تكبير السلبية الملونة على ورق حساس ملون ٢_a ..كتاب فن التحميض والطبع والتكبير

yellow, yellow + cyan, magenta + cyan). That is, the delete filter, like yellow: contains an amount of red half of what is contained in a red filter with the same

consistency

For example, the effect (such as filter 0, a red filter of intensity 10 degrees, R10, gives the same red) as that given by two filters, one yellow, Y10, and the other, magenta, M10. If we have a package of filters, for example: 10 + R10 + Y20, we find that it is equal to a package consisting of: 20 + Y30, and it is also equal to a package consisting of R20 + Y10, because Y10 + M10 = R10

Number of So we find that we can find a particular color using different combinations of filters. And the best group is always the one that contains the least filters, and the least dense, and thus requires the least exposure time in the amplifier, such as the third group in the previous example, and let us consider together a group of filters such as (20 40 C10) we find that the presence of three omitted filters together cancels the work of each other What you do is increase the density. And to give the same short spectral change the same value from each filter, and thus the group becomes (Y30 M10) and this group gives a better exposure time.

31 Additional filtering of a sample of sensitive paper: It is noted that it is not possible to completely control the properties of sensitive paper during its manufacture, and thus we find that some samples differ in color from other samples. Therefore, we will find on the sensitive paper box or bag numbers such as (10 10). This means that this filter must be added to the main filter of the amplifier
= So the new time to get a well-exposed image: 10 x 1.5 = 15 seconds

Now to a practical example of adjusting the colors:

In the stage of adjusting the exposure, we obtained the appropriate time, for example 10 seconds) with an aperture of (8) on a paper whose area is (108) (inches). Magenta color example from

what do we do

A - We do an experiment on a slide of sensitive paper like the one on which we conducted the exposure experiments, but with the difference in filtration in this case instead of the difference in time. a

And since the smear was (magenta), then it is necessary to add a filter in the same color as magenta, or delete a filter in the complementary color (green i.e. yellow + cyan).

For ease we choose to add a magenta filter

So we show one-fifth of the paper with the filter of 150M908 at the same time (10 seconds). And we show the second five (only) with the nomination of 90 60M

And we show the third fifth (only) 90 70M, and so on, with an increase of 10 degrees magenta each time.

B - Acidify the experiment slide and decide which five colors are good? For example, the five that was presented with the nomination of 70M 90Y. That is an increase of 20

Filter coefficient 20M = 1.5 from the filter coefficient table in the appendix).

The new time = the old time x the filter coefficient. = 10 sec x 1.5 = 15 sec.

In the case of decreasing the density of filters, it will be old time new time: = filter parameter

A- We display the sensitive paper in the full size of 81 x 10 inches (with the new filter) (for example 90 by 70, which equals (20 by 70 R) for the new time, for example 15 seconds) and acidify it, thus obtaining a well-exposed image with good colors.

D - Do not forget to record what you did so that you can reproduce exact images from this negative or from this film if it was all shot under light conditions.

similar

E- From the previous operations, we obtained a well-exposed and well-colored image of a specific size of sensitive paper (for example, 8 x 10 inches). Suppose we want to obtain an image of another size of 129 cm. We note that the area of ​​the new size is about the area of ​​the old size known at the time of its exposure. D.

... The new size of paper needs approximately the previous exposure time or close the aperture two degrees. That is, the new exposure time becomes " = 32 seconds

Or the aperture becomes F16.

And - it is noted that the nomination does not change with the change of magnification.