مشاهدة الصور الموجبة الشفافة .. كتاب التحميض والطبع والتكبير

See the transparent positive images:

Transparent positive images can be seen with transmitted lighting, according to one of the following methods:

1- By directing it towards the source of light, which is a method that allows only one person to see it.

2- By means of small light boxes called Slide Viewers, which also allow only one person (Fig. 99) or a limited number of people (may not exceed three) to view the image (Fig. 100).

3- By projectors, which is the best and most common way, as it allows a large number of viewers to see the image.

Factors affecting the intensity of photo luminance:

The image that is prepared for display is required to be completely sharp and equal in intensity of illumination, whether in all corners or in the middle, and it should be as bright as is comfortable for the eye.

The intensity of the illumination of the image depends on several factors, which can be summarized as follows:
(a) Image density, or in other words, its transparency.

(b) The amount of light energy emitted by the lamp.

(h) The diameter of the two condenser lenses, and the width of the projector lens aperture.

(d) The distance between the lens of the projector and the screen on which the light image falls. If the degree of enlargement of the image increases as this distance increases, the intensity of its illumination decreases accordingly, and is inversely proportional to the square of the distance.

(e) The color of the frame surrounding the display screen, so the image appears brighter if the screen frame is black.

(f) The type of display screen, there are glossy, beaded screens and white matte screens, and each has distinctive characteristics (and we will talk about that later).

Factors affecting image sharpness:

The Sharpness of the image displayed on the screen depends on the following factors.

1- The degree of sharpness of the original positive transparent image, and therefore extreme accuracy should be taken into account in adjusting the focusing distance during imaging, especially if the original image is of a small size (on 35 mm film, for example).

2 - High contrast images appear sharper when displayed on the screen, and vice versa.

3- The degree of quality of manufacturing the optical system in the projector, and what is meant by the optical assembly is each of the combined mirror, the optical condenser, and the lens of the projector, and here we mention that when manufacturing these devices, the distances between each of the previous elements are accurately estimated arithmetic, and therefore it is necessary to maintain the distance of the other Without trying to disassemble it or change anything in it, unless this is known by the best trained person who has studied its parts completely.