Light pens?

[Pete Turnbull]

On Mar 19 2005, 11:19, GManuel \(GMC\) wrote:

> It must be able to somehow. I have used a light pen on a Commodore 64
with a
> Graphics Program called Picasso's Revenge and have drawn on the
screen with
> it even on a completely black background. Not sure how it does it
though.

It's just a question of sensitivity.  The black portions of the screen
are rarely quite black, because the electron beam is not quite turned
off.  Thus a suficciently sensitive lightpen can still detect the spot
as it scans past the pen's location.

-- 
Pete						Peter Turnbull
						Network Manager
						University of York