2007-11-08 00:21:28 · 2 answers · asked by Anonymous in Consumer Electronics ➔ Cameras
From Wikipedia:
The tube contains no optical elements; its sole purpose is to move the lens farther from the film or digital sensor. The farther away the lens is, the closer the focus, the greater the magnification, and also the greater the loss of light (requiring a longer exposure time). Lenses classically focus closer than infinity by moving all optical elements farther from the film or sensor; an extension tube simply extends this movement. When a lens is focused at infinity, its maximum magnification is the length of the extension divided by the focal length of the lens.
2007-11-08 00:58:32 · answer #1 · answered by anthony h 7 · 2⤊ 0⤋
An extension tube is simply a spacer used between the lens and camera body. It allows you to get much closer than the normal minimum focusing distance of the lens you're using. I've used them on a 200mm lens with good results.
The best extension tubes are fully meter-coupled. Buy the ones offered by your camera manufacturer.
2007-11-08 00:59:29 · answer #2 · answered by EDWIN 7 · 1⤊ 0⤋