What is a rangefinder camera?

The letter M stands for a traditional rangefinder camera. Rangefinder cameras do not have a swivel mirror and prism viewfinder such as SLR cameras. Due to the smaller focal length between the sensor and the rear objective lens, the lenses of the rangefinder cameras are very small. It is possible to produce lenses with a very high image quality. The principle of distance measurement exists in the rangefinder camera for almost 60 years, so that older lenses can be used with new, modern cameras. In the range finding, incident light is used for focusing in the viewfinder window (1) and on the small rotatable mirror located behind the adjacent viewing window (2) of the rangefinder. In the viewfinder center, a small and brighter measuring field is projected. The brightening is directed via mirrors from the adjacent view window into the viewfinder. Behind the adjacent view window is still a rotatable mirror, which also projects a virtual image in the viewfinder, which shows depending on the mirror position a horizontal offset and characterizes the blur. The rotational movement between the mirror and the distance adjusting ring of the lens takes place mechanically via a cam roller and cam track. The cam roller is part of the camera and the cam track is located on the tube at the back of the lens. Vertical, offset lines of the same object origin from the viewfinder image and from the virtual image generated by the rotatable mirror are brought into coincidence via the distance setting ring of the objective. This distance measurement can only be used with lenses that have a corresponding cam track on the tube. The optical distance measurement is extremely fast and accurate, it works without camera electronics and can be easily explained using a trigonometric model of thought. If the side length of a triangle and the angle between the triangle side and the hypotenuse are known for a right-angled triangle, the length of the second triangle side (the distance to the object) can be calculated. The known length of the triangle is the distance between the viewfinder window and the adjacent lookout window of the rangefinder behind which the rotatable mirror is located. The rotational position of the mirror defines the angle of the survey triangle.

The camera has 2 additional electronic setting aids for distance measurement, so that even foreign lenses can be used with an adapter: the digital magnification of the image and the application of "Focus Peaking" on the rear camera display (in Live View mode) or in the mobile electronic viewfinder (EVF), which is plugged into the flash shoe. For this, the picture on the respective display is enlarged by a factor of 5 or 10. Sharp contour edges on the object indicate a high contrast which is electronically converted to another color, e.g. red. The sharper the "red contour edges" become, the more perfect is the focus in the considered area. The EVF can be adjusted in its brightness. This allows the object to focus properly even in low light or in the dark. External flash units are connected via a connection bar attached to the camera base. The HSS TTL measurement is possible up to 1/4000 s. If the above hot shoe is not covered by the electronic viewfinder, the flash unit can of course also be connected here. Since the distance between the sensor and the object bayonet is greater in the case of SLR cameras due to the pivoting mirror than with this rangefinder camera, the rangefinder camera can use almost all lenses of SLR cameras if an appropriate adapter is available.

The camera only has an automatic exposure mode, the aperture priority, i.e. the aperture is preselected by the photographer and then the shutter speed is set automatically by the camera. If you want to work with a certain exposure time, the aperture must be adjusted manually using a light balance. With continuous shooting 3 frames per second are possible. Video Full HD mode records 25 frames per second with 1080 x 720 pixels. The sound level is tracked automatically or manually during recording. All images can be alternatively recorded in color or in black and white. Sharpness, contrast and color saturation can each be adjusted in 5 levels.

The image quality is in the foreground of the camera, it is determined by the quality chain, image sensor, image processor and lens. The new CMOS sensor used with specially shaped micro lenses over the photodiodes of the pixels and the small distance of the color filters to the photodiodes ensures that obliquely incident light rays strike the photodiodes largely vertically. The full-size sensor (24 x 36 mm) has 24 megapixels and does not use a low-pass filter. The color depth is 16 bits per pixel. There is hardly any noise up to ISO 3200. In conjunction with the high quality lenses, e.g. APO-Summicron-M 1: 2/50 ASPH (see picture) or the APO-Summicron-M 1: 2/90 ASPH, the camera has a brilliant image performance which is currently not achieved by any other full-frame camera. The rangefinder camera is not a camera for fast reportage in sports and hectic press conferences, it is suitable for the quiet, inconspicuous recording from the background without the noise of a folding mirror; it is strikingly compact and limited to the essentials. It is a camera for individualists who value the faithful reproduction of architecture, art, nature and technology. Which 35 mm camera already performs the white balance by means of a gray card? The camera is not for everyone, but more for the ambitious photographer who achieves good shots with the few, but the right settings.

Copyright © : Dr. Günter R. Langecker


Date: August, 2013

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