amr@rti-sel.UUCP (Alan Roberts) (06/18/86)
Hello, My organization has two Imagen laser printers, one of the older, wet-process, 240 dpi printers, and a model 8/300, dry-process, 300 dpi printer. We just brought up TeX on VAX/VMS and a translator for the Imagen, and seem to be having problems with the newer 8/300 Imagen. The problem surfaced when I was drawing some horizontal lines with LaTeX. The lines that resulted were longer than specified. The problem gets worse as the line length increases (i.e. a 5 inch line is 1/16 inch too long, a 6.5 inch line is almost 1/8 inch too long). Vertical lines are much more accurate. When I translated the same DVI file for our 240 dpi Imagen, the line lengths were accurate. I have checked the two versions of my translator, and the only difference in software I have is the setting of the resolution value (which is set correctly for both printers). I was still sure it was a software problem, until one of the Imagen gurus here built a test job which contained raw Impress commands to draw the lines. We ran the test to both printers, and suprise, the older printer was accurate, while horizontal lines on the new printer exhibit the same errors. I have had one comment to the effect that all printers using the dry-process Canon engine are showing this kind of error. Has anyone else had this problem? Is it possibly a firmware error of some sort (either Imagen's or whatever microcontroller runs the Canon engine) that I can hope to get fixed, or is there some optical/mechanical accuracy tradeoff made in going to the admittedly convenient print cartridge? We also have LaTeX documents which translate and print perfectly on the older printer, but mysteriously relocate sections of the page on the 8/300 (despite having more buffer memory on the new printer). This problem leads me to hope that its a firmware bug causing me grief. I'd appreciate hearing from anyone who has been down this path before. -- Cheers, Alan Roberts Research Triangle Institute (decvax!mcnc!rti-sel!amr)
henry@utzoo.UUCP (Henry Spencer) (06/25/86)
> The problem surfaced when I was drawing some horizontal lines with > LaTeX. The lines that resulted were longer than specified. The > problem gets worse as the line length increases... > Vertical lines are much more accurate. When I translated the same > DVI file for our 240 dpi Imagen, the line lengths were accurate. There is a known "problem" with the little Canon engine. The vertical resolution is determined by how far the paper moves between scan lines, which I think is a matter of gear ratios in the engine. So that's pretty much fixed. The horizontal resolution is determined by the dot rate at which the controller sends video to the engine. The "problem" with the engine is that the right video rate for horizontal=vertical resolution is almost BUT NOT QUITE equal to one of the standard crystal frequencies. So most of the controller manufacturers are lazy and use the standard crystal, even though the result is slightly wrong. I measure the resolution as 298.5/inch horizontal by 302.5/inch vertical on my LaserJet Plus. As they say, "your mileage may vary". -- Usenet(n): AT&T scheme to earn revenue from otherwise-unused Henry Spencer @ U of Toronto Zoology late-night phone capacity. {allegra,ihnp4,decvax,pyramid}!utzoo!henry