View Full Version : What is a rangefinder?
Can anyone explain to me what a rangefinder is?
In the Single Lens Reflex (SLR) camera the light passes through the lens and then reflects on the mirror, entering the viewfinder. At the taking stage the mirror is lifted automatically and the light is free to reach the film.
In the rangefinder type of camera there is a separate window which leads the light into your eye, so while pressing the shutter, you can still see what you are shooting.
A simple form of a rangefinder camera is a compact camera.
I hope this helped.
Well, the rangefiner itself is an optical device for determining distances based on principles of triangulation. Large ones were constructed for artillery and warships where accurate distances were needed out to thousands of yards. Smaller hand-held ones are available for hunters.
Even smaller ones, only a few inches wide, used to be made as accessories for cameras with just a simple viewfinder. These added an element of precision where one formerly just guessed at the subject distance and manually set that on the lens.
When the rangefinder is built into the camera, which is most common, it's mechanically coupled to the lens. Now you don't need to transfer the distance reading from the separate rangefinder and set that number on the lens focus scale.
Turning the lens focus ring rotates the lens barrel which is cut with a cam shape at the rear, which moves a swinging arm inside the camera lens mount. This pivots a small mirror in the rangefinder assembly by a calibrated amount.
The rangefinder is basically a way of looking at the subject from two different positions at the same time. On the front are two windows, providing these two views, separated a short distance called a baseline. The longer the baseline (the wider-apart the windows) the more different the two views of the subject, and the more accurate the measurement.
The rangefinder is usually integrated into the camera viewfinder. A half-silvered mirror or prism in the center gives a view of what the small RF window over on the right is seeing, superimposed upon the view straight through the main viewfinder window. The idea is that you see out-of-focus subjects with a double image, and you focus the lens until the two images overlap (coincide).
Rangefinders give more accurate measurements for closer subjects. This is fortunate, since at closer distances depth of field is more limited and you need more focusing accuracy.
While you cannot see depth of field directly with a rangefinder camera, it has the advantage of a bright viewfinder image and fast accurate focus regardless of the light level or lens speed.
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