Key components of monocular camera

1. reflector: its function is to reflect the image used for framing to the focusing screen through the photographic lens; The reflector is a reflector with silver plating on its surface.

Glass quality (note that it is not like a mirror, but a reflection on the back of the glass, so try to wipe the mirror as little as possible when maintaining the camera, even if there is dust on the mirror, it will not affect the imaging), and the 45 hinge is in the mirror box. Before exposure, the function of the reflector is to change the light path and reflect it into the viewfinder, so that the operator can view and focus correctly. Before the shutter is opened, the reflector turns up to make way for the light path, then the shutter is opened and the light reaches the film plane for exposure. After the exposure process, the mirror immediately returns to its original position, that is, the instantaneous mirror.

2. Focus screen: the function is to check the focus. The focusing screen is equivalent to the ideal film plane, that is, the distance from the mirror to the focusing screen is equal to the distance from the mirror to the film plane. Fresnel lenses, usually ground glass, are used to focus rather than the film plane before exposure. When the focus is accurate, a clear image will appear on the focus screen. Due to the principle of optical reflection, the picture on the focusing screen is reversed from left to right, which can only be corrected by the five-sided viewfinder;

3. Pentagon viewfinder: its function is to correct the left and right reflections on the focusing screen, so that the image seen by the viewfinder is exactly the same as the direction of the scene directly seen. A pentagonal prism is usually cut and polished by a whole piece of solid glass, and then the outer surface (except the two surfaces connected with the focusing screen and the viewfinder eyepiece) is coated with reflective materials to form a specular reflection inside. The viewfinder has two main indicators: viewfinder magnification (viewfinder magnification for short) and viewfinder range. The magnification of the viewfinder refers to the ratio of observing the opening angle of the subject to the eyes through the viewfinder to directly observing the opening angle of the subject to the eyes, that is, the ratio of the size of the subject seen through the viewfinder to the size of the subject directly seen with the eyes. The magnification of framing is large, the viewing angle is small, and the scenery seen during framing is close to the original object, with strong sense of reality; The framing magnification is small and the viewing angle is large, so it is easy to see the panorama when framing. If the magnification is too small, it is difficult to observe the details of the object, which is not conducive to composition and focusing, and there is a great difference between the object and the image, which makes it very uncomfortable to take pictures. The magnification is generally less than 1X, mostly between 0.75 and 0.95 times. ..

Field of view refers to the ratio of the scene range seen through the viewfinder to the scene range shot by the bottom film, expressed as a percentage. Generally, the picture seen from the viewfinder is not completely the shot picture, but always smaller than the shot picture, generally 90% ~ 100%. Therefore, SLR only basically avoids parallax, and only the framing range of 100% can be called no framing parallax. Usually only professional models have a visual range of 100%.