Re: Spectrophotometer measurements
Re: Spectrophotometer measurements
- Subject: Re: Spectrophotometer measurements
- From: bruce fraser <email@hidden>
- Date: Tue, 9 Jul 2002 19:57:47 -0700
At 5:00 PM -0600 7/9/02, Dan Reid wrote:
My understanding is the black table of a SpectroScan was designed to for
thin papers like newsprint. If you have the white table instead you
definitely need blank sheets OTW your L* will be off. On the flip-side
lighter colors and highlights may measure in accurately too because of the
black backing. I think the black table is based on an ISO standard, Henrik
may have words on this. Have you tried building a profile with a black
table?
Standards organizations like to measure over a consistent background
so that they can compare measurements. The problem is that when you
measure thin papers over black, you get a lower white point than the
viewer typically sees (unless the other side of the paper is covered
with black ink). It's not a huge problem on the output side, but it
really screws up the device-to-PCS tables and gives you an even
nastier soft proof than the accurate one would.
Measuring over a stack of blank sheets doesn't let me compare the
press data with FOGRA or SWOP standards, but it produces a profile
whose soft-proof is closer to the experience of the viewer than one
measured over black, without having to do a ton of profile editing.
Lining up printed sheets together may give you inaccurate measurements since
you're measuring through 2 or more thin papers will ink applied. I think the
saturation will be off. You should be able to easily *measure* this with the
Gretag MeasureTool as you've said.
Saturation and lightness both. It's not a good idea!
I always, if given the option, use several sheets of the same paper taped to
the SpectroScan table. Best if they can send some blank sheet too instead of
kludging it.
Me too, unless I'm trying to compare a press to a published standard
that was measured over black.
B
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