تكبير الصور .. كتاب التحميض والطبع والتكبير

Chapter Nine
Enlarge photos

ENLARGING, PROJECTION-PRINTING, BLOWING
This process was done by means of a magnifier, which may be vertical (Fig. 55-1) or horizontally (Fig. 55b), and it has a light source that emits rays that pass through the negative image, then through a collecting lens that enlarges the image and projects it on sensitive paper. And we show in (Fig. 56) a brief summary of the steps to enlarge the image from here. Put the negative image in the magnifier until the positive image dries, and we will come back to explain each of these steps in detail in this section.
A good amplifier must have the following characteristics:
(a) The illumination shall be completely equal over all the area occupied by the sensitive paper. This can be verified by placing sensitive paper of a suitable area and exposing it to light for an appropriate period of time without placing a negative, then performing the display process.

(b) The amplifier should be easily raised and lowered without violence

(H) It should have a means to install the lighting house assembly, the negative holder, and the lens (which are the main parts) at the height we estimate, so that it is not subject to falling on its own during the exposure process.

(E) The lens covering power should be suitable for the negative area.

(e) It should be simple in its manufacture, so that it can be easily disassembled and installed without violence.

A brief summary of the steps to enlarge and display the image:

Below is a summary of the work steps, and we will talk about each of them in detail later

1- After showing and drying the film, the negatives are separated from each other, and the good ones are kept in an organized manner in special envelopes of a suitable size.

2- Before the enlargement, the glass of the negative holder is cleaned, and the selected negative image is placed in it, then the negative holder is placed in the magnifier.

3- After determining the required degree of magnification, the focusing distance is set. What is meant by adjusting the distance is to move the lens up or down so that the lens is far from the image. The negative is appropriate for the distance of the sensitive paper from the lens.

4- Since the exposure time of sensitive paper depends on many factors (such as the magnification ratio - the strength of the light source - the widening or narrowing of the lens aperture, the density of the negative image, the speed of sensitivity of the sensitive paper), so we must start with an initial experiment to estimate the appropriate exposure time) and we will We will explain this in detail in this section) and the experiment will be carried out on a piece of the same type of sensitive paper that we intend to use.

5- The sensitive paper with a suitable area is placed in its place facing the lens, and the exposure time is the time previously estimated in the previous step.

6- The image begins to be shown in the appropriate solution, and the duration of the display depends on the type of sensitive paper and the type of appearance. The duration of the recitation usually ranges between one and two minutes, and it may decrease or increase slightly according to some factors that will be mentioned later.

7- The exposing basin should be moved throughout the duration of the exposing process to remove what is likely to be present. of air bubbles on the surface of the sensitive paper and to ensure evenness of appearance on all surfaces. flat image.

8 - As soon as the duration of displaying the image ends and its color reaches the appropriate degree, it is immediately transferred to. Another basin with an acidic solution known as the stop bath would stop the display process immediately. The image is placed in the stop bath for about a minute or more.

9- The image is transferred to the fixing solution, and this process takes about a quarter of an hour.. However, the white light can be lit after about three minutes.

10- Wash the image in running water for about half an hour.

11- The process of drying the image begins with one of the methods that I will explain in detail in this chapter.