COLOR GRADING ISSUE ON ADJUSTMENT LAYERS

Ok... I work for/with/teach pro colorists, have for years now. I spend nearly as much time in Resolve daily as in Premiere. So working with log normalization and LUTs and such is something I've spent hours doing and listening in to other top colorists work with.

And the vast amount of information on YouTube on using LUTs for log-lin normalization is garbage. In any proper technically correct workflow. So some basic schooling.

LUT based log to linear space normalization is pretty much old-school at this point. LUTs are called "the dumbest math out there" by colorists, and for good reasons. There actually isn't any math there. It's totally an application of a simple data chart to pixel data. This set of R/G/B triplicate data goes to that set of R/G/B triplicate location.

They do not have any means of adjusting the changes to the image being changed ... so any difference between the scene lighting/contrast/color levels, and the camera settings/lighting/contrast/color levels, can introduce hard clipping of light areas, 'crushing' of black areas, and/or over-saturated areas. These can not be recovered by any means after the LUT is applied.

So any proper, safe use of LUTs for log-lin normalization requires a multi-step process ... first the LUT is applied to the image, then ... in a step that is processed before the LUT itself, the user trims the exposure, contrast, white/black points, and saturation of the clip to fit what the LUT requires to work properly.

In Premiere, that means applying the log->lin LUT in the Creative tab's Look slot, then using Basic tab controls to trim the clip. Or of course, applying TWO instances of Lumetri to a clip, and putting the log->lin LUT in the 2nd instance Basic tab Input slot, and using the first instance, the higher one in the ECP, to do your trim work. 

And that is still doable ... but ... why would you? 

At this point, only if the paying client says "use this transform LUT or go elsewhere" ... perhaps. Colorists avoid log->lin whenever possible now.

The better method mathematically uses algorithms ... actual real-time MATH!!! ... to do the log->lin conversion. It is nearly impossible to get clipped or crushed or oversaturated pixels using the algo's made by any NLE. They are safe and reliable and fast. 

In the 25x. versions and forward, Premiere uses algo's for most log media now. Pretty good ones too. They've been tested by some very high-end colorists, who have no issues with them whatever. And I do mean high end people.

That's turned on in Premiere's new (and pretty awesome) color management, by using  the auto-log detection setting combined with the auto-tonemapping setting.

Is it a different initial "look" to the image than any LUT you've been using? Of course. But then, there isn't any magical "perfect" LUT for any log->lin normlization anyway. ALL log->lin LUTs have both technical and aesthetic choices made in creating them. This is why the camera makers often provide multiple such LUTs per camera. Depending on which look you like with what camera and what scene content.

So for nearly all users, I highly recommend using the PrPro algo's for log->lin normaliztion. 

Then do a testing of Lumetri settings to mod the image for the basic 'look' you like for contrast, tone curve, hue response, sat, and such things. Save for that camera, and simply drag/drop onto the camera's clips in the bin. That's turning it into a "Source effect" which is applied to all bits of the clip anywhere in the project.

And save yourself a ton of time and work. As now, all you need do is trim the clips a bit to match brightness/contrast/sat down the line of the sequence. But moderately to rather small changes should be all you need.

Don't work hard. Work smart.

I think I've made some mistakes while grading. It might be works differently if you add luts into basic correction panel or creative panel.