كيف يعمل الفيلم باك ( رزمة الفيلم ) .. آلات للصور الفورية .. كتاب التصوير الضوئي

How film pack works .. Instant photo machines .. Selection and use of materials .. Book of photography

How film pack works

The negative and positive surfaces are located separately in a chassis located at the back of the machine. The sticky detector is located in pods inserted between the negative and positive surfaces. When the sandwich comes out of the machine between two internal rollers, the pods explode and the appearance is spread evenly over the negative.

There is a pack of eight negatives applied to the chassis frame with a pressure plate and behind the plate there is a similar pack containing eight positive images. Each negative is covered with a black paper on it or is pulled out of the machine before the picture is taken.

After exposure, i.e. taking the picture, we pull a sling first, which places the applied negative image against a positive image and pulls out a second sling. The film can remain in this position until the next operation.

When we pull the second tongue, the captured negative image and its combined positive image pass between two pressure rolls (rollers), so the pods containing the developer explode and the sticky developer material spreads in a thin layer between the two surfaces. The sandwich comes out of the machine and then we start the processing period which lasts several tens of seconds. The unimprinted silver salts in the negative image move to the surface of the positive image where the image is formed. After separating the two surfaces, we throw away the negative image.

1 - The machine
2 - The film package
3 - Pressure plate
4 - Rolls
5 - Detector
6 - First film
7 - Second film
8 - Negative ready for exposure
9 - Spare negatives
10 - Spare positives

- Instant photo reflex machine:
This single-lens reflex machine is very complex: all its operations are secured by a flat battery with a liquid electrolyzer contained in each package. Before exposure (above) the light reflected from the subject enters through the lens and is then sent by mirrors to the collimator where other mirrors transmit the image towards the magnifying eyepiece for viewing. The image is seen in its correct position and in the appropriate framing.

When we press the button (below) the mirrors change their position so that the image is now reflected downwards and formed on the film. At the same time a silicon cell measures the illumination of the subject and commands the electronic shutter for the correct exposure. The motor in the machine pushes the exposed film between two rollers, which causes the processing materials to explode (preserve) and spread within the multiple layers of film. The image is ejected from the machine and processing begins.

- Types of films:
The classic instant film comes out of the machine in a sandwich form: the negative image is stuck to the positive image face to face. After a processing time of one minute, we separate the positive image - which we keep - from the negative image - which we throw away - the black and white positive negative film gives at the same time a positive image and a transparent negative image that can be kept. After processing (30 seconds at 21 degrees Celsius), we separate the positive image from the negative. The latter must be lightened in a solution of sodium sulphite at 12% and then washed before drying. There is a special basin that can be used for lightening.

The film used in the reflex machine (or its non-reflective derivatives) is completely different: the processing is automatic and is done automatically after the image is ejected from the machine. The sensitive surface is protected from light by a substance that gradually fades as the image is formed.

- Automatically processed instant color film:
As soon as the film (turquoise in color) is ejected from the front of the machine, the image begins to appear and its density increases rapidly, and the image becomes fully visible within a few minutes.