زيادة الحساسية بعد التصوير .. كتاب الإضاءة والفلم

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Increased sensitivity after imaging

This method is a way to strengthen the latent image (1), so it is called Latensification, i.e. Latent Image Intensification, and it is obvious that it is done after the imaging process and obtaining the latent image. The sensitivity increases by one
Immediate means:

(1) Use of bathing solutions

(2) Vapor treatment

(3) Post exposure fogging

First - the use of bathing solutions

We have previously explained the action steps to increase the sensitivity by means of solutions, in the context of talking about hypersensitising before imaging (p. 142).

One of the following methods is followed:

(a) Using alkaline solutions such as Ammonia or Triethanolamine



(b) By some oxidation agents such as:

Potassium permanganate

Diluted nitric acid

Aquous sulfur dioxide dissolved in water

The latter has been used successfully.

(c) By a mixture of the following solutions:

1- Potassium meta-bisulfite, its concentration. (acidic).

2 - Sodium sulfite. Sulphite has a concentration of 85 (it is an alkaline solution), then the two solutions are mixed. In order to avoid the increase in fog, some drops of anti-fog solution are added, such as what is produced by Kodak factories under the trade name 1. Kodak Anti Fog No.

It is possible to install an anti-fog solution according to the following ratio: 1 unit of benzostriazol .... 30 units of water.

The process of increasing the sensitivity takes place after obtaining the latent images, by washing the sensitive film or plate for five minutes at 65°F (17°C), then removing the droplets of the solution attached to the surface of the film and drying it as we mentioned before. In order to obtain the best results, it is better to dry the film before performing the display operations and what follows them.

The sensitivity increase that takes place after obtaining the latent image compared to that which takes place before imaging has the following advantages:

1- The transactions that take place after obtaining the latent image enable us to benefit from the anti-halo de dye during imaging, in contrast to the treatment method before imaging, as this dye is removed during washing and before imaging.

2- In the case of treatment after obtaining the latent image, there is no need to rewrap the film in the wrapping paper. Rather, the display process can be carried out once the drying that takes place in complete darkness has finished.

Second: Increasing the sensitivity by using fumes to strengthen the latent image:

This method is known as Vapor Latensification, and it is done by following one of the following methods:

(a) Using mercury vapor to increase sensitivity:

A drop of mercury is placed in a glass container, next to which is the panchromatic film, in a completely airtight box. If the film is tightly wrapped around the reel, then its sensitivity will increase to about double in a period ranging from three to four days, and if the film is not tightly wrapped, then 48 hours will suffice for this purpose. The success rate according to this method increases after imaging than in the case of treatment before obtaining the latent image.

(b) By treating the sensitive film or plate in the fumes of some acids, such as formic acid or acetic acid, and it may be noticed that the sensitive film or plate becomes loose if the process is prolonged, and therefore it is not. Extend the evaporation time.

(c) Sulfur dioxide gas is used according to the following method. (It is an easy and successful method):

1- The film is rolled on a reel of a developing tank showing the developing tank spool after removing the cover.

2- It should be placed in a tight bell that does not allow harm. By penetrating through it and with it a bottle in which the following is placed after adding them, sulfur dioxide gas will rise:

25 cm of 10% acetic acid
25 cm of 10% sodium sulfite solution

3- After 24 hours have elapsed from the fumigation process, the display process and other subsequent operations can be performed, and the film will then have acquired the desired sensitivity increase.

(d) There is another quick way to increase the sensitivity by almost doubling, which is to put the panchromatic film in an airtight box as well, next to it a piece of cotton saturated with strong concentrated ammonia, and leave it like this for a period ranging from ten minutes, after which the film is taken and placed in the camera directly for use, then the film is shown In a sea for a period not exceeding hours after the end of exposure.

Third: Increasing the sensitivity by making a light fog after obtaining the latent image:
This method is known as Post Exposure Fogging, and we have already mentioned, in connection with the discussion about increasing the sensitivity by creating light fog before imaging, that this method is done by exposing to light with a small diaphragm hole, high shutter speed, and relatively strong light. A very weak light is used with a prolonged exposure time (Fig. 47), by exposing the film to a very weak light in a dark room for a period ranging between (30-60 minutes) by placing it about three and a half meters away from a standing green lamp with a power of (10 watts).

It is experiments that show the best time is suitable for each type of sensitive film, as the degree of its sensitivity to the colors of light rays varies. And the results that can be obtained from the treatment after obtaining the latent image are better than those that we get before imaging.

Fourth: Using a high energy developer solution:

This method is considered the best of the aforementioned methods for the following reasons:
1- Using it, it is possible to take advantage of the greatest possible degree of sensitivity of sensitive films or panels.

2- This method is easy to implement, and doing it does not require special preparation, whether in tools or chemicals that are unfamiliar in small laboratories, in addition to being the shortest of the aforementioned methods. This process can be summarized as follows:
It has been proven that by adding some materials to the show solution, such as adding hydrazine salts, the following results:
1- The degree of contrast increases a lot.
2- The sensitivity of the film increases with an increase in the chemical fog on the silver salts that were exposed to light or in contact with it. As for those granules that were not exposed to light in the first place, or that did not receive a sufficient amount of light, they are under exposed
These salts have no effect on them. Based on the foregoing, it is possible to make a display bathroom that fulfills our required purpose and consists of the following:
A - Normal (mitol - hydroquinone) show solution.
2- A solution of the following two donors:

(a) Hydrazine Dihydrochlorid

(b) Kodak Anti Fog Salt. No. 2
And we show the following the composition of the highlighting solution, which is composed of two parts that are mixed after their composition: Kodak Anti Fog. No. 2.