قوة التحديد في الطبقة الحساسة .. كتاب الإضاءة والفلم

Selection strength in the sensitive layer
Resolution Resolving Power

The power of definition in the sensitive layer is defined as the ability to record adjacent points or lines in the original being photographed so that these points or lines appear completely defined in the image and each of them is completely separated from its neighbors. The power of determination in the image does not depend merely on the characteristics of the sensitive layer, but it also depends on the optical means that were used to transfer it, i.e. it depends on the characteristics of the lens used and the extent to which it overcomes optical defects.

And since we have already talked in detail about the power of determination in the lenses in the camera book, therefore we will suffice here to discuss the power of determination in the sensitive layer.

The strength of determination is measured by the number of lines (in millimeter) that are recorded on the sensitive layer when photographing a test plate with similar lines, each separated from the other by a distance equal to the thickness of the line itself. (s.t). If we suppose that the measurement during the microscopic examination showed us that the thickness of each line in the negative image is -b of a millimeter, then the determination strength is estimated.

There is no doubt that such a result must be indicative of the strength of determination in both the lens and the sensitive layer. Experiments have proven that the limiting force resulting from the lens only always exceeds the limiting force resulting from both the lens and the sensitive layer, and it is concluded that the limiting force of the sensitive layer is always transferred from the limiting force resulting from the lens. For example, if the power of determination that you get from the lens. certain equals
(100 lines / millimeter) by which it was possible to obtain, when using a sensitive layer with a speed of 32 Shiner, a limiting force of
(30 lines / millimeter) and if we used another lens with a limitation strength of (300 lines per millimeter) on the same sensitive film, it would be possible to obtain a limitation strength in the negative image of the amount
(approximately 50 mm line). There is no doubt that we have noticed in the previous two examples that the ratio between the power of determining the sensitive layer and the power of determining the lens was not uniformly consistent. .

And it was necessary for us to conduct the power of determination in this manner in the second example, that is, if it is:

The lens sq = 300 millimeter lines should have been s. Image T = 90 millimeter lines. But as we saw in the second example, Q was not equal to 90 millimeter lines, rather it was only equal to 50 millimeter lines, and perhaps the correct reference that guides Q. t is an experiment and graphs showing the relationship between s . v lens s . The film on which the test is conducted.

The effect of light wavelength on the strength of determination in the sensitive layer:

And just as the length of the light wave that passes through the lens has an effect on the power of resolution in the lens (1), the length of the light wave also has an effect on the s. T in the sensitive layer, where it increases. Also, the shorter the light wavelength, the short-wave blue rays lead to a determination power that exceeds the determination power that you get if the rays that affected the sensitive layer were long-wave such as the red rays, for example. And the results that we mention in the following support what we say (2).

It is not difficult to explain these observations and to imagine the extent to which these results correspond to reality if we know that the long-wave rays have the ability to penetrate the sensitive layer more than the ability of the rays with shorter waves (1), and the greater the penetration of the rays in the sensitive layer, the greater their non-dissemination Direct and unwanted, so the power of determination decreases, and we have already talked about the effect of this indirect diffusion on the sensitive layer (Fig. 41 p. 115).

The previous facts also explain the reasons for which it may be noted that the power of identification in a specific area of ​​the negative image may exceed another area of ​​the same negative. This may be due to the different color of the objects being photographed. Blue objects reflect short-wave rays from them, which leads to a large identification force. And red objects reflect long-wave rays, thus decreasing the power of determination. It also follows that the determination power decreases when using long-wave infrared rays and increases when imaging with short-wave ultraviolet rays.

The effect of exposure to light on the strength of determination in the sensitive layer

To get the best degree of sharpness, exposure must be properly judged. As both the increase or decrease in exposure to light results in results that harm the strength of determination in the sensitive layer, as a result of the decrease in exposure to light from the appropriate limit, the degree of contrast decreases on the one hand, and on the other hand, the exposure processes only lead to reducing the highly sensitive silver bromide granules only, and both factors The former two reduce the power of selection.

Likewise, to increase the exposure to light beyond the appropriate limit has a bad effect on the strength of determination, as the number of grains of silver salt that accept reduction increases in the display solution, and the penetration of rays into the lower layers of the sensitive film increases, and these two factors also reduce the strength of determination and explain (Fig. 51) The effect of increasing the exposure to light on the determination power.