Output Transform Tone Scale

[Troy_James_Sobotka (troy_s)]

Sean, this whole post is fantastic. Thank you.

These two quotations from the post are extremely useful, and build on top of what @Alexander_Forsythe and a few others have been fleshing out, with respect to “tonality”:

@SeanCooper

He defines the problem space as “…the extent to which it is possible by the photographic process to produce a pictorial representation of an object which will, when viewed, excite in the mind of the observer the same subjective impression as that produced by the image formed on the the retina when the object its self is observed…”. He then goes on to say “The proper reproduction of brightness and brightness differences…is of preeminent importance…”.

@SeanCooper

Brightness does have a definition in the color science community, to quote Fairchild “…visual sensation according to which an area appears to emit more or less light”.

It strikes me that perhaps Fairchild’s definition would need extending for usage with imagery output contexts? Specifically, it would seem that we would need to define “brightness” relative to the light transport data in the buffer in question?

@SeanCooper

We would do well to define “Film” in the same rigour as “Tone”, because I don’t believe the objective here is to emulate a single batch of a single brand of photo-chemical film processed on a certain day.

Could not agree more. Perhaps chasing “Film” altogether, and instead interrogate the fundamentals that worked to deliver this “brightness” facet above, would be potentially more forward looking given the radically different nature of constant chromaticity emissive / reflective display devices?

Any such algorithm would need to be based on such a mechanic. If we examine the existing chosen mechanics historically:

Question #1: Is there a useful colour science metric here that we could use as an entry point to evaluate “brightness” relative to the light data present in the working space?

Further along, assuming we can identify a single entry point to trial, we can retroactively test the fitness of existing approaches to see if they pass this metric:

Question #2: Do per channel mechanics facilitate a “…visual sensation according to which an area appears to emit more or less light” according to this metric?

Question #3: Do the “hue preserving” power norms facilitate a “…visual sensation according to which an area appears to emit more or less light” according to this metric?

Question #4: Does any emission-centric mechanics facilitate a “…visual sensation according to which an area appears to emit more or less light” according to this metric?

Thanks again for the terrific quotations and thoughts. I am very curious if anyone has any suggestions on at least a starting point metric we could collectively use to address Question #1. There will likely be faults and problems, but we would at least need to start somewhere…