Hi Bun-H,
Nice that it worked for you.
.
Your HDRI Gamma question, I assume based on the Material Editor.
Yes, it looks funny when you think that it is named HDR-Gamma, and then it is grayed out, while having an HDRI loaded.
Well this is not new or recently. The simple way to get control over it back, (and why one shouldn’t - is explained below ;o) is to switch off Linear Workflow and set the use of “Input Color Profile” in images to Disabled.
In this moment it switches back adjustable again.
Ok, this will lead perhaps to options outside of my knowledge or wildest imaginations, given a true light workflow. Let me explain my idea about it.A gamma value is based on the mid gray impression of an image, or the 0.18 value (0-1) or 18% gray. Which we receive as 50%, hence the confusion you might read about in older forum entries all over the place.
The “black” and “white” point are never touched in gamma. Only the mid value, based on the formula, changing values slowly from 0 to new mid to 1. So, again, the 0 stays zero and 1 stays 100% or one. The resulting curve works fine for gamma based images. However this formula continues with values above 1 or 100%, but as a continuation of the direction above middle gray. Which means in the opposite direction, given a comparison to a diagonal, which would represent the linear distribution. Middle values down, values above 1 (or 100%) go up. Nonsense of course and not useful.
Another way of screwing a scene up is to disable Color Profiles. Each an every color profile is untouched as information source, but in the moment an image is based on the color profile, the pixel values itself become changed. As long as the app knows the profile’s specifics, all is fine and the values can come back as far as possible (8bit/channel/integer—might have some losses—naturally).
Typically the gamma coding is in the Color Profile. They are not always the same, as is not the Color Profile by itself, they are many very different profiles based on very different color Spaces (Gamut), all are different compared to others.
Since we have no “white point” in HDRIs, and in integer (what people call) a white point is just the clipping point, but not a natural white point. Paper white for example can be gray or white or clipped, no definition here. So, the only absolute value we have is middle gray (and even there you might hear arguments…).
One might say we have a black point, well not really, as no material on this planet has 100% absorption, hence why we use in Cinematography (if needed) a color chart with a light trap) to come closer to that point. To have an comparison among all takes. etc.etc.etc.
Since this middle gray point is so crucial, any change will distort the information, and should be applied only to an linear image that was accidentally treaded with an (opposite) gamma value. Anything else is beyond me, and I guess it is good that one need to endanger the whole project to “enable” that feature, it should be even more difficult to do if one would let me handle it. :o)
If in doubt, and if any Color Management thoughts leaves one with any uncertainty, just don’t touch it. If you see even a tutorial-instructor doing so, without need nor any specific explanations, run! ;o)
In a nut shell, if one has no idea if the shooter of an HDRI can be trusted—to have a perfectly referenced gray-value: not just a gray card holding close to the camera and have capturing light that isn’t representing the majority of the scene, don’t even use it. Just be careful. All of that only if you like to work closer to a natural light simulation, anything else is just eyeballing or artistic freedom. Especially old radiance (”.hdr”) images have often a lot of weird and limited colors, and often chromatic aberrations! in the image.)
My best wishes
Image: sketch of a gamma formula applied to a curve beyond 1.0
