أجزاء آلة التصوير ٢-a .. كتاب آلة التصوير

6- A mechanical means to change the space on which the next image is recorded after clipping a previous image (Film Transport Mechanism): It is no more than a means of turning the wrapped film to make it completely flat when it falls in front of the lens.

7- Focusing:

The method of adjusting the distance differs in different cameras, and they all boil down to moving the lens forward or backward until the image becomes sharp. The process of adjusting the distance is actually an adaptation of the distance. In proportion to the distance of the object from the lens. If the object is located at infinity, the distance between the film becomes smaller until it becomes exactly equal to the focal length. Conversely, the distance between the lens and the film increases if the object is close (Fig. 10). Unless the distance between the lens and the film is adjusted to suit the distance of the body from the lens, an unsharp image will be formed, so that the light points emanating from the body are not represented in the form of points of light either on the film, but are represented in the form of circles of light mixed (circles of confusion). Figure 11).

The distance in the camera is set in one of the instantaneous ways:

(a) By seeing the image directly on the frosted glass (if the camera is prepared for that) and moving the lens forward or backward until the image appears completely sharp.

(B) By means of the numbers shown around a lens for Focusing Scale imaging (Fig. 12), after the distance has been estimated by looking, or by measuring if we want to be accurate.

(C) Using the telemeter (Fig. 13), if the distance adjustment in the instrument depends only on that graduated division surrounding the lens (Fig. 12), then the distance of the lens and the object must be estimated first, and then the lens should be adjusted according to this dimension. The distance estimator performs this work instead of relying on guesswork that may differ from one person to another. The shape of the distance estimator differs in different cameras. It may be a piece of the machine called a Telemeter (Fig. 13) or it is connected to the machine as part of it, but whatever its shape differs, all types depend on Based on one theory taken about visual perception with both eyes, and we can summarize it as follows:

When the eyes look at an object that is a certain distance away from them, the two lines of sight will converge at a point located on the surface of this object. And confined between the lines of sight is an angle that becomes wide if the body is close to the eye and narrows whenever the body is far from it (Fig. Hence, we find that the difference in the angle confined between the two rays is the means upon which the distance determinant relies in estimating the distance between the lens and the object.

In some types of (distance estimator), you see a double image as long as the distance is not completely set (Fig. b) In other types, you see the image divided into two halves, and by moving the lens, the two halves fuse when the distance has been set completely.

The numbers indicating distances are linked to other numbers indicating the depth of field (which is shown in the bottom row of Figure 12) and is called the Depth of Field Scale. We will come back to explain its purpose in detail in the section on this topic.