Sat, 22 May 1999 21:49:38 -0400 (EDT)
In a message dated 5/22/99, PM 08:27:00, email@example.com
<<and I can tell you that imagesetters are calibrated for PERCENTAGE
DOT but NOT for density.
Hmmm.... the percent dot has a direct relation with density; if we are
talking about hard dot, theoretically as long as the Dmax is above 2.0 then
the difference should not make any difference. That is, 50% dot should
measure density of 0.30 (+base+fog) if the Dmax is above 2.0.
Of course, if the Dmax is really as low as 2.0, it could mean that the dots
are not that hard because each dot actually has a gradation from Dmax to
Dmin, but imagesetter's Dmax usually is above 3.0.
>> The density ranges all over the place, and as
the imagesetter runs, and the lasers heat up, it changes.
I find this interesting and curios. It sounds like the dots are not hard.
>> The change in
density will not effect the percentage dot values (as used in offset
printing) hence it is of no concern to printers. HOWEVER, the density IS
important for alt-photo work because the negs print as a hybrid. >>
Yes, but it shouldn't matter that much (I am assuming that the alt. photo
worker can still make minor adjustment based on the densities; that is, I
don't believe that one can trust than every time you go to a service bureau
you can get an exact density values so one does not even need to measure. I
think such is almost impossible. I can only achieve that with film recorder
processed in the same chemistry on the same day (or within 2-3 days).
But maybe I haven't used imagesetter output that much. The reason I thought
it should be consistent was because of the theoretical calculation and my
experience with my imagesetter. For some reason, I don't think the service
bureau is maintaining the calibration well (this is the one that closed down
recently). In fact, he didn't seem to understand the concept of calibration
that much, yet his output is reasonably consistent.
Do you use stochastic screening or traditional halftoning?
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