Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!crdgw1!uunet!visix!andrew
From: andrew@visix.com (Andrew Bernard)
Newsgroups: comp.lang.postscript
Subject: Re: Another setscreen question
Message-ID: <1991Apr17.194643.24548@visix.com>
Date: 17 Apr 91 19:46:43 GMT
References: <91106.223452CXT105@psuvm.psu.edu>
Organization: Visix Software Inc., Reston, VA
Lines: 29

In article <91106.223452CXT105@psuvm.psu.edu> CXT105@psuvm.psu.edu (Christopher Tate) writes:
>Is there any difference between, say, a 106 dpi gray screen and a 100 dpi
>screen?  Or a 53 dpi screen and a 55 dpi one?
>

This depends on the device.  There's only so many ways a given halftone
pixel can be tiled over a bitmap to give a pleasing result.  The larger the
spot is, the more it can be shifted around to produce different angles.
The spot size is inversely proportional to the halftone frequency.  This
is a considerable simplification of what goes on inside the RIP.

>Don Lancaster spoke in his column in Byte magazine last summer about the
>"secret" gray map of printers, and (to me, at least) implied that there
>were only so many distinct combinations of resolution and angle that the
>printer can produce.  Apparently there's some way of investigating that
>"secret" gray map, since Lancaster provided a diagram intended to represent
>it for a LaserWriter II.
>

There is a program which will reproduce the possible spot shapes for a 
PostScript printer, given a certain frequency.  It's available in one of 
the more advances PostScript books, but the title eludes me.  Can anyone
help me out here?  It's the one with the A-Z letter poster.

-- 
     andrew bernard              ring the doorbell on your mind  
    software engineer            but it's locked from the outside
     visix software                                 -dinosaur jr.
    andrew@visix.com