How Hard Is It To Create A Broken LUT?

Following up on the LUT Stress Test

Jason Bowdach’s recent Insight on the LUT Stress Test fascinated me. Test images with computer-generated ramps have always been a favorite tool of mine for helping us visualize the work of Look Up Tables. Combine them with scopes and you have everything you need to know about a LUT. Jason’s reference test images added a whole lot more depth to my toolset.

And in the process – Jason has me asking more questions, and after a few days work I’m still not finding the answers I’m looking for. But after reading and watching his Insight, I decided to start off with answering a simple question.

Using normal color correction tools, how hard is it to ‘break’ a LUT?

Let’s be clear here. I know how to break a LUT in about 3 seconds. Just apply a vignette and the exported LUT becomes worthless. In fact – DaVinci Resolve 15 ignores Nodes that have Power Windows. It also ignores HSL selections when exporting a LUT. (I’m not sure if this is a new behavior in Resolve 15, or not? I know when LUT exports was first introduced in Resolve, if you applied a Vignette you’d get some mighty nasty LUTs. But I can’t reproduce that behavior any more – now that Resolve is much smarter about it).

What I’m asking is: If I get aggressive, can I break a the LUT Stress Test in the manner that some commercial film-emulation LUTs do?

In this Insight, you’ll see my many attempts to break a LUT export out of DaVinci Resolve. What do I have to do to break a LUT? Here’s a hint: I had to get super-aggressive with the film emulation plug-in Film Convert to get any image that you could possibly say *might* induce unwanted artifacts. Personally, I think FilmConvert did a great job, even when I yanked every slider around – and it gives you options to export LUTs in several different cube sizes.

If you add LUTs to DaVinci Resolve then don’t miss the end of this Insight!

While spending many hours creating LUTs and re-importing them into DaVinci Resolve 15 Public Beta, I discovered some key new shortcuts that makes this process super-fast and way less annoying. Jump to 14:35 if you just want to see these new shortcuts in Resolve 15.

Coming Next In This Series

Since I’m having trouble creating my own ‘broken LUTs’ I’ve started looking at 3rd party solutions for evaluating and manipulating LUTs – to help us better understand what’s going on. Can we do anything to clean these LUTs up? I’m not sure what the answer is yet. But that’s what’s coming next in this series. And if you have suggested avenues of exploration for me, please let me know in the comments!

-pi