The Hitchhiker's Guide to Digital Colour

Absolutely flattered that you have found any of this useful.

As you have probably discovered, the amount of reliable information of sufficient utility out in the wild is horrifically buried under layers of nonsense, numbers, and often times blind appeals to authority. Couple that with the fact that every single curious mind comes at the subject from a different vantage, and can stumble or get hung up in unique ways. This makes it incredibly challenging to suggest a single book or resource.

Worse, software largely is a mess. Plenty of things are brain wormed with some of the protocols peddled by the massive studios and corporations, or algorithms that are totally busted up rubbish. None of it works. Most of it is nonsense.

The main thing that one can do to insulate themselves from the confusion miasma is try to build up a nuts and bolts understanding. I’d be so bold as to say drawing a distinguishing idea between a “stimulus”, versus a “colour”, is an absolutely gargantuan step to sniffing out garbage. If we firmly locate the creation, perception, and understanding of colour as something that is generated in the human perceptual system, it allows us to immediately second guess nonsense that juggles numbers around, or treats electromagnetic radiation as colour.

To that end, I can think of perhaps no better singular tome to at least get one thinking in the right direction than Ralph Evans’ “The Perception of Color”. While it can be incredibly expensive to purchase a hard copy, there are rumours of a PDF lurking out in the interwebs.

I would be absolutely remiss to not also link you to Dr. David Briggs’ site http://www.huevaluechroma.com. Not only does Briggs cover things in a very observer-image-author vantage, his work covers very contemporary explorations of many often overlooked concepts. It also helps to expose readers to the various models, as well as practical examples to showcase how incredible some of all of this is.

Those are probably two very good entry points to round out understanding, and from there, it can be easier to lift one out of the quagmire of number fscking.

Remember… literally no one on the planet understands how our vision works! Also remember that a majority of the research up to around 1985, often times funded by Kodak, was done using tools that are eclipsed several thousand times over by the device you are reading this on. Their wisdom came from experience and insightful thought. Keep that in mind when you feel you are getting lost in the catacombs of vision, image formation, and numbers!

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Thanks so much for the comment.

Let’s see…

Think of colourimetry as an encoding system. We can encode a “coordinate” using negative values.

Relative to the encoding system, such as the purity available to the BT.709 medium, the negative values are bogus nonsense and mean nothing within that system; it is impossible to express a purity “more pure” than the maximally pure value, or “more emissive” than the maximal emission. Relative to a Standard Observer encoding model however, the coordinate can be “meaningful”.

> How should negative values be handles by tonemappers/display transforms?

It’s a great question and the answer is *no one has a shred of a clue*. The reasons are many. To name a few:
* No one understands how pictures work.
* Negative values indicate stimulus that is “purer” than other values, and how to handle that without breaking neurophysiological mechanics is incredibly complex. We really are in an infancy of understanding. Maybe pre-infancy.

A “clip” of a negative lobe, because it represents *negative stimulus*, ends up *artificially increasing the stimulus* and “deforming” the “intention”. But none of that really matters too much until we get minds thinking about what pictures are, how they work, and what mechanics are being leaned into.

The vast majority of the brain wormed discussion around colourimetry is so utterly ill framed that it amounts to noodleberries humping footballs to collect a bag. This includes books written on the subject of “gamut mapping”, because the basis is so utterly disconnected from neurophysiological mechanics so as to be nothing more than incantations of magic trying to control the ether.

For anyone reading this, skip all the rubbish around colourimetry, and focus on the minds like Eric Schwartz and Stephen Grossberg. That’s where the real work rests before us, and we haven’t even begun to scratch the surface with respect to pictures and their formation.

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