF + e ₆ UL + e ₇ DB ... (6) Each characteristic value is substituted and calculated according to the exposure amount control formulas (2) to (6) determined for each classification. The exposure time may be controlled based on this calculated value. For classification c, a ₇ IR (G) + a ₈ IR is added to formula (2).
The term (R) may be added. IR(G) is the number of green colors, and IR(R) is the number of red colors. IR
(G) is effective for negative films containing grass, and IR (R) is effective for negative films containing autumn leaves, and positive correction is performed by these terms, resulting in a higher density. Furthermore, from the negative group in e), FCMAX≧0.2, CP≧0.1 as a negative group that includes the sky in a part of the screen.
and divided by CF≦0.1, X ₇ = f ₁ + f ₂ Dmin−
f ₃ LATD (W) + f ₄ CF + f ₅ UL + f ₆ DB ... (7) may be added. This prevents the image from becoming too dark when there is sky around the periphery of the conventional screen. Here, FCMAX is FMAX-CMAX. Note that the coefficients Ki, that is, ai to ei in each case of a to e, can be set as follows, for example. When under, b ₁ = 0.07 b ₂ = 0.32 b ₃ = 1.25 b ₄ = 1.65 b ₅ = 0.27
b ₆ 0.27 b ₇ = 1.23 When over c ₁ = 0.58 c ₂ = 0.59 c ₃ = 0.19 c ₄ = 0.79 c ₅ = 0.98
c ₆ = 0.24 c ₇ = 1.38 c ₈ = 0.001 When the contrast is low, neither under nor over, a ₁ = -0.23 a ₂ = 0.70 a ₃ = 0.70 a ₄ = 1.67 a ₅ =
2.18 a ₆ = 0.004 When the contrast is high without being under or over d ₁ = −0.14 d ₂ = 0.36 d ₃ 0.36 d ₄ = −0.90 d ₅ =
0.87 d ₆ = 0.25 d ₇ = 1.91 d ₈ = −0.002 Other e ₁ = 0.11 e ₂ = 0.59 e 3 = 0.59 e ₄ = _1.48 e ₅ = 0.59
e ₆ = 0.31 e ₇ = 1.31 e ₈ = 0.001 After or before the classification, those with a left-right density difference or a top-bottom density difference equal to or greater than a certain value are extracted. Based on this difference in density between the left and right sides, it is possible to determine whether the sky is visible on the left or right side of the photograph, since the photograph was taken with the camera in a vertical position. In this case, since the vertical and horizontal directions are reversed, it is necessary to replace UL with RLA in each of exposure control formulas 2 to 7. Here, RLA is the absolute value of RL, that is, |DRI−DLF|. Also, most of the images with a large difference in density between the top and bottom are those taken under backlight, those with snow at the bottom of the screen, and those with concrete at the bottom of the screen. Moreover, although most cameras shoot from left to right, only about 5% of the images are taken by cameras that shoot from right to left, and the signs of these ULs are reversed. Negative correction (reducing density) is effective in the case of backlight and snow, and positive correction is effective in the case of concrete. Therefore
Replace UL with ±ULA or zero depending on the scene. Here, ULA is |UL|. For the same reason, UL→±RLA or zero is also substituted for the case where there is a difference in left and right density. g Items with a left-right density difference RLA≧1.5 h Items with a top-bottom density difference ULA≧1.5 Items with a left-right density difference are replaced using the following discriminant. XX=0.3+0.8LATD(W)+1.5CF−0.5UL−
1.1DLF−0.0008IR(W) ……(8) If XX≧0.09, UL→RLA If XX≦−0.9, UL→−RLA If 0.09<XX<−0.09, UL→zero. For those with a difference in upper and lower density, use the same discriminant formula.
Replace UL → ±ULA or zero. According to the present invention having the above configuration, since the terms DB and IR (W) are added to the exposure control equation, the appropriate density can be achieved even when shooting negative films such as backlit scenes with a lot of sky, landscapes, and winter gardens. can be printed on. In addition, visual judgment was performed on 2,175 printed photographs to determine if an area within ±20% of the target density was acceptable.
%, whereas in the present invention, it was 89.0%, which was quite good.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a negative film showing a divided screen, and FIG. 2 is a flowchart of the present invention.

Claims (1)

[Scope of Claims] 1. Based on characteristic values obtained by scanning a film screen, such as a full screen density characteristic value, a partial screen density characteristic value, or a combination thereof, a negative film image is determined to be at least a. b Items that are over c Items with low contrast that are neither under nor over and in the range of CN≦1.0 d Items with high contrast that is neither under nor over but in the range of CN≧1.2e Items that are not included in a) to d) above Calculate the exposure control formula X=K ₁ +K ₂ Dmax+K ₃ Dmin+K ₄ LATD(W) +K ₅ CF+K ₆ UL+K ₇ DB+K ₈ IR(W) by classifying into 5 types and setting the coefficient Ki in advance according to this classification. A photographic printing exposure amount control method characterized in that the printing exposure amount is controlled based on the calculation result. (Here K ₁ to _{K 8} are coefficients, Dmax is the maximum density of white, Dmin is the minimum density of white, LATD
(W) is the average density of white throughout the screen, CN is the difference between the highest and lowest density of white, CF is the average density at the periphery of the screen, UL is DL-DU, DL is the average density at the bottom of the screen,
DU is the average density in the upper part of the screen, DB is The average value of the difference between adjacent measurement points represents the average contrast of the entire screen. IR(W) is the number of white pieces. )