القواعد العامة لتصحيح الألوان بطريق الإضافة .. كتاب التصوير الملون

General rules for color correction by addition:

The general rules followed in correcting colors by addition differ from those followed in correcting them by deletion, and let us give the following examples: - Assuming that it appears that the positive image suffers from a compound red tinge covering it, the reference to this may be that the two layers that bear the problems of the color vermilion (i.e. sensitive to green rays), and yellow color problems (i.e., the sensitive layer to blue rays) in positive photosensitive paper have been overexposed, because increasing the yellow and crimson colors causes an increase in redness of the image.

In this case, the following color images shall be processed in any of the following two ways: (a) Either by increasing the exposure with the red light source (or through the red filter).

(b) or underexposed with the green and blue light sources (or through the green and blue filters). (2) Assuming that the initial image prepared for the test print suffers from a compound blue tinge, this may be due to overexposing each of the two carrier layers to the problems of cyan and magenta (because blue is scarlet). The treatment in the following images is either by increasing the exposure with the blue light source: or by decreasing the exposure with the red and green light sources = cyan +

) Assuming that the image suffers from a slight yellow tinge, this may be due to the fact that the blue-sensitive layer that bears the yellow color problems has been overexposed, and thus the colors in the following images are corrected by increasing the exposure with the red and green light sources. (because yellow = red + green) or by underexposing the blue light source.
To increase the quantity, and we summarize the following general rules for color correction by addition: - First: In order to correct a smear of a specific color, it is necessary for light of a color similar to the color of the smear. Secondly: It is necessary that the amount of increase in exposure with a source of a certain color be directly proportional to the intensity of the smear in the positive image. Third: Assuming that the correction is more than the appropriate amount, then it is certain that a new shade will arise from a color that is complementary to the color of the original smear. photo too. And in Figure 63 p. 215 in the colored plates, an explanation and summary of these rules.

Imprints or color enlargement according to the addition method

The following are to blame for colored magnification according to the method of addition: (1) The three exposures may require long periods of time that cause boredom, especially if it is necessary to increase the zoom ratio, and the image is dense 2) It is possible that the final image will not be completely sharp as a result of any vibration of the magnifier or stand Negatives or sensitive paper when changing filters, and for this reason, the magnifier must be completely stable and not subject to vibration at all.

It is possible during the colored enlargement by deletion to cover (shade) some parts of the image, dodging or shading, while this may not be performed successfully if the exposure is made in three batches according to the method of addition.
Print color negatives to obtain photo positives on black and white paper

Colored negatives can be printed on bromide sensitive (black and white) paper. But since the spectral sensitivity of these papers reaches its maximum with respect to blue rays, and is much lower with respect to green rays, and is almost not affected by yellow and red rays, therefore it is certain that the tonal values ​​are not faithfully transmitted, and let us take an example of this in the case of photographing a blonde girl with blue eyes and lips Two reds:

The color of the original subject in nature

Color these parts in the color negative

Bromide sensitivity color photo negative paper

Color these parts in the black and white positive image on the bromide paper

The hair is yellowish blond. Blue eyes, red lips

dark blue

usher

yellow

Partially insensitive

Green Blue (Cyan) |

Thus, we see from the previous explanation that the values ​​of the natural colors were not conveyed faithfully when the colored image of that subject was printed or enlarged on bromide paper.

Black and White" .

Therefore, Kodak factories produced sensitive paper for this purpose, characterized by being panchromatic materials that are sensitive to all colors, and this paper is known as Panalure Paper.