Manufactured between 1940’s and 1960’s by Voigtländer & Sohn AG of Braunschweig, Germany. Accessories, accessories—what would we photographers do without them! Here is a fine example. The accessory rangefinder was produced to complement to Vito line of cameras. Most of the Vito’s had a fine focusing lens, but no built in or coupled rangefinder. This little gem slipped into the “accessory shoe” (there—now you know how it got it’s name!) and provided the user with a split diamond image rangefinder which the distance could be easily read from and then set on the camera lens. The photo shows the user’s viewing side. The other side has two oval windows at each end for creating the rangefinder measurement.
The original meaning of telemeter, and still one of the main uses of the word, was a device used to measure distances to remote objects, that is, a rangefinder. Originally optical devices used in surveying, they soon found military applications in rangefinding, especially naval gunnery.
A rangefinder camera is a camera fitted with a rangefinder, typically a split-image rangefinder: a range-finding focusing mechanism allowing the photographer to measure the subject distance and take photographs that are in sharp focus. Most varieties of rangefinder show two images of the same subject, one of which moves when a calibrated wheel is turned; when the two images coincide and fuse into one, the distance can be read off the wheel. Older, non-coupled rangefinder cameras display the focusing distance and require the photographer to transfer the value to the lens focus ring; cameras without built-in rangefinders could have an external rangefinder fitted into the accessory shoe. Earlier cameras of this type had separate viewfinder and rangefinder windows; later the rangefinder was incorporated into the viewfinder. More modern designs have rangefinders coupled to the focusing mechanism, so that the lens is focused correctly when the rangefinder images fuse; compare with the focusing screen in non-autofocus SLRs.
Almost all digital cameras, and most later film cameras, measure distance using electroacoustic or electronic means and focus automatically (autofocus); however, it is not customary to speak of this functionality as a rangefinder.