Where to put LUTs?

[pedzsan]

Various web pages tell me to put LUTs down the path 

/Users/{user}/Library/Application Support/Adobe/Common/LUTs and they talk about two subdirectories: Technical and Creative.  Today on my Mac (macOS 12.4) there is also an Input and an Output subdirectory and I can't find any mention of what they do.

I'm trying to find a convinenet home for LUTs to convert from (e.g.) Canon CLOG 3 to Rec 709.  I was going to put them in Technical but thought I'd ask for some advice first.

[R Neil Haugen · Accepted solution]

Ok ... yea, it's confusing more than it used to be as they've added places to use/reference LUTs.

Technical folder ... these are 'seen' only by the Lumetri panel Basic tab's "Input" LUT dropdown.

Creative folder ... these are seen only by the Lumetri panel Creative tab's "Look" dropdown.

Input folder ... these are seen only by the new Color Management options in the Project panel's clip context menu.

Select a clip, right-click, Modify/Interpret Footage, near the bottom, the Input LUT slot for CM.

Output folder ... this is a question still. I think it's supposed to be seen by the Export page's Effects tab Lumetri Looks/LUT option, but doesn't seem to show there.

Neil

[R Neil Haugen]

Now a bit on recommended LUTs usage ...

All LUTs are built off test media. If your clips perfectly match the exposure, contrast range, lighting, WB, and camera settings used to create the LUT, the LUT should work directly with your clips.

The chances of that are rather slim, as field-shot clips never match studio test lighting setups.

So LUTs will clip highlights with the least "overexposure" compared to the expected signal data. And they will crush blacks with the least undeexposure or wider contrast range than the test media. And this is non-recoverable after the clip. The data's just cut.

In order for LUTs to work, you must "trim" the clip's exposure/contrast/blacks/whites prior to the LUT ... while viewing the clip with the LUT applied and checking the scopes. To do that in Lumetri means using the Creative tab's Look slot for all your tech conversion LUTs.

As then you can use the Basic tab controls to trim exposure, contrast, whites/blacks and sat to best effect while using that LUT. And you do not lose signal data.

This is the way Resolve works: apply a LUT to a node, the LUT is always the last processed item of that node. So if you then make any trims to the clip with color controls in that node, the trims are applied before the LUT is calculated.

I've pushed the Adobe color scientist to re-work the Basic tab to put the Input "Technical conversion" LUTs at the bottom of the tab for proper workflows. He's ... considering it.

Neil

[pedzsan]

Gerald Undone has a long YouTube where he talks about about LUTs but he is using Resolve.  He was also using a nice color chart from DSC Labs during his talk.  I thought "Hey... that would be very educational.  I could get the test chart and piddle like he did with under exposed clips, over exposed clips, etc".  But $$$$$$$$ that chart is $350.  So... that's not gonna happen.  I know that the chart isn't necessary but I think it would have made the experimenation a bit more fun and a bit more precise.

Along the way, he mentioned that LUTs assume perfect exposure and demonstrated what happens if it isn't.  He also pointed to LUTCalc.net where you can create a LUT with various things "customized" such as if the footage is over exposed.

On a different topic.  I don't know how I did it but at least once I managed to get two Lumetri panels on the source clip.  So... you could use the first to adjust the white point, etc and then drop the LUT onto the second one.

Various places have encouraged the use of Resolve -- especially as the final stage.  All of those things are on my "To Be Learned and understood" list -- which grows but never shrinks it seems.

[R Neil Haugen]

Oh, it's easy to add things to the "source" clip data. Either drag/drop an effect such as a Lumetri preset onto a clip in a bin ... or with clips on a timeline, click the left-side "Sourc" tab of the ECP, and then touch the Lumetri controls. The effect will be added to the 'Source' data again.

Source clip effects apply to all instances, of any section of that clip, anywhere in that project. A very handy thing at times.

You could also stack Lumetri effects on a clip in a standard timeline use, simply use the option at the drop-down options at the top of the Lumetri panel to add new instance. If running multiples, it's also wise to name them for what they do to the clip.

So you could use the Basic tab's Input slot to add a tech LUT, if you have a prior instance of Lumetri on the clip. And use the prior instance to "trim" the clip into that LUT on the second instance. I find it easier simply to use the Creative tab's slot, and trim via the Basic tab.

Neil