ok - I have now learned how to spell instantaneously.

The above illustration is for a focal plane shutter, which is the most common type in use. By having a band of light crossing the sensor or film a very even exposure can be obtained, which would not be possible if all the sensor was exposed at once. For long shutter speeds the band is wide, for shorter shutter speeds the band gets narrower.

Message edited on: 05/17/2005 05:19

And every one said, 'If we only live,
We too will go to sea in a Sieve,---
To the hills of the Chankly Bore!'
Far and few, far and few, Are the lands where the Jumblies live;
Their heads are green, and their hands are blue, And they went to sea in a Sieve.

Edward Lear
http://www.nonsenselit.org/Lear/ns/jumblies.html