FS7: A million dumb basic questions about LUTs

LennyLevy said:
Also it seems to be taken for granted that Premiere and Resolve handle LUT's differently. Can anyone explain that difference?
Click to expand...

It's not just that Premiere and Resolve handle LUTs differently. It's that they decode video in a few different ways. So you need different LUTs depending on which camera, format, and video software you're using.

In Resolve when the clip attributes data levels is set to "video", Resolve places the display-referenced black point (0% R'G'B') of the decoded video at 0.0 in the RGB working space, and the display-referenced white point (100% R'G'B') of the decoded video at 1.0 in the RGB working space. Set LUTCalc's input range to 100% for this case. Use LUTCalc 3.1.2 or later and set the LUT Type to DaVinci Resolve 12+ auto to ensure that the LUT will be able to access values in the 100-109% range.

In Resolve when the clip attributes data levels is set to "full", Resolve places the display-referenced black point (0% R'G'B') of the decoded video at 0.063 (64/1023) in the RGB working space and the display-referenced white point (100% R'G'B') of the decoded video at 0.92 (940/1023) in the RGB working space. Set LUTCalc's input range to 109% for this case.

If your LUTCalc output is a display color space (e.g. BT.709), the output range should be set to 100%. It's up to you how you want to set Hard Clip for your output. Hard Clip "Both B&W" creates a broadcast-legal signal with no RGB values outside of 0-100%. "Unclipped" can produce values below 0% and above 100% that would normally be clipped by your display, but you could manually manipulate the color values to bring some of those within the 0-100% range if you wanted.

Premiere's decoding largely matches what Resolve does when the clip attributes data levels in Resolve is set to "video", though there are a number of different corner cases that Resolve and Premiere each decode incorrectly. For Sony cameras and S-Log1/2/3, I believe both Resolve and Premiere decode video in the same correct way. So for Premiere, set LUTCalc's input range to 100%, in which case input values above 100% will be clipped. LUTCalc can create a LUT that will access values above 100%, but Lumetri doesn't properly apply the LUT to values in the 100-109% range. So practically speaking with LUTs in Lumetri input values above 100% will be clipped.

Incidentally, Logarist doesn't have that limitation because it doesn't rely on Lumetri for loading LUTs. Logarist LUTs can all access the full range of color values produced by the camera, including values in the 100-109% range, and values below 0% for some cameras too.

Edit: had to check my notes for the behavior of LUTs in Lumetri.
Edit: I just found the LUTCalc bug for setting input scaling in DaVinci Cube LUTs, fixed in v3.1.2.
 
Last edited:
morgan_moore said:
(ACES) You need a monitor which is calibrated to your target deliverable.

My (wooly understanding) is that you grade on a high spec monitor and the data/gamut/gamma is compressed to the deliverable 'width' by the ODT (output display transform) upon export

The whole purpose of ACES (according to my wooly understanding) is to grade once for many deliverables not to grade to the gamut/gamma etc of the deliverable.. giving a huge time saving and look consistency to a production that needs to produce different deliverables (phone, apple trailers, broadcast, cinema, future unknown device)

So you exactly dont grade on a monitor of your target deliverable, although a test would of course be prescient to check the ODT is functioning properly.
Click to expand...

That is not necessarily the case. With ACES you can grade on a P3 projector and then render through a Rec.709 ODT, but I would not advise that if Rec.709 is your "primary deliverable". I would recommend that you grade on a Rec.709 display in that case, using the Rec.709 ODT. If you subsequently manage to sell your film to a distributor, and need a P3 version, you can then take it to a grading suite with a P3 projector and do a trim pass there with the DCI-P3 ODT enabled, which should give you a good start point.

You don't just export through an ODT. You monitor through it as well. You would be surprised how good a start point you can get for an HDR version of a film graded through an SDR ODT, simply by switching to an HDR ODT and using an HDR monitor. You still need a trim pass though, as the HDR ODT may reveal things (or make them too prominent) that you couldn't see before.
 
