[Openicc] New Topic: data to share

Scott Geffert scott at cdiny.com
Mon May 16 17:32:04 PDT 2011

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There is a lot of talk about color but too many conversations are based on outdated industry assumptions.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and hopefully improving upon the status quo do not consider that the current foundations of imaging were based on outdated CRT output-centric limitations of the 1980's.

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.

eciRGBv2 against sRGB
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The following Diagram shows the actual colors against ProPhotoRGB,AdobeRGB and eciRGBV2
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Scott Geffert

On May 16, 2011, at 3:00 PM, openicc-request at lists.freedesktop.org wrote:

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>   1. Re: Printing targets: App or driver ? (edmund ronald)
> ----------------------------------------------------------------------
> Message: 1
> Date: Mon, 16 May 2011 20:56:39 +0200
> From: edmund ronald <edmundronald at gmail.com>
> Subject: Re: [Openicc] Printing targets: App or driver ?
> To: "Alastair M. Robinson" <blackfive at fakenhamweb.co.uk>
> Cc: Open ICC Color Managment <openicc at lists.freedesktop.org>
> Message-ID: <BANLkTi=s5W4MKD1vxwmz9m+PV4NCDKT6Kg at mail.gmail.com>
> Content-Type: text/plain; charset="iso-8859-1"
> On Mon, May 16, 2011 at 7:56 PM, Alastair M. Robinson <
> blackfive at fakenhamweb.co.uk> wrote:
>> Hi,
>> On 16/05/11 18:14, Jan-Peter Homann wrote:
>> What is the advantage to profile the printer in RGB-mode, if gutenprint
>>> allows it to do in CMYK ?
>> Why enforce a colour space at all?  Encourage the use of one over another
>> by all means, but don't arbitrarily disallow a colourspace unless you have
>> *very* good reason.
>> It's much easier to create a good RGB profile than it is a good CMYK
>> profile; for an RGB profile there's just the three-dimensional colour space
>> to worry about.  For CMYK you not only have to sample four dimensions, which
>> requires way more patches, but you also have to consider total ink coverage
>> and black generation functions.
>> A good CMYK profile may give slightly better results than the canned RGB ->
>> CMYK conversion in the driver (in some cases maybe significantly better, but
>> Gutenprint's RGB->CMYK is pretty good), but the extra effort required to get
>> there will make it less likely that we'll be able to crowd-source profiles.
>> All the best
>> --
>> Alastair M. Robinson
> Yes, I did some experiments with CMYK profiles in the past, and got ok, but
> not superb results. On the other hand a handheld ColorMunki will do decently
> for RGB profiles, but in my opinion if you really want a good CMYK profile
> you need to read a few thousand patches and to do it reliably and without
> fatigue you should resort to scanning spectro; also the software may or may
> not be an issue. I have had good results with RGB profiles for Gutenprint,
> which are quite close to those supplied by Epson for the native drivers, and
> so I see no reason to introduce additional complexity at this stage of the
> project.
> Edmund
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