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: Marc Levine <email@hidden>
- Date: Wed, 06 Feb 2002 16:04:14 -0500
From: Paul Schilliger <email@hidden>
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Reply-To: email@hidden
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To: email@hidden
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Subject: What rendering intent for RGB to CMYK and for proofing on Epson
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RGB printer?
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Hi All,
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Is there a simple rule when converting a RGB scans to CMYK for offset
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printing? I think this is one of the rare places
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where BPC must be on, what about the rendering intent?
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Same when printing the CMYK image to an Epson for proof, what is the rendering
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intent that simulates the best the final
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offset print? It seems to me that *saturation* produces the best screen match.
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But maybe the offset print will not have
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such bright colours? I have remarked that other intents mix some black with
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solid yellow and dull it for instance.
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I'm also not sure of which option in the Epson window must be chosen for the
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source space: document: SWOP or proof
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format: SWOP?
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Thanks for any advice!
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Paul Schilliger
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www.paulschilliger.com
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Paul,
Regarding offset press production and ICC, the most important thing is
typically tonal quality - you want the image to look as natural as possible.
For this reason, I would use the perceptual rendering intent to transform
images into the press colorspace. When transforming from RGB, you are
typically transforming the image from a larger color space to a smaller one.
In order to map the colors correctly requires gamut compression. I think
that most people will understand that the press will not reproduce all of
the monitor colors. What they will not understand is why the tonal quality
of the image is degraded. Using the perceptual intent will help to preserve
the tonal quality as much as possible by diffusing the gamut compression
into the image.
In general, a first print should use perceptual as it give the most natural
look to an image. Once an image has been produced, and users wish to
simulate the output on another device, the Relative Colorimetric intent
should be used to accurately replicate the specific content of the original
print. In such a case, the original image has already been transformed into
a smaller colorspace and should not suffer from breaks in tonal quality when
transformed into the proofing colorspace.
Once you understand this workflow, you can rearrange your process to suit
your needs (Produce your proof prior to the press image for example). In any
event, the most important thing is to understand the needs at different
stages of the workflow and use the appropriate settings.
Regarding the use of the Saturation intent - this is the probably the least
used intent in the industry. This intent primarily is used to create impact
when rendering corporate graphics. The intent is less concerned with tonal
preservation or color matching - two big issues in reproducing images.
Lastly, the whole deal with Photoshop driver extension allows you to perform
the same functions available from the image/mode menu (assign/convert) after
the fact. The source space lets you assign the current document profile -
choose "document" to produce an image that most closely resembles the
screen. Selecting "proof" instructs the driver to produce an image that
reflect the output of another device. As in the above example, if you have
previously printed the image data on a different device and you want to
simulate that output, you would specify that device in this menu. This
method should produce a less accurate image to the screen as it incorporates
the limitations of both the proofing device (destination) and the simulation
device (source).
One more thing, always leave BPC off. Turning it on will remap your output
vales from those specified by the profile. In my experience, the color
content of the image changes considerably due to additional processing by
photoshop. Leaving this unchecked transforms color based only on the profile
and should give you a clearer impression of your profile's capabilities.
-Marc
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Marc Levine
Monaco Systems
Technical Manger
Sales Division
www.monacosys.com
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