digital presses and vector graphics

[Chicago Press]

We are having a big frustration with digital presses and the way that some vector graphics print. As "old-timers" in this business, we are used to the way that vector graphics are rasterized at the resolution of the device (usually 2400 in the case of the filmsetters and platesetters we're used to), therefore they look much cleaner and crisper than line art that has been rasterized in Photoshop.

However, since we got a DocuColor 240 three years ago, we've seen many vector graphics that look very thickened and filled-in. We have resorted to rasterizing manually in photoshop to get an acceptable result. I figured it was this low-end device, and that it must not really be the resolution they said it was.

Now we are looking to get rid of the DocuColor and move into a higher-end digital press. However the tests sheets that we've run so far have the same problem!

I suspect that none of these devices are really the resolution the vendors say they are, because gradients are also stair-stepping. That problem was solved back in the 90s with PSL3 smooth shading and its 3,000+ levels of gray. My guess is that these devices are not really 1200 or 2400 dpi, and they can't do PSL3 smooth shading with its 3,000+ levels of gray because they don't have the resolution needed to produced that many levels of gray.

Can anyone explain what is going on? These RIPs must be doing something differently than RIPs for plates on press. No vendor has been able to explain. Does everyone out there routinely rasterize vector graphics in Photoshop for jobs going to a digital press? That seems really hard to believe.

I'd be happy to provide a sample file if anyone is interested in testing what we see here.

Thanks,
Tina DeJarld
Chicago Press Corporation

 

[Chicago Press]

A little clarification: When I say it's a resolution problem, I may be painting an inaccurate picture. The result we get is not jaggy bitmapped edges, but thickened lines and filled-in white spaces. If this was the days of imaging on film and I saw this result, I would know exposure on the imagesetter was way too high.

I have heard from a few others on another forum that they also have to resort to creating TIFs of some detailed vector art before sending to their digital press.

Can anyone explain what is going on in these RIPs? Even if there is no solution, I'd really like to understand.