Description
Telemeter
The original meaning of telemeter, and still one of the primary uses of the word, was a device used to measure distances to remote objects, that is, a rangefinder. Initially optical devices used in surveying, they soon found military applications in rangefinding, especially naval gunnery.
Rangefinder camera>
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. The lens is focused correctly when the rangefinder images fuse, compared 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.
