An everset shutter is a type of in-lens shutter in which a single stroke of the shutter lever first tensions and then releases the shutter. Thus the shutter does not need cocking, and there is no separate cocking lever. The mechanism was simple and cheap, and is often found on less expensively-featured examples of cameras also available with cock-and-release shutters. Everset shutters do not offer very fast or slow speeds; a typical range is 1/25 - 1/100 second; some are I/B or I/B/T. The pressure required to operate the lever (and especially the variation in pressure during the lever's stroke) may give rise to a considerable risk of camera shake. There is also the risk of greater latency than with a cocked shutter (once it is cocked: however, Cassell's Cyclopedia of Photography of 1911 cites the speed of operation as one of the advantages of an everset shutter, since an opportunity may be missed with other shutters because of the time taken to cock the shutter).
The term suggests an originally proprietary name. The shutter on the Thornton-Pickard Weenie is engraved 'Everset'; however, the term is defined in Cassell's Cyclopedia without reference to any particular maker.
- Jones, Bernard Edward (ed.) Cassell's Cyclopedia of Photography. Cassell, London and New York, 1911. Reprinted 1974 by Arno Press Inc., with Introduction by Bunnel, Peter C and Sobieszek, Robert A. ISBN 0-405-04922-6.