Shutter

The only cameras that do not need a shutter are digital cameras (they simply turn on the CCD when necessary), and pinhole cameras (exposure times are so long that you can use a hat or a hand as a shutter).

Shutter characteristics are:

• Its exposure range, that's to say, the distance between the minimum and the maximum exposure time.
• Its precision and repeatibility.
• Its lag, that's to say, the time (usually measured in milliseconds) between the moment you actuate the shutter, and the moment it actually starts to open.
• Its step, that's to say how small the step between the times it can deliver. A mechanical shutter usually works by factors of two: one second, one half, one quarter, one eigth... Electronic shutters can be controlled with great precision, and they can be nearly continuous. In practice, they typically have a step of 1/3 of an f-stop

Mechanical shutters obviously don't die on you when the batteries end, but this is less of an argument now that modern cameras are completely slave to the batteries (most modern SLRs cannot even advance film without batteries).

Shutters can be further divided into leaf shutters and focal plane shutters.

Relevant writeups: synchro X, B, T, shutter speed.

Shut"ter (?), n.

1.

One who shuts or closes.

2.

A movable cover or screen for a window, designed to shut out the light, to obstruct the view, or to be of some strength as a defense; a blind.

3.

A removable cover, or a gate, for closing an aperture of any kind, as for closing the passageway for molten iron from a ladle.

© Webster 1913

Shut"ter, n. (Photog.)

A mechanical device of various forms, attached to a camera for opening and closing to expose the plate.

© Webster 1913