720323w@aucs.AcadiaU.ca (Bill Wilder) (05/16/91)
I'm currently printing (Ventura Publisher - Windows) greyscale images on a 300 DPI Posctscript printer. This is fine for preview purposes. For final printing we send the Postscript text to an external 1200 DPI typesetter and we let the printer create halftones using whatever techniques they have. Final results are good. My question is how would the output look if the greyscale images were done directly by the Postscript typesetter? My scanner can do 300DPI with 16 grey levels so I recognize that an upgrade might be required at that end. Thanks very much for any comments. -- Bill Wilder Computer Systems Manager Kentville Research Station Agriculture Canada
bradlee@cg-atla.UUCP (Rob Bradlee) (05/17/91)
In article <1991May16.124711.1384@aucs.AcadiaU.ca> 720323w@aucs.acadiau.ca (Bill Wilder) writes: >My question is how would the output look if the greyscale images >were done directly by the Postscript typesetter? My scanner can >do 300DPI with 16 grey levels so I recognize that an upgrade might >be required at that end. Sounds like your output should look fine if you went straight to the typesetter. Why not send one page as a sample and see what the results look like? It should save you money not to have the printer stripping things together by hand (or else maybe they're already doing just what you suggest!). One gotcha might be that the printer is cleaning up the images at scan time (adjusting gray curve, etc.) which you might not have the software to do. But give it a try and let us know what happens. -- Rob Bradlee w:(508)-658-5600 X5153 h:(617)-944-5595 AGFA Compugraphic Division. ...!{decvax,samsung}!cg-atla!bradlee 200 Ballardvale St. bradlee@cg-atla.agfa.com Wilmington, Mass. 01887 The Nordic Way: Ski till it hurts!
gregd@hpgrla.gr.hp.com (Greg Degi) (05/20/91)
> My question is how would the output look if the greyscale images > were done directly by the Postscript typesetter? My scanner can > do 300DPI with 16 grey levels so I recognize that an upgrade might > be required at that end. You won't be happy with a 4bit (16 level) greyscale image rendered on a typesetter. Because of the large change in density (darkness) as a level changes by one count, pictures (particularly large areas of nearly the same density like faces) start to look like topographic maps. This "feature" is called contouring. For good results you need at least 64 levels of grey but in practice the next availible size is 256 levels. 300 dpi is plenty for having a typesetter generate the half-tone from greyscale information. You only really need about 1.4 times the screen size you are using (120 screen is pretty fine) so 300dpi is more than enough. Greg Degi Hewlett Packard