قدرة الطبقة الحساسه على تسجيل التفاصيل بدقه .. كتاب الإضاءة والفلم

Chapter VIII

The ability of the sensitive layer to accurately record details

It is noticed that there is confusion between three names that were designed to describe the ability of the sensitive layer in the film to accurately record the details, and these names are:

1- Sharpness

2 -- Lit (1) Acutance

3- Resolving power

The sharpness of the image is a subjective expression decided by the beholder of the image to judge the extent of its accuracy in conveying the details of nature, and at that time he relies on his visual sense, so he says, for example, when seeing it, that this image is Objective (2) and the image is illuminated (3) Acutance: It is an objective expression developed as a scientific means to measure the degree of sharpness of the image perceived by the individual. The intensity. It is an expression decided by the seer based on his visual abilities, which depend to a large extent on physiological factors. As for Acutance, it depends in his decision on scientific devices and physical means.

Perhaps the following example explains the subject more accurately: Supposing that we have placed a white thread on a black ground, then we examine the negative image microscopically in order to see the boundaries separating the black area (which represents the white thread in nature) and the white transparent area (which represents the black ground). Originally) Here we see that if there is a contrast between each of the two regions without a gradation between them in colors, we will express the image as sharp, as the sharpness has arisen from our visual awareness of the great difference in Photographic density between the white and black regions, and vice versa, if we see gradations gradation between the white and black areas, this indicates that the image is not sharp. And the transfer of image sharpness as the distance of these gray gradations increases.

If we wanted to measure the photographic intensity of each of the white and black regions, we would determine the degree of this sharpness by using scientific equipment and means to estimate a numerical value for this sharpness. In fact, we require an estimate of the degree of light Acutance, and this process begins with measuring the photographic intensity in each of the transparent white parts and the neighboring black parts. Higgins and Jones laid the scientific basis for the measurement of (luminous).