JPH0746205B2 - Exposure determination method for photo printing - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for determining an exposure amount for photographic printing.

-Background of the Invention-Generally, a negative image that has been taken is not necessarily taken under a condition suitable for printing, and various kinds such as overexposure and underexposure, various photographing light sources, defocus, difference in color sensitivity of film, etc. There are changes due to factors. For this reason, the exposure amount and color balance of each frame of the negative image are appropriately adjusted during photo printing. Among them, for the exposure amount adjustment, there is a method of determining from the average transmission density (LATD) for each frame of the negative image. In this method, it is often impossible to correct a negative image when the luminance configuration is extremely biased compared to the normal luminance distribution.

Therefore, a method is proposed in which the transmission density of a region obtained by dividing a negative image into multiple areas is measured, and the basic exposure amount according to the scene is statistically obtained by classifying into a representative pattern of the subject scene based on the size of the density difference and the density distribution. Has been done.

-Problems to be solved and used by the invention-Since the conventional exposure amount determination is determined by a statistical method, the exposure amount may be inappropriately set depending on the negative image. However, there was a problem that a few percent of the reheating would occur. An object of the present invention is to provide a method for determining an exposure amount that reduces the occurrence of reprinting.

-Means for Solving the Problems-In order to achieve the above-mentioned object, the present invention provides a method for determining a photographic printing exposure amount for printing a negative image recorded on a negative film on photographic paper, wherein the negative image is transmitted. The density is read, the average transmission density and the transmission density distribution of the negative image are obtained from the transmission density, and it is calculated based on the exposure amount (1) calculated from the average transmission density and a plurality of parameters in the transmission density distribution. The exposure amount (2) is calculated from the exposure correction amount, an evaluation value for the exposure correction amount is obtained based on a plurality of parameters in the transmission density distribution, and the exposure amount (2) is calculated based on the evaluation value. It is determined whether or not printing is performed, printing is not performed with the exposure amount (2), or the exposure correction amount is corrected.

-Embodiment- FIG. 1 is a device configuration diagram showing an embodiment of the present invention. The negative film unit 1 feeds the roll film wound with the negative film 2 to the position of the optical printer 3 by frame feeding. The optical printer 3 is configured to print a negative image for each frame on the photographic paper 4 while the negative film 2 is being moved. Photographic paper 4
Is taken out from the paper rewinding section 5 as roll paper.

The printing condition of the optical printer 3 is given as a set value from the processing device 6 such as a computer, and the printing condition is determined according to the read signal from the negative reading unit 7. The negative reading unit 7 is located in front of the negative printing position of the optical printer 3 and reads the transmission density of the negative film 2 frame by frame and pixel by pixel.

The exposure amount determination method among the printing conditions by the processing apparatus 6 will be described in detail below in comparison with the conventional method.

The conventional exposure amount (that is, exposure time) T is expressed by the following general formula.

T = f (D) + f (CV) + ... f (Z) (1) In this equation (1), f (D) is obtained as a function of the average transmission density D, and f (CV) is a statistical method. Exposure correction amount CV
Is obtained as the sum of the function f (Z) of other correction elements (here, Z) in addition to these functions. Here, the exposure correction amount CV is determined by the following equation (2).

Here, X _i is a representative parameter in the concentration distribution, C _i is an experimentally obtained coefficient, n is the total number of representative parameters, and b
Is a constant that is experimentally obtained.

Although such a conventional exposure amount determination method is uniquely obtained based on the transmission density detection signal of the negative image,
There is a certain probability that a non-conforming printing condition, that is, a non-conforming exposure amount may result depending on the shooting state of the negative image.

Therefore, in the method of the present invention, an evaluation amount for the exposure correction amount CV is introduced to reduce the number of non-conforming exposures as much as possible, and consequently to reduce the occurrence of reprinting.

For example, the absolute value (evaluation value) ΔCV of the difference between a certain exposure correction amount CV and the ideal optimum correction amount is It is determined that However, X _i is a representative parameter in the concentration distribution, d _{i is an} experimentally obtained coefficient, and e is an experimentally obtained constant.

The evaluation value ΔCV thus obtained is related to the probability that the exposure correction amount CV is different from the optimum correction amount, and the relationship between the probability of good printing and the prediction residual ΔCV is shown in FIG. Now, assuming that the correction value CV ₁ and the evaluation value β have been calculated for a certain negative image, it can be predicted that a negative printed with the correction value CV ₁ can be satisfactorily printed with the evaluation value β with a probability of γ.

The probability function g (ΔCV) indicating such a probability value can be defined as a linear or quadratic expression in the range of 0 <g (ΔCV) <1.

With the introduction of the above probability function, the allowable print level is set in advance as the reference value of the probability value, and if the probability value does not reach the reference value, printing is not performed or the operator is prompted to judge. The quality above a certain level can be guaranteed in the printing process.

By manipulating such a probability value, the quality of the printing process can be controlled to a level higher than that of a certain lens, which in turn can reduce the occurrence rate of reheating.

-Effects of the Invention-As is apparent from the above invention, since the present invention introduces the evaluation value for the exposure correction amount, the print quality is guaranteed and the print quality is improved as compared with the conventional unique exposure amount determination method. This has the effect of reducing the occurrence of repair.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an apparatus for explaining the present invention, and FIG. 2 is a characteristic diagram of an evaluation value ΔCV and a probability γ of good printing in the method of the present invention. 2 ... Negative film, 3 ... Optical printer, 4 ... Printing paper, 6 ... Processing device, 7 ... Negative reading unit.

Claims (1)

[Claims] 1. A method for determining a photographic printing exposure amount for printing a negative image recorded on a negative film on photographic paper, wherein the transmission density of the negative image is read, and the average transmission density and the transmission density of the negative image are read from the transmission density. A distribution is obtained, and an exposure amount (2) is calculated from an exposure amount (1) calculated from the average transmission density and an exposure correction amount calculated based on a plurality of parameters in the transmission density distribution, An evaluation value for the correction amount is obtained based on a plurality of parameters in the transmission density distribution, and whether the exposure amount (2) is used for printing or the exposure amount (2) is not used, based on the evaluation value. Or a method of determining a photoprinting exposure amount, which comprises determining whether to correct the exposure correction amount.