jad@dayton.UUCP (J. Deters) (05/30/90)
> Article <1873@xn.LL.MIT.EDU> From: tj@XN.LL.MIT.EDU (Thomas E. Jones) >Greyscale on low-end 300 bpi devices have a large "grain" size that >makes them photocopy *GREAT* on any lousy photocopy machine. On the >nice typsetting devices this grain gets very small, so the resulting >original looks much more greyscale, and less half-tone, but you can't >photocopy this well. Is there any way to manipulate this? I know >a Apple Laserwritter can't be made to have a smaller grain size, but >can the typsetting machines be made to have larger grains on half-tones? [...] >Going the other way, I suppose we could make larger grain sizes on a >1250 dpi typsetter by purposely making black/white images with large >grains, but this would be painful and awkward. > >Has anyone tried either of these two methods? >tj@xn.ll.mit.edu or tj@ll-xn.arpa (one of these should work) >Thomas E. Jones, home (617) 924-8326 work (617) 981-5093 The "grain" you notice that copies well vs. the grain size that doesn't is used extensively in the engraving business. Examine your next payroll check, or any 'business' check or gift certificate you receive. Most of the modern checks have "check protect" features designed to enhance this effect on a copying machine. The payroll and accounts payable checks where I used to work came printed on stock that had the word VOID written across the face in a different halftone pattern. To the naked eye, the face of the check was simply patterned with horizontal lines. Closer examination showed that most of the lines were pastel solid yellow, whereas the word VOID was superimposed over the face in a larger grain size. Our current gift certificates here have more than three (!) such devices embedded in the face. One of the cute tricks they use is to print "DH" using narrow vertical lines over a circle of horizontal vertical lines of the same width. Either copiers can't discern the two dimensions equally, and therefore highlight the word, or they can't resolve the fine lines and only print a black circle. I've never really had the time to play with this in PostScript yet, so I'm afraid I can't post an example of such. Knock yourself out. -j -- J. Deters +---------+ INTERNET: jad@dayton.DHDSC.MN.ORG | S H * T | UUCP: ...!bungia!dayton!jad +---------+ ICBM: 44^58'36"N by 93^16'12"W "Vanna, I'd like to buy a vowel."