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: Paul Schilliger <email@hidden>
- Date: Thu, 07 Feb 2002 21:54:11 +0100
Marc,
Thank you for your in depth response to my question.
I better understand now why the different options are there and that they are not here merely to make life more
complicated for novices like me!
However, I just made some trials, converting an image of a bright, almost fluorescent purple violet azalea into SWOP
space using the different intents and options, and as usual, none seemed capable of preserving anything from the
original RGB colours! Of course this simply means that the four colour inks can't reproduce that tone, despite the fact
that the Epson CMYK inks can print it very well from the RGB file (this is still a mystery to me!)
Contemplating such colour loss on my screen, makes me think that the almost imperceptible changes from one intent to the
next seem futile at this stage and are probably visible on very high quality reproduction level only, which I wish I can
approach some day! Meanwhile I will have to be satisfied with prints of magenta Azaleas and blue Petunias!
With the printer however, the rendering intents differences are more visible and I will try use the best suited intents.
Thanks also for your explanation of the driver's work at converting on the fly to simulate an output device.
Paul Schilliger
email@hidden
Paul Schilliger wrote:
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Message: 7
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Date: Wed, 06 Feb 2002 16:04:14 -0500
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Subject: Re: What rendering intent for RGB to CMYK and for proofing on
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Epson RGB printer?
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From: Marc Levine <email@hidden>
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To: <email@hidden>
>
>
Paul,
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Regarding offset press production and ICC, the most important thing is
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typically tonal quality - you want the image to look as natural as possible.
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For this reason, I would use the perceptual rendering intent to transform
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images into the press colorspace. When transforming from RGB, you are
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typically transforming the image from a larger color space to a smaller one.
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In order to map the colors correctly requires gamut compression. I think
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that most people will understand that the press will not reproduce all of
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the monitor colors. What they will not understand is why the tonal quality
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of the image is degraded. Using the perceptual intent will help to preserve
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the tonal quality as much as possible by diffusing the gamut compression
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into the image.
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In general, a first print should use perceptual as it give the most natural
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look to an image. Once an image has been produced, and users wish to
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simulate the output on another device, the Relative Colorimetric intent
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should be used to accurately replicate the specific content of the original
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print. In such a case, the original image has already been transformed into
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a smaller colorspace and should not suffer from breaks in tonal quality when
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transformed into the proofing colorspace.
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Once you understand this workflow, you can rearrange your process to suit
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your needs (Produce your proof prior to the press image for example). In any
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event, the most important thing is to understand the needs at different
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stages of the workflow and use the appropriate settings.
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Regarding the use of the Saturation intent - this is the probably the least
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used intent in the industry. This intent primarily is used to create impact
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when rendering corporate graphics. The intent is less concerned with tonal
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preservation or color matching - two big issues in reproducing images.
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Lastly, the whole deal with Photoshop driver extension allows you to perform
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the same functions available from the image/mode menu (assign/convert) after
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the fact. The source space lets you assign the current document profile -
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choose "document" to produce an image that most closely resembles the
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screen. Selecting "proof" instructs the driver to produce an image that
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reflect the output of another device. As in the above example, if you have
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previously printed the image data on a different device and you want to
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simulate that output, you would specify that device in this menu. This
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method should produce a less accurate image to the screen as it incorporates
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the limitations of both the proofing device (destination) and the simulation
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device (source).
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One more thing, always leave BPC off. Turning it on will remap your output
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vales from those specified by the profile. In my experience, the color
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content of the image changes considerably due to additional processing by
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photoshop. Leaving this unchecked transforms color based only on the profile
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and should give you a clearer impression of your profile's capabilities.
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>
-Marc
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--
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Marc Levine
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Monaco Systems
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Technical Manger
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Sales Division
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www.monacosys.com
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