Re: What rendering intent for RGB to CMYK and for proofing on Epson RGB printer?
Re: What rendering intent for RGB to CMYK and for proofing on Epson RGB printer?
- Subject: Re: What rendering intent for RGB to CMYK and for proofing on Epson RGB printer?
- From: email@hidden (Bruce Fraser)
- Date: Wed, 6 Feb 2002 16:16:22 -0800
At 6:47 PM -0500 2/6/02, Marc Levine wrote:
Andrew,
There definitely is a lack of standardization regarding the perceptual
intent. And, when going to a wide gamut device such as a pictography, or a
lambda, you can get excellent results using either (and sometimes superior
results with Colorimetric). However, I think you would agree that when going
to a much smaller gamut device (such as an offset press as indicated in the
original posting) Relative Colorimetric can deliver unsatisfactory results
due to breaks in tonality. Maybe it's better to say that in high
gamut-compression transformations (RGB file to offset press, for example),
perceptual typically does a better job. And, in transformations with little
or no compression, relative colorimetric will typically do a better job.
With regards to BPC, it's easy to see that the data is dramatically altered
by checking this selection using the eyedropper. I use ICC Tools
ProfileViewerPro to check the internal construction of my profiles. You can
see that the reported data matches the data in Photoshop with BPC off. Maybe
it's just a personal thing, but I like knowing that my profile is the only
thing managing my color.
The reason relcol is is giving you unsatisfactory results due to
breaks in tonality is that you've turned off black point
compensation...
BPC will either do nothing, or will ensure that your source black is
correctly mapped to your output black. Without it, depending on the
construction of source and target profiles, you will either get the
same result as with it on, or you'll get plugged shadows, or no true
blacks.
The only time I recommend turning off BPC is for proofing transforms
where you want the proofer to simulate the black of a
lower-dynamic-range process. Other than in that specific situation,
I'd much rather make sure that my output uses the full dynamic range
of the device, and I really don't care if the profile gets help or
not...
Rendering intents are blissfully unaware of image content. Perceptual
rendering attempts to compress the source gamut into the target
gamut. To do so seamlessly, it has to step on all colors to some
extent. If you have an image that doesn't contain many significant
out of gamut colors, perceptual rendering does unneccessary gamut
compression where relcol+BPC does not. It's really an image-dependent
call.
My $0.02
Bruce
--
email@hidden
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