Difference between revisions of "Convertible lens"
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Revision as of 17:52, 25 July 2010
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| convertible lense's inscription: focal length 32cm for front part only or 15.3cm for complete lens set |
A convertible lens is a lens consisting of at least two separatable parts, each containing a part of the lense's elements. 100 years ago these lenses were a common option for photo amateurs to give a double or triple extension folding camera more versatility. The common lenses of that era consisted of a pair of lens tubes, one to screw into the back of an aperture/shutter-unit, the other to be screwed into its front side. Mounted that way the lens element groups of both lens tubes gave the complete standard lens, usable with single extension of the camera bellows. Mounting only one of the lens tubes meant to switch to a tele focal length which needed double or triple bellows extension.
Some modern compact cameras have a double-focus lens instead of a single-focus or zoom lens. In most cases the focus switch of such cameras shifts one lens element into (or over), or vice versa out of (or away from) the lens tube.
