Re: Creating a SWOP proof with an Epson
Re: Creating a SWOP proof with an Epson
- Subject: Re: Creating a SWOP proof with an Epson
- From: Graeme Gill <email@hidden>
- Date: Mon, 17 Jul 2006 12:43:16 +1000
Terry Wyse wrote:
You can see, in my bogus example, that at 2% the yellow ink has
effectively neutralized the optical brighteners in the paper causing it
to appear "colorless" or neutral. The argument goes that this will fool
the linearization application and foul up the linearization. In
ColorBurst's case, since they use chroma for linearization, this sort
of makes sense.
It's a pretty dumb application if it works that way.
If you take your measurements but then "zero" out on the media (add +3
L* and +5 b*), giving you relative instead of absolute values, it works
just fine....
Any sensible linearisation application will work this way.
So, unless I'm missing something, using relative readings to calculate
chroma (or whatever) would work just fine regardless of spectro
filtration.
I think there will be differences. The FWA effects depend on
UV light reaching the paper. A UV filter on the instrument
effectively stops the FWA reacting at all. Without a UV
filter the FWA will be active at Y = 0%, and will decrease in
it's effects as you add Y, because Y is filtering out the
blue & UV light from the paper. So I would not at all
be surprised if the relative curves from UV filtered/non UV
filtered are a slightly different shape, especially near Y = 0.
Now that in itself is no reason to choose a UV filtered
instrument over a non-UV filtered instrument. Either
curve is fine as a reference for a particular paper & printer
combination. But if you want to support both types of instruments,
you would probably need to offer two different references, one for
each type of instrument.
anyway. In all my years in prepress <slash> printing,
linearization/calibration is ALWAYS done relative to the substrate.
Yes.
My last argument "against" UV-cut spectros is based on visual
comparisons of proofs. In every case I've observed, it certainly
appears to me that the non-filtered spectro ALWAYS produced the
superior visual match as compared to taking the same measurements with
UV-cut filtration. For this reason, I've pretty much settled on
non-filtered measurements when going for critical color proofing
applications.
My preference is for non-filtered instruments is that by using the right
software, the level of FWA can be measured, and its effects on the reproduction
can be allowed for in the color management process, whereas with a UV cut
instrument, you have no way of measuring the level of FWA in the paper.
Graeme Gill.
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