Just wanted to say this is a great thread guys - thanks Lenny for asking the "dumb" question - and for everyone's input. While I'm digesting some of the info - just wondering now if all NLE's have minor variances in how they "decode" video?
Avid? Vegas ? FCPX? (to my knowledge FCPX is the only one that can "automatically" apply a conversion lut to log footage upon import - though I don't suggest anyone doing it that way)
 
balazer said:
Edit: I just found the LUTCalc bug for setting input scaling in DaVinci Cube LUTs.
Click to expand...

Thanks for the heads up on that - I've traced the mistake and uploaded a correction. The online version has been adjusted (v3.1.2), and once the build has passed the app store, the Mac app version will update with the fix. I'll also upload the Chrome app version then,

Ben
 
markfpv said:
Just wanted to say this is a great thread guys - thanks Lenny for asking the "dumb" question - and for everyone's input. While I'm digesting some of the info - just wondering now if all NLE's have minor variances in how they "decode" video?
Avid? Vegas ? FCPX? (to my knowledge FCPX is the only one that can "automatically" apply a conversion lut to log footage upon import - though I don't suggest anyone doing it that way)
Click to expand...

In answer to your first question, yes, different NLE vary in how they decompress video. And, no, FCPX is not the only NLE that can apply a LUT on import, Avid can do this. Why you'd want to do this though, is another matter.
 
Well I just downloaded logarist and applied to a FS7 clip. Applied the standard sony fs7 lut to an identical clip and the difference is kinda really really better. (yep, I said that)

Always thought sony lut was written specifically for fs7 but I could never get skin to look right. Logarist seems to get that right straight out of the box.
 
Chris Johnston said:
I just downloaded logarist and applied to a FS7 clip... ...Logarist seems to get that right straight out of the box.
Click to expand...

I found the same thing when I did this with GH4 Cine-D and V-LOG L footage, the Logarist system instantly fixed the horrible yellow-greens I always saw with other color systems when shooting grass or tree leaves.

Can't wait until the Logarist system supports GH5 V-LOG L footage.
 
Interesting Thread.

My standard LUT is the arri Alexa LUT that comes with Davinci. I like it more than the Sony standard LUT.

I will give the Logarist option a try.
 
Last edited:
I don't get Star Central's negativity toward Logarist. If you don't like it, then don't use it but don't trash others for using it. I don't think it is imprecise at all.

Correct me if I'm wrong but Logarist is not "an exposure tool" or "imprecise," it is color space that you can work in using the existing controls in your NLE. How is that imprecise? Are you saying the color space itself is imprecise?

I am not defining color correction any way I want.

Primary grading refers to grading that affects the entire image.
Secondary grading refers to grading just a part of the image.
That's not something I just made up.

If I've learned anything on this forum, it is to test things out for yourself and at some point, you've got to trust that. I can grade by hand, try different color spaces, or use LUTs. I will try different ways to see what works best. I can use Resolve, Premeire, Film Convert, Vision Color, Logarist, whatever. All I care about is if it looks the way intended.
 
TheDingo said:
I found the same thing when I did this with GH4 Cine-D and V-LOG L footage, the Logarist system instantly fixed the horrible yellow-greens I always saw with other color systems when shooting grass or tree leaves.

Can't wait until the Logarist system supports GH5 V-LOG L footage.
Click to expand...

I'm already using Logarist for my GH5 V-Log L footage, and it works great - including the PQ (HDR10) output LUTs from @Balazer.

Piotr
 
Report from the guy who started this thread:

I ended up testing a bunch of LUT's made in LUTcalc both with Slog3 shot on FS7 usually around 800-1250 ISO and also stuff shot on A7Sii with SLOg2 and the ISO on camera set to 1600 but overexposing another 1-2 stops to keep noise floor clean.

