Path: utzoo!mnetor!uunet!steinmetz!davidsen
From: davidsen@steinmetz.steinmetz.UUCP (William E. Davidsen Jr)
Newsgroups: comp.periphs
Subject: Re: plotter/digitizer/scanner ???
Message-ID: <8453@steinmetz.steinmetz.UUCP>
Date: 8 Jan 88 14:40:17 GMT
References: <161@umn-d-ub.D.UMN.EDU>
Reply-To: davidsen@crdos1.UUCP (bill davidsen)
Organization: General Electric CRD, Schenectady, NY
Lines: 28

In article <161@umn-d-ub.D.UMN.EDU> kmcmilla@ub.d.umn.edu (Ken McMillan) writes:
| 
| Could someone explain the differences between plotters, digitizers, and
| scanners? I understand how plotters work, but am at a loss as to how
| digitizers and scanners work. 

A digitizer will allow you to convert a line image to a series of
vectors. You (usually) manually place a crosshair mouse on the strating
point and click, then the end point and click. The {start,end} pairs may
then be processed.

A scanner (again usually) rasterizes a line drawing by moving a point of
light from left to right and storing data as a series of ones and zeros.
The the paper (or light) is moved down to the next "line" and the
process repeated. A good scanner produces about 300 dpi, the same as
many laser printers.

Some scanners, in hardware or software, allow grey scale by "dithering,"
or using a patters of dots to look like a shade of grey. Take a close
look at a newspaper photo and you will see this effect. It's sometimes
called "half toning," although I think a typographer might think there
was a difference. Using dithering reduces the resolution.

If a "real expert" wants to expand/clarify this, please do.
-- 
	bill davidsen		(wedu@ge-crd.arpa)
  {uunet | philabs | seismo}!steinmetz!crdos1!davidsen
"Stupidity, like virtue, is its own reward" -me