Re: Target Reference file
Re: Target Reference file
- Subject: Re: Target Reference file
- From: Terence Wyse <email@hidden>
- Date: Thu, 15 Jul 2010 14:07:59 -0400
On Jul 15, 2010, at 1:37 PM, david wollmann wrote:
>
> On Jul 14, 2010, at 1:03 PM, email@hidden wrote:
>
>>> Or am I falling victim to Myth #2? http://www.colorwiki.com/wiki/Color_Management_Myths_1-5
>>
>>
>> Exactly! :-)
>>
>> Device values are just that and nothing more...there's no particular EXPECTED behavior from a set of device values.
>
> Okay, the device values don't represent any particular device. They are just CMYK numbers without meaning until I take measurements and give them meaning.
Bingo.
>
>> Now if you were to compare your printer profile to a "reference" profile such as AdobeRGB, sRGB, whatever, you'd have something to compare to.
>
>
> In ColorThink I could look at both profiles in 3D and see how they match up.
> Is there something else?
> Would the Gamut Volume be something to base an "optimized" printer condition on?
A qualified "yes".....as long as you understand that gamut volume doesn't necessarily mean you have a larger or more "saturated" color gamut. Gamut volume is also affected by tone distribution or "linearization". IOW, a better tonal distribution can result in more achievable colors without actually "expanding" the boundaries of the 3D gamut plot. So gamut volume is both the outer boundaries or "chroma" as well as the tonal distribution within the boundary.
>
>> For that matter, the first printer profile you create could be a basis or reference to compare against if you're going to make further adjustments to the device such as linearization, channel ink limits, whatever.
>
> Using my first built printer profile as my basis for comparison almost seems like using the colorimeter for checking itself when building a display profile.
>
> So lets say I have profile #1, then I decided to change the Ink threshold for Cyan. I relinearize, print new targets and build profile #2. In MeasureTool or ColorLab I compare the measurements of #1 to #2 and it gives me Delta E values. How do I know if profile #2 is better or worse? Sure there will be a difference but what would I look for in the numbers to show improvement?
I'm not really sure if Delta E values would tell you much in this context. It would tell you they were "different" but not which one is better. I would look at....1) gamut volume 2) gamut "boundary" 3) tonal distribution of the primaries/secondaries (change view to "points" in CTPro and 4) the "Curves" display and neutral analysis. The lower the chroma values along the neutral axis (using absolute colorimetric), the better neutral stability the profile should have.
I would go so far as to say that the outer gamut boundary size isn't all it's cracked up to be (or overrated). Even tonal distribution and neutral stability I believe are more important than outright color saturation.
>
> Who is to say that the first attempt was flawless, its just a characterization? After all I'm the one making VISUAL evaluations for ink bleed, pooling, paper cockle, etc. and then setting new ink restrictions.
Visual evaluation for ink bleed, etc., is a good thing but I also find that the neutral curves and chroma variation in CTPro are a good evaluation if you have the right total ink limit or not.
BTW, what RIP are you using? I've got a "cheat sheet" I've made for others that are specific to the ColorBurst RIP that you may find helpful.
Regards,
Terry Wyse
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