[Openicc] New Topic: data to share

Kai-Uwe Behrmann ku.b at gmx.de
Tue May 17 02:32:31 PDT 2011

Am 16.05.11, 20:32 -0400 schrieb Scott Geffert:
> New Topic, Some data I would like to share:
> There is a lot of talk about color but too many conversations are based on outdated industry assumptions. Over the past several years I have captured original L*A*B* values from artworks from around the world. The collection is comprised spectral measurements of world famous artworks, rare photographs and pure saturated colors from contemporary artworks and objects. The collection even includes a handful of samples from the actual Liberty Bell. These are as real world as it gets.
> When we assume sRGB in any part of the imaging workflow we are essentially clipping many colors that most modern printers (and even displays) can reproduce. In fact, Adobe RGB clips about 10% of these very printable colors which to me is unacceptable. When you are discussing "internal" spaces or untagged spaces for "no color management" I would argue that sRGB is not the way to go and many feel that ProPhotoRGB is too large but eciRGBv2 is ideal. It is L* based, it has a 5000k white point and the gamut is large enough to at least this real world collection of color critical objects. Most importantly the space is near finalization as an ISO technical specification so it fits the goals of open source development. It kills me that people investing time into developing and hopefully improving upon the status quo do not consider that the current foundations of imaging were based on outdated CRT output-centric limitations of the 1980's.

We must assume something if a image has no profile assigned. So update 
your software to handle colour spaces and then make sure the profile is 
embedded inside the PDF. The colour conversion should directly occure from 
source colour space (your CIE*Lab, ProPhoto, native camera space or 
whatever) to the final device colour space of the printer. And finally 
take care of gamut clipping to behave intentionally. That later might be 
the harder part.

> It seems to me that we should avoid clipping colors too early in the 
> chain. Please no negative replies to this posting because I am only 
> sharing real-world information, there is nothing to dispute here. The 
> measurements were created using and EyeOnePro device and the samples 
> were plotted in ColorThink therefore anyone could reproduce a similar 
> experiment with other source objects such as leaves, flowers paint 
> samples, skin tones etc. I would be happy to share these spectral 
> measurements offline with developers that wish to put them to good use. 
> I cannot offer programming input, but no one in the industry (even 
> powerful companies like Adobe and Apple) have access to the data that I 
> am offering to share in the true spirit of open source.

If you would like to share a link to your spectral imagery and a Lab or 
your prefered colour space version that would be helpful.

> eciRGBv2 against sRGB

Btw. eciRGBv2 appears to be a small gamut on my main montior. The profiles 
for cameraRAWs, which I created, do all exceed that monitor already. So I 
can only agree to the idea to keep the source profile as long as possible.
Of course thats merely a customisation recommendation for a certain field 
of appliance like arts, professional reproduction and archival and nowhere 
a general rule.

kind regards
Kai-Uwe Behrmann
developing for colour management 
www.behrmann.name + www.oyranos.org

More information about the openicc mailing list