CHROMiX

Calculation of size of profile mismatch

Hello,

Is there a way within ColorThink to calculate the approximate number of colours or percentage portion of gamut difference between two gamuts? For example, Profile Inspector provides approximate gamut volumes for each profile. If I display a 3D graph of my print profile for a particular paper inside the graph of Adobe RGB, apply a solid colour to the print profile and reduce the transparency of the Adobe RGB profile, I can easily see the print gamut inside the Adobe RGB gamut and whatever portions of the print gamut which are not covered by Adobe RGB jut outside it. Is there a way to calculate the approximate number of colours included in the specific portions of the gamuts that jut out i.e. the sum difference between the two gamuts for each specific area of mismatch?

Words fail me. I hope this is clear. Thanks,

Paul

I understand you. It would be good to be able to calculate the area of two gamuts where they have the same volume in common - and also to calculate what portion is not common to both. This is a good idea. ColorThink Pro cannot do this now, but it is a good idea for a feature in a future version of ColorThink. I have gone ahead and added this to our feedback system. There is a way to submit a feature request, or a tech support question or even report on any bug that you find via the Feedback form that is built into the software. I know you know about this already Paul, but I’ll mention it for others reading this thread. Within ColorThink, go to Web > Feature Request / Bug Report.

I’ve already added this to our system, so you’ll get an email if we implement this in the future. Off the top of my head, I don’ t know how hard this would be to do - but like a lot of possible features, we will be influenced by how many people are asking for it… so every request like this helps. I know I have heard other requests for something like this before.

Thank you, Pat. I’m sorry there is no way to do this currently. But, I’m glad some good may have come from the query. The subject came up from a discussion about using ProPhoto RGB vs Adobe RGB as a photographic working space. While it has become popular to think that bigger is always better and all is well as long as the print gamut is covered, I personally don’t believe this with respect to this subject at least. My print gamut is larger than Adobe RGB in some yellows, oranges and blues. It would be helpful to know just how many colours are involved in each range that I can’t print (I suspect it is perhaps a few hundred) versus how many I can see while processing in ProPhoto RGB but not print - perhaps more than one million not to mention the huge number outside the LAB gamut. Thanks again for the quick reply. Take care.

Paul

One thing I’m curious about is how you would define your “specific portions of the gamuts that jut out” and more importantly, how would you delineate where the exact areas you’re interested in finding the “difference between the two gamuts for each specific area of mismatch” start and finish?

As an example, consider AdobeRGB and Epson SP3880 Premium Luster profiles - in the screenshot, you can see that the 3880 profile extends outside of the AdobeRGB profile in the bright(ish) yellows and also in the blue/magenta/purple 3/4 tone areas. But how exactly would it be possible to say where the start and end of the area is, which juts out?

I’m not sure I understand exactly what you mean when you say “not to mention the huge number outside the LAB gamut” when referring to colours in the ProPhotoRGB gamut. An ICC profile is essentially bounded by the Lab gamut/space, so how could any profile actually represent anything which is beyond the Lab gamut? Is it even possible for any colour to be outside the Lab gamut? There are definitely colours which can easily be represented by a Lab co-ordinate but which are absolutely imaginary and not at all possible in the real world or for any human to ever be able to not only see but not even possible to visualise or imagine.

Something like 0,128,0 or 0,0,128 are complete nonsense, really. How could anyone ever even comprehend a colour which is darker than any black ever imagined yet at the same time, a more intensely saturated red than any laser could ever hope to produce? Or a yellow, again more intense than anything in existence but simultaneously as dark as dark gets - the absolute absence of any light is what L=0 is representing.

But I’m just curious about those colours in ProPhoto which you mention are outside of the Lab gamut. Please explain :wink:

The profile comparison you show here is very similar to the mismatch that I get from an Epson 4900. With respect to “how exactly would it be possible to say where the start and end of the area is, which juts out,” Steve Upton describes the gamut sizes displayed in Profile Inspector under “Overview” as being an approximation. It is nonetheless a handy approximation. So, I was hoping for a similar approximation of the profile mismatch. For example a statement which would be helpful might look like this 22,356 colours in the 3/4 tone blue region are not included in the selected gamut which would be the Adobe RGB gamut. I’m not a colour scientist or a computer programmer, but, perhaps general LAB coordinates could be provided to encompass the mismatch area of calculation. I would think that it would be possible to identify the points at which the mismatches occur. From there the mismatched volume could be calculated. But, again, I am not a programmer and talk is cheap.

Regarding my statement re ProPhoto RGB about the huge number of colours outside the LAB gamut, it is my understanding that the LAB gamut is representative of the colours perceptible by human vision. It is also my understanding that the colour gamut described in ProPhoto RGB extends beyond this gamut in the blues and greens. Here is a quote from WikiPedia: The ProPhoto RGB color space encompasses over 90% of possible surface colors in theCIE Lab* color space and 100% of likely occurring real world surface colors making ProPhoto even larger than theWide Gamut RGB color space. One of the downsides to this color space is that approximately 13% of the representable colors areimaginary colors that do not exist and are not visible colors. This means that potential color accuracy is wasted for reserving these unnecessary colors. I am new to all of this. But, 13% of 2.9 million colours is a huge number of colours which can not be seen. Please correct me if I have misunderstood this.

In answer to your question: How could anyone ever even comprehend a colour which is darker than any black ever imagined yet at the same time, a more intensely saturated red than any laser could ever hope to produce? the first thing that came to mind was how can we imagine the blackness of black holes which apparently exists yet which are theoretically so dark and dense that they suck light into them. This is certainly beyond my capability or capacity to imagine.

Nevertheless, it seems to me that ProPhoto RGB is too big for too little possible gain in the realm of photography. What I would gain in terms of being able to see my entire print gamut would come with many more colours I would have to manage and still could not print.

Thanks for your help with this.

Paul