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Chapter three movie

Film is that sensitive surface that receives light coming from outside the camera through the lens. As a result of the fall of light, chemical changes occur

The appearance of an image when acidification

Movie types

1- Black and white negative films, black and white paper images are given when enlarged

Colored negative films are given colored paper images when enlarged. Colored positive films (positive) are given light slides (slides) for display on a screen by means of a projector.

Infrared films, and there are two types of them: black and white and colored with unnatural colors. It gives pictures with instant films that give an instant picture within a minute of leaving it
Camera . Colored instant positive films like No. 3 but developed on the spot in a machine
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- Special films such as films for microscopic imaging - films for transfer and re-imaging - films for ultraviolet rays - films for imaging - X-rays, etc.

Speed ​​or sensitivity of the film

By this we mean that films differ in their sensitivity to light. Some require a large amount of light (i.e. a wide aperture, a large exposure time, or both) and some are highly sensitive, which requires a very small amount of light (i.e. a narrow pupil, a very fast shutter speed, or both). together) .

Film sensitivity is measured by the American ASA scale or the German DIN.

It was recently agreed that a unified international number, ISO, should be mentioned, and it will be expressed in the word ISO, which is the previous two numbers together, with ASA mentioned first. A film with a speed of 100 ASA is written as 100/21 ISO.

We note that a film with a speed of 25 ISO needs twice as much light as a film with a speed of 50 ISO, and this, therefore, requires twice as much light as a film with a speed of 100 ISO, and so on...
For photographers who still use the German DIN standard, we write this table showing the German number and its equivalent:
There are currently in the market color films up to 1000 ISO and these are used for shooting in low light without the use of flash

film scale

There are different sizes of films. The type of camera, and the most common of these sizes is 35 mm, for serious photography. While there is a size 110 or a disc (disk for beginners. There are sizes 120 and 220 for larger cameras that give a negative area of ​​​​4.5 by 6 or 66 or 76 or 96 cm. These are cameras preferred by professionals and advanced amateurs. There are other sizes on the way to extinction, such as the 126. There are other types of studio cameras that are found in the form of pages and not a wrapped reel.

Grains

Silver is the sensitive material in the film composed of granules of silver halides (halides of silver bromide salts - silver iodide - silver chloride).

The larger the particle size, the greater the sensitivity, and vice versa is often true. These granules have an effect in the case of enlarging the image. The higher the magnification, the clearer the granules will appear in the image. Therefore, when we choose the appropriate film, we must determine in advance the percentage of enlargement that we want, as well as the desire or lack thereof for grains to appear in the image.

Image sharpness

It is the ability to distinguish converging lines. The higher the film speed, the lower the image sharpness.

Contrast contrast

It is the difference between the light colors and the list in the picture. The greater the contrast, the greater the sense of sharpness of the image, even if this is only apparent