ما هي الكاميرا .. كتاب فن التصوير الفوتوغرافي .. اعداد د. محمد صعيدي

Camera

It is the ideal place to expose the film to a projected image of a specific subject. (Picture 2) represents a camera designed for amateur and professional use. It is a light-tight box inside which the film is.

In order to control the image projected onto the film, the camera has a lens which is an aperture equipped with a variable aperture diaphragm and a movable shutter to receive light for an appropriate period of time. These parts are essential to perform the following operations:

1- Project a clear image onto the film (lens). 2- Controlling the amount of light falling on the film (variable aperture diaphragm).
3- Controlling the time period for exposing the film to light (moving cover).
These three processes or conditions must be met in order to get a good picture, and we will discuss each of them as follows:

1- Project a clear image onto the film (lens).
(Lens)
Take a magnifying glass, or a reading lens, and put yourself in a room where the only source of light is a light bulb hanging from the ceiling or a window. Point the lens towards the light source (the lens is parallel to the source). Take a white sheet of paper and place it behind the lens parallel to it, i.e. the lens should be between the light source and the paper. Start moving the lens away from or near the paper, and you will get an inverted image of the lamp or window on the paper.

Drawing (3) shows how to form an inverted image of a subject by means of a simple lens, and we will explain later the lens in greater detail. If we encapsulate the part consisting of the lens and the inverted image, we get a camera or a camera.

If we move the lens closer or farther from the image, we get a more or less clear image, and this process is called focusing (focusing). A magnifying glass, or a large-angle lens, or a zoom lens. . etc. .

And what we call a lens is a number of lenses of varying concavity or convexity attached to each other. (Fig. (4).

2- Controlling the amount of light falling on the film (Diaphragme).

This is the second condition for a good picture.
In simple cameras, the light control aperture is fixed in size, and this facilitates the process of taking pictures, but this does not allow controlling the amount of light that the film is exposed to, and therefore does not allow the photographer to control the way the film is exposed to light.

As for the more advanced and complex cameras, the amount of light falling on the film can be controlled by means of a variable size aperture called (diaphragme) that allows the entry of a large or small amount of light as needed. The amount of light passing through the aperture is measured by (F-stops).

The veil of light works as the iris does in the eye. When we move from a dark place to sunlight, the eye needs time to get used to the intense light, i.e. the iris narrows its opening to limit the amount of light entering the eye. The opposite happens when moving from a very bright light to a place with little light. These processes are carried out by the nervous system involuntarily, in need of a veil with a narrowing and widening aperture. The lens of the camera is to regulate the appropriate amount of light to get a good picture. Photo (5) shows a lens that has opened its veil to its fullest extent, and photo (6) has reduced the opening of its veil to a large degree. .

3- The appropriate period of time to expose the film to light (moving shutter)
The time period of exposing the film to the projected light through the lens has a significant impact on the image quality. And the process of controlling that period is done by means of the moving shutter (Shutter), which opens and closes when the shooting button is pressed.
The movable shutter is of two types: the first type: the cover is located between the lenses that make up the lens, and it consists of interlocking metal sheets that open and close by pressing the shooting button, as we indicated above, exposing the film for a suitable period of time, which is determined by setting the closing speed of the curtain to the required time period. This period can be set between 1 second and 1/500th of a second.
The cover can also be made open as long as we keep pressing the shooting button, and it closes by leaving it free.

As for the second type, it is located inside the camera box directly above the film. It opens and closes automatically by pressing the imaging button.
From this type, it is possible to choose an exposure period of up to 1/1000 of a second, and sometimes less.