آلات التصوير ذات الظهر المتأرجح وقاعدة العدسة المتحركة .. كتاب آلة التصوير

Chapter Nine

Cameras with swing back and movable lens base

Due to the distortion of the perspective of photographs from distortion sometimes as a result of placing the camera in a low, high or side place in relation to the objects being photographed, which is necessitated by the nature, size and circumstances of photographing these objects. In view of the need to increase the depth of field in some cases beyond the maximum limit allowed by the narrowest aperture of the diaphragm, especially if the shooting is close-up. Therefore, the factories that produce cameras have endeavored to design cameras with bellows in particular that would overcome the previous problems.

The most important feature of these machines, which are usually called Technical Cameras, is to make the back of the machine that holds the sensitive film swinging by increasing the length of the blower on one side than the other (Fig. 127). The base of the Lens Standard is also designed so that it can be slid to the right or left in relation to the middle of the image, or tilt the lens forward or backward, or raise it up or lower it down relative to the middle of the image as well (Fig. 127).

The design of the previous form differs from what is usual in normal cameras, in which the surface of the sensitive film is completely parallel to the surface of the lens, and in which the optical axis of the lens passes through the middle of the negative image exactly, forming a right angle with its surface.

Here we summarize the most important advantages of using this type of machine (1):

(a) To increase the depth of field beyond the maximum allowable by the machine if it does not have a swinging back or a moving base (Figs. 128, 129, 130).

(b) To control or exaggerate the perspective so that the near objects appear very large in relation to the distant objects that appear very small, in addition to the depth of field (Fig. 129).

(C) Correcting the error in the perspective of images of objects with vertical, parallel sides (Figures 132, 133, 135, 136, pages 256 to 259).

(D) Combining the images of the front and side planes together in the images of parallelogram bodies, while maintaining the parallelism of the horizontal sides in the front plane (Figures 146, 147, p. 266).

(e) Obtaining images in which a frontal view of the body appears despite the camera being placed sideways (Figs. 143, 144, 145, pages 264, 265).

The effect of using the swinging back in fixing the perspective of the image:

According to what we have already seen in (Fig. 128), the swinging back is used in close-up situations to increase the depth of field to a greater extent than it would be possible to obtain if the bellows did not extend in one of its sides.

Increasing the depth of field is not the only consequence of extending one side of the bellows more than the other, but it also results in an exaggeration in the perspective of the image (so that the near objects appear very large in relation to the distant ones, or the near end appears longer and larger in size than the distant one). Exaggeration in perspective greatly increases the forest if the photographic lens has a short focal length, and also increases the depth of field (Fig. 129).

And if the depth of field does not reach the amount that we hope for despite following all the previous methods, it is also possible to take advantage of the moving lens standard base by rotating it right or left around its vertical axis so that the extension of each of the surfaces of the objects being photographed, the film plane and the lens base plane are all gathered in one One imaginary point (Fig. 130).

The effect of using the moving lens base in increasing the depth of field differs from the effect of using the swinging back in performing this purpose, as changing the position of the lens as shown in (Fig.

We see in (Fig. 131) the effect of using each of the swinging back and the base of the moving lens in increasing the depth of field and the perspective of the image.