Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!tut.cis.ohio-state.edu!att!mcdchg!ddsw1!corpane!sparks From: sparks@corpane.UUCP (John Sparks) Newsgroups: comp.misc Subject: Re: Advice about light pens Summary: Watch out for black! Message-ID: <754@corpane.UUCP> Date: 3 Jun 89 18:04:52 GMT References: <1989May18.213756.22453@utpsych.toronto.edu> <727@xroads.UUCP> Reply-To: sparks@corpane.UUCP (John Sparks) Organization: Corpane Industries, Inc. Lines: 28 In article <727@xroads.UUCP> ronnie@xroads.UUCP (Ronnie Phillips) writes: >In article <1989May18.213756.22453@utpsych.toronto.edu> chris@utpsych.toronto.edu (Christine Hitchcock) writes: >>I'm interested in buying a light pen for an IBM AT with a VGA monitor. A light pen works by detecting the electron beam as it scans by the pen. As a result, it has one major drawback: It won't work on a black background or on a black color. black on a CRT is the absense of the beam (it's turned off) therefore the pen can't detect anything. It also has trouble with dark colors, especially dark blue. Also if you hold the pen even slightly away from the screen it will detect more scanlines than you might wish (think of it as a camera that is out of focus). Of course, if you are drawing with it, this can make some neat airbrush effects as the pixels drawn get randomly get drawn throughout the fuzzy focus area. The best type of input device I have used is a graphics tablet. With one of those you can even trace in things. The light pen is a good picking device for choosing points off of the screen. like in a menu type operation. -- John Sparks | {rutgers|uunet}!ukma!corpane!sparks | D.I.S.K. 24hrs 1200bps [not for RHF] | sparks@corpane.UUCP | 502/968-5401 thru -5406 If you've seen one nuclear war, you've seen them all.