الخطوات العملية التي تتبع لاصلاح الألوان بطريق الحذف .. كتاب التصوير الملون

The practical steps that follow to fix the colors by deletion

Basic Correction numbers

There is no doubt that it is possible to start the process of enlarging or printing the color image by printing a single copy without using any optical filter (this is usually known as a zero print because the value of the filters = zero), then we use this print to study its color tinges, and then We then estimate the values ​​of the filters needed for correction. Likewise, it is possible, in order for the colors of the image to reach the closest degree of correctness, to replace the (zero print) by making a preliminary print, which initially obtains color correction by a certain amount that depends on calculating what is known as the basic correction numbers, and this is an expression given to the set of numbers that we show. Below : -

(a) Basic Positive Correction Numbers for the positive paper or film

They are a set of numbers that are printed on an envelope or tray of sensitive paper, and they differ from one envelope to another according to the type, recipe, and sensitive emulsions used in the manufacture of film or paper, as it is known - as we have already mentioned - that it is not possible at the manufacturing stage to prove Characteristics of all papers or films produced by a single plant. Although it may not. The photographer - in practice - only needs to know these numbers, but I remind you in this regard that the factory estimates these numbers based on tests that it performs on each type of sensitive emulsions to find out the value of optical filters that ensure the formation of a neutral gray image (i.e. black and white) on paper A color sensor if it is printed or enlarged negatively, black and white,
When using a light source that emits white rays (ie a source with good properties), its specifications are specified in the factory.

b Basic correction numbers appropriate for negativity:

Basic Negative Correction Numbers

They are numbers that specify the set of filters that, if added to the numbers of the basic correction of positive raw materials, it would be possible to obtain a neutral gray image from a colored negative film on which a gray card image was recorded divided into parts that range from white to black (grey scale) and between them are different gray degrees of value, assuming The imaging will take place in the light of a source that emits white rays whose specifications are predetermined by the factory that produces these negative films. Accordingly, we conclude that the combination of these numbers indicates the filters that ensure the correction of what may have affected the colored negative materials, such as an imbalance in the correctness of their colors.

(c) Specific Correction Numbers The colors of the image are affected by the characteristics of some parts of the devices used in the printing or enlarging operations. The light source, condenser, lens, etc. are all optical parts that have spectral characteristics related to them. These characteristics differ according to the type of optical glass and the extent of chromatic aberration correction, polishing, or other treatment during the manufacturing stages. Hence, we see that scrutinizing accuracy in work calls for searching for correction numbers associated with each printing or enlarging device. These numbers are what we call the qualitative correction numbers. It is evident that the numbers are subject to adjustment, and if any change occurs in the parts of the device (such as changing the lens), this correction will not be corrected

Or change the light source or change the capacitor, for example).
It is possible to determine the qualitative correction numbers according to the following: - It is placed in the holder of the negatives in the printing or enlarging device. Neutral negative image: black and white, then printed on sensitive paper or colored film, and the experiments are corrected until it is finally possible to obtain a neutral gray image, black and white, on this sensitive colored paper. Let us suppose that the filters that were required to obtain this color-neutral image are (25) - (50). If we subtract from these numbers the value of the correction numbers for the positive color-sensitive paper (which are shown on the paper envelope), and suppose that it was (10-15) We were able to determine the specific correction numbers of the printing device. According to this example, these numbers are as follows: - The group of correction numbers that ensured that we get a positive image (black and white, on colored paper). Correction numbers for the colored positive sensitive paper = 10-15 ... The specific correction numbers for the enlargement device B = 25 50 = 15 35 =