Re: expanding output color gamut with extra colors
Re: expanding output color gamut with extra colors
- Subject: Re: expanding output color gamut with extra colors
- From: email@hidden
- Date: Thu, 8 Jan 2004 12:40:48 EST
In a message dated 1/8/04 11:27:24 AM, email@hidden writes:
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In recent posts questions were raised about the use of supplemental colors
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(orange, green, light cyan, light magenta, red, blue) particularly with
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regard to the effect on the color gamut. I would like to understand more
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about this.
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Okay...
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My comments in this post are probing the practice of addinga small number
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of colors to the basic CMYK process color set, as seen in output devices
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that use for example 6 or 8 colors. I am not asking about the practice of
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substituting entirely different colors for the basic process color set, or
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supplementing them with Pantone or other solid colors.
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Fair enough...
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Apparently there are two different reasons why supplemental colors would be
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added to the basic process color set.
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First - to expand the color gamut (example - to output more colors that
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match a larger range of Pantone or other solids).
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Second - to overcome deficiencies with current systems (example - with
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inkjet if the drop size is not small enough then the standard color dots
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used in light tones are too noticible - therefore the use of lighter inks).
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Correct... those are certainly the main reasons.
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Does this fairly summarize the reasons for the use of supplemental colors -
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or are there other reasons also. If there are other reasons, what are
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they?
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Well, one could make a case for reducing total ink (red ink will make a lower
total on reds than yellow and magenta, for example), or for tying in to a
proprietary brand (like Hexachrome) or reducing metamerism (technically color
shifting under varying viewing lights), by reducing the gap between component
colors, and simply by using less Yellow ink.
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If one has a legacy image file in a smaller color space (for example CMYK)
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it's understandable that further conversions of the file may never take
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full advantage of a larger color gamut.
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True of small CMYK spaces (most are device spaces and would qualify) as well
as small RGB spaces.
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I think of this as a situation
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similar to a legacy file that has already been heavily compressed by a
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lossy form of compression - the damage is done and saving in a lossless
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compression format at some future point won't undo the damage.
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Fair analogy...
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But if one were to create an image from scratch in a large gamut working
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space - and from that space could convert to an output space larger than
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CMYK - for example CMYKOG - would the preferred starting point be a Lab
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space, an RGB space, or something else?
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Well, Lab certainly has some theoretical advantages; but Heidelberg and
Linoscan have lost out to Adobe Photoshop and RGB workingspaces, so the
practical
answer is RGB.
C David Tobie
Product Technology Manager
ColorVision Inc
email@hidden
www.colorvision.com
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