Re: Retrieving impossible colour from Lab


Henry Davis
 

Your last sentence is a doozy.

I believe the answer to where out of gamut colors go is: ‘away’ as in gone - but the numerical Lab values could be kept for reference in a duplicate of the Lab image.

If memory serves there is/was a Photoshop display option for displaying out of gamut colors as grey.

Reproducing out of gamut colors depends on the gamut of either ink or display as well as the illuminant. I believe even a plot or graph representation of a gamut will need the illuminant figured in as well. I suppose one could mix paint for a painting that would be entirely out of gamut for some methods of reproduction or even outside human perception - such as ‘invisible ink’, fluorescent colors or things that appear in infrared or ultraviolet. There are gamuts, and then there are some gamuts that are way out there.

There are lots of things we can’t perceive even though people have had a go at explaining what they would be like if we could. Humans have a different ability for hearing sound than animals. Animals also see differently than humans. Scientists try to demonstrate how animals visually perceive the world using odd-looking pictures. I’ve always thought those demonstrations fall way short for, by definition, human perception is not the same.

So, I wonder what you’re up to with this project. If you can say, what is the nature of the image you hope to produce (even if blank)?

Henry Davis

On Sep 8, 2020, at 7:13 AM, John Phillips <paulsimonrichards@gmail.com> wrote:

Hi, I am curious about what happens to out of gamut colours during an Lab - to RGB conversion - where do they go and is there a way to keep this information?

As I understand it, when a L*a*b image is converted to RGB, the colour values are clamped to fit into the 255 range, leaving legal representations of colours.

I wondered if it is theoretically possible to conduct this conversion and store on file only the data which is out of gamut, without the proxy colours?

Mr Margulis' work has inspired me for nearly 2 decades, I am an artist working on an experimental project and would like to produce files which are entirely out of gamut, with nothing visible to SRGB. Even if this means producing a blank image.

Thank you

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