What does LR / ACR really do when a user changes the Camera Calibration setting?
Here's Adobe's statement (for LR4, but I didn't find a newer one and there's no reason for this to change):
Lightroom uses two camera profiles for every camera model it supports to process raw images. The profiles are produced by photographing a color target under different white-balanced lighting conditions. When you set a white balance, Lightroom uses the profiles for your camera to extrapolate color information. These camera profiles are the same ones developed for Adobe Camera Raw. They are not ICC color profiles.
(from http://help.adobe.com/en_US/lightroom/using/WS939594D8-4279-41b4-B8E9-B06BC919EC7C.html )
As far as I can read into this, the Calibration contains the map that transforms RAW data into what we see on our screens. IF my assertion is right, as long as a Calibration "makes sense" (that is, it's generating a result that "kind of" translates into what once was our perceived image, AKA "reality"), it shouldn't matter which one we use for further development.
EXCEPT it's altering the histogram and I can see - vaguely, as Adobe's histogram is more like a "guesstogram" - changes in color balance, shades, "exposure" or gamma AND I don't like when a program messes up with my images without leaving some kind of trace.
Any other changes made in LR can be read afterwards by looking at the settings. Even in what might be a complex preset by VSCO, for example, one can see the R/G/B color curves changing and the HSL setting changing as well, so one gets the (numeric) feeling of what was done.
Understanding settings enables a user to change what is needed.
So, why do I care? Because (a) Calibration does change color tones in a time consuming way to alter afterwards and (b) "Adobe Standard" is not always the most pleasing option.
Again, if it's indeed a complex mapping, or a color mapping, I believe that choice should be the starting point for further processing, except very few people ever mention it as a starting point. (Adobe does. In this obscure Help page I mentioned. And in a YouTube video that's not "by" Adobe itself. No Julieanne Kost sanctified video on that.)
Do note that it's possible to finish processing an image and just go to Calibration and try different settings "to see how it goes". It's just weird for me.
I'd like to know if there are specific views here as to where in the workflow this should (or should not!) fit, learn if anyone has advice on how Calibration might impact results and, of course, try to learn a bit more about all the complex layers involved in Adobe's ACR / LR / PS.
Tks!
Answer
If you wait until late in the process to change camera profiles, what Adobe is really doing is going back, converting the RAW image using the newly selected profile, and then applying all of the adjustments to the newly created image (using the new profile) that you had made to the older image created from the same RAW file using the previous camera profile.
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