I've been having good luck with LUT's made Data in and Legal OUT (also turned off all clipping). Generally it works well when the ISO's I set in LUTCalc are a little higher than what I thought I was exposing for. The LUT's of course are just starting points and images still need tweaking re Saturation & Levels of course but they generally look pretty good and the color is usually spot on. ( I get carried away with secondaries also, but that's another story.)

I've had mixed results with Logarist and especially with the overexposed SLog2 A7Sii files. Here I found it had a tendency to clip highlights as was noted elsewhere. However I can't say I've worked with it carefully so don't want to be too critical.

One thing I've noticed in Lumetri/PP is that there isn't a good tool for bringing back the extreme highlights. I used to do these easily in FCP7 with a 3rd party highlight/shadow filter that was terrific. Apparently there was also something like that in premiere but it strobes on output and has never been replaced. Too bad. Especially when using Slog 2 way overexposed on the A7Sii there is clearly material left in the highlights that I can see in the log view but I can't seem to hold it once I add a LUT no matter what I do in Lumetri. My guess is this would be easy in Resolve.

I haven't had time to dig into Resolve yet but I can see right away that it will probably be a lot quicker and more intuitive than Lumetri just because you can clearly see and change what filters you've applied in what order . In Lumetri its just a lot easier to lose track of what you have or haven't done. Plus in Resolve it would be easier to make changes in more targeted area and levels.
 
I suggest using Premiere's RGB Curves when you have highlights you want to bring down. Apply the curves before the LUTCalc LUT or Logarist output LUT. RGB Curves does a better job than the curves built into Lumetri, I've found.

BTW, what ouput gamma and gamut are you selecting in LUTCalc?
 
Last edited:
Thanks i'll try that Balazer.

Target Gamma has been either Varicam 709 for more punch or 709A.
Target Gamut has been 709A

I haven't experimented with target Gamut at all. Feels like a black hole to me.
 
LennyLevy said:
I haven't had time to dig into Resolve yet but I can see right away that it will probably be a lot quicker and more intuitive than Lumetri just because you can clearly see and change what filters you've applied in what order . In Lumetri its just a lot easier to lose track of what you have or haven't done. Plus in Resolve it would be easier to make changes in more targeted area and levels.
Click to expand...

Finally you are discovering the answer to your own question. Stop farting around with Premiere and just get going with Resolve right now, because sooner or later you are headed there anyway. Do you know any professional colorists who grade in Premiere, Avid, or FCP? I hope not. If you're going to shoot S-LOG or RAW you need to grade in Resolve, Baselight, or some other dedicated grading application.

I'm not saying that experimentation and finding out things for yourself is a waste of time, but I know you'd already be well on your way to figuring out Resolve if you had just gone there in the first place instead of spinning your wheels on other workflows. Here's the little secret about Resolve: It actually makes grading easier, not harder, once you see how simple it really is.
 
Doug, you are so quick to judge.

I had to start with Premiere because the editors of my projects are using Premiere and part of what I've been doing is getting them color corrected files & window dubs to work with that are integrated into their flow.
 
So quick to judge? I'm offering you support and encouragement that you are headed in the right direction. Never mind, I will stay out of it.
 
Doug

We have to be across both methods.

1) be able to tell clients how to do a basic de-log and ISO change so that our clients get to the point that they saw on the location monitor

2) make the best of our footage using the best tool

If we can't nail (1) then clients get driven away from log and we are forced to shoot baked and clamp reduce the potential of our cameras in camera - this procludes 2 ever happening

2 is clearly the way to go in the long term :)
 
Don't take me too seriously Doug, and definitely don't take that to mean you should bud out. I've been reading you for years , occasionally arguing with you and more than once been incredibly pissed off at your manner, but that doesn't mean I don't appreciate your input a great deal and haven't learned a great deal from you as well. Keep it coming, i'm a big boy! :)
 
You must log in or register to reply here.
Back
Top