First, excuse my bad english…
The question you ask seems (in its formulation) simple. In fact it is extremely complex as the number of parameters is important.
I am not going to make here a treatise of colorimetry because one could write a novel, but to summarize the essential points.
Preamble
When you take a photo, you are almost the only one to perceive the “scene” as you see it.
In the same way, the conditions in which you are going to look at them after processing depend on your equipment (monitor, TV, projector, printing…) and your environment (in daylight, in a dark room, etc.).
This also assumes that your camera has the “right” input profiles, and that the shooting parameters are correct.
You immediately realize in this statement that there are parameters that can be described as objective, or cognitive, or scientific and others more subjective related to your culture, your perceptions.
It is relatively easy to talk about the first part for example:
- exposure value and camera settings (aperture, speed, sensitivity…)
- white balance, but it is rare that the same scene refers to a single illuminant, for example there are parts in the shade, others in the sun, or the illuminant is composite, etc.
- input profile: is your camera calibrated? what does the profile do - keep it as close to the colorimetry as possible, or drift voluntarily to customize
These steps, not exhaustive, are not simple and subject to many debates between scientists and users.
The second part is more empirical and uses complex notions called CAM (Color Appearance Model). For example 2 colors that have exactly the same frequency spectrum (first part), may appear different depending on what is around. This way of taking into account a certain form of subjectivity has been modeled since 1997, then in 2002, then in 2016. Today the model used is Cam16. Other approaches exist which are in RT like JzCzHz, but we are leaving this simplified presentation.
Of course there is documentation in RT on each of the points mentioned, but the whole thing with a global and coherent view is difficult to explain and address. Nevertheless I will simplify to the extreme and of course we can exchange afterwards on the points to be clarified (as far as our competences allow it).
I will only address a few points assuming the others are known or more usual.
« White balance » , should we trust the camera, its common sense (sun, shadow …) or use scientific concepts? In the case of images based on daylight (or tungsten) illuminant, I would recommend using “auto” / “temperature correlation”. In many cases the (very) complex algorithm, compares a series of dominant colors of the image to a panel of 200 colors predefined by their spectral data. You get a setting that acts on the temperature and tint with a correlation coefficient. The result is often very good, but of course it will not correct the defects of shooting
The “scene” : corresponds to the shooting conditions put in scientific form:
- shooting temperature ;
- “absolute luminance” which corresponds roughly to the peak luminance of the image (expressed in cd/m2 from 0.01 to 16000 approximately);
- “mean luminance” which translates the average calculated luminance of the image
- “surround” allows you to take into account the environment of the image: dark or black, medium, light. In general, you are the only one who knows…
- and another parameter the chromatic adaptation (Cat16) which will allow to adapt the colorimetry between the image and the reference (often D50).
"Viewing conditions" : with the same types of parameters as “scene”, but of course with different values.
Of course there are many other parameters, but let’s leave it at that.
What to do?
Everything that has been mentioned in this thread is relevant and I thank everyone for their contribution.
Of course you can use these modules separately or together, but an image as we have seen is rarely uniform in exposure, lighting and sometimes we go out of the purity (overexposure, underexposure, HDR images, etc.).
A module in RT (Local adjustments) allows for selective retouching, taking into account color differences, transitions and other parameters.
You will obviously find modules whose function is close to those of the main module (Color and Light, Exposure, Vibrance, Dehaze, wavelet, etc.), but to come back to your title, one that catches my attention is the “Color appearance Cam16 and JCzHz” module. Don’t go for JzCzHz, but for Cam16.
Local adjustments - Color appearance Cam16": I won’t go into detail, but in summary it includes the same items as the (complex) module “Color Apperance and Lighting” (“Advanced” tab).
It has the advantage (if we can use this term) of being simplified with sliders a little more intuitive.
With it, you can take into account the notions of “source”, “viewing conditions”, make the retouching that seems useful to you (lightness, brightness, contrast, saturation, etc.), a first approach to HDR images, and modify by chromatic adaptation and a simple slider “chromatic adaptation/cat16” in “Viewing conditions” which allows you to warm up or cool down part of the image.
Of course this text, already long, is only a summary and a brief overview of the possibilities.
Jacques
