Operation and Repair of Cameras

Excerpt from the book

Adjustment of the Camera

Adjusting the "FED" and "Zorki" cameras involves two steps: first, the working distance of the camera is set, and then the rangefinder is adjusted.

The working distance of the camera is the distance from the upper plane of the lens mount to the support disk. The working distance of the lens is the distance from the lower plane of the lens mount to the focal plane, which is the plane located at the focus of the lens and perpendicular to the main optical axis. In the diagram (Fig. 63), the "Industar-10" lens is shown. The NN1 line passes through the center of the spherical surfaces, with the main optical axis. The F0 line is 50 mm, which is the focal length, i.e., the distance from the support disk to the center of the lens to the focus. The FM line is the focal plane. The MM1 line is the working distance of the lens, which is part of the focal length of the lens. The working distance of each lens is indicated in its passport. The working distance of the "Industar-22" lens is 28.8±0.02 mm, and the early "Industar-10" lenses were 28.3 mm. In recent years, the "Industar-10" lens has been produced with a working distance of 28.8±0.02 mm.

Special instruments are available in factories for measuring the working distance of the lens and camera. For this purpose, a photographer is recommended to make two fairly simple devices. The working distance of the camera is measured with an indicator (Fig. 64), which works with an accuracy of hundredths of a millimeter. Indicators sold in stores require some modification. First, a metal crossbar 1 (Fig. 65) should be made. The lower surface of the crossbar must be perfectly flat and polished so that it fits well on the lens flange on the camera body. The thickness of the crossbar should be 12 mm, and the width should be 18 mm. To secure the crossbar, drill a hole in it and put it on the indicator base. The crossbar is fastened with a screw 2. If you press down on the movable rod of the indicator, it will move up, then, if the finger is removed, the rod will return to its original position under the action of the spiral spring 4 (Fig. 65) inside the indicator mechanism.

The distance between the lower end of the rod and the lower surface of the indicator crossbar should be approximately 30 mm. The indicator needle should be at zero. It is also necessary to adjust the spring force that returns the indicator rod to its original position. The fact is that the indicator rod, when measuring the working distance of the camera, rests on the support disk 25 mm, under which there are two relatively weak ribbon springs. To measure the working distance of the camera, the indicator rod should not depress the support disk. This can only be achieved if the indicator spring is weaker than the springs under the support disk.

The indicator spring 4 cannot be adjusted and must be removed completely. In addition to the spring 4, the indicator mechanism has a hair spring (spring 5), which regulates the smooth movement of the needle. The force of the spring 5 is sufficient to return the indicator rod to its original position (you need to ensure that the needle is in a vertical position during measurement).

To open the indicator mechanism, you need to unscrew the nut and remove the cover. The working distance of the lens is measured using a device that we will call a collimator.

Meisenberg Isaac Solomonovich

Operation and Repair of Cameras

(In Ukrainian language)

Editor R. Loseva

Cover by artist Z. Kukharenko

Technical Editor S. Shafeta

Proofreader T. Medvedeva