Light pens?

Peter C. Wallace pcw at
Sat Mar 19 11:03:27 CST 2005

On Sat, 19 Mar 2005, Pete Turnbull wrote:

> 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

Also, light pen software can create a moving lighted spot for the pen to 
track over dark screen areas...

Peter Wallace

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