Are LUTs and "Creative Looks" the same thing?

[stevens70907226]

I bought and just started using a Z7, it's my first time using LUTs. Watching several video tutorials I saw people control the amount of the LUT they applied to their image. I tried applying the LUT in both LUT (under Basic Corrections) and Looks (under Creative) and only under Looks can I affect the amount the LUT is applied. 

1) Is there a way to control the amount of LUT applied to a clip in the Basic Corrections tab?

2) Is a Look the same thing as LUT (if so, then I can just control how much is applied there). 

Thank you,

[Mike Dziennik · Accepted solution]

You can add custom LUTs from the top of the 'Look' menu in the creative tab if you need this control.

The difference is the order of operations - LUTs/Looks applied in the creative tab are applied after the basic correction controls. These are generally for 'creative' looks.

LUTs applied in the Basic correction tab are applied before Basic Corrections and are generally for 'technical LUTs' which are used to convert one colour-space to another.

[R Neil Haugen · Accepted solution]

I teach, work, and learn from/with a lot of colorists daily. And of course LUTs are heavily discussed. Most colorists feel the most important thing anyone should know about LUTs ... is they are purely and simply the dumbest math out there.

They are built as a matrix of data points. The input data of any particular number set, let's say RGB numbers, 25-47-14, gets output to another number. Let's say this LUT matrix outputs that number point set to 23-50-20.

And the LUT causes the app to do this sort of thing all through the incoming image data, depending on how the matrix is set. The matrix can be fairly simple or of course fairly complex. But there is no way to add thoughtful action to them.

That capability is both very useful ... and even more dangerous to your pixels. Most pro colorists have rather intricate LUT stressing tests they'll apply before using a LUT of most any origin. Just because some LUTs can do very strange things with certain clips that you probably don't want to happen.

For us 'general' users, one of the most important things is to understand LUTs are absolutely "dumb" ... they are made typically under "ideal" circumstances, or at least a particular circumstance, of exposure/white balance/contrast to the lighting and camera settings. When used on any clip not lit/exposed/camera-settings identical, they may well clip highlights to whites, crush blacks, and either over or under saturate the color.

This is why when colorists use LUTs, they never ever put them in some place like the Basic Tab's Input LUT slot ... not even for technical tranform LUTs ... because that is before the user has any controls to 'trim' the clip into the LUT. I've argued about that placement with the Pr developers and color scientists, who actually the last conversation I had were willing to talk about moving the Basic Tab's input LUT slot to the bottom of that tab.

Because then 'we' users could apply a LUT, and 'trim' the clip's tonal/color settings in the Basic tab to fit within the requirements of that LUT for proper operation.

So ... I always apply any LUT in the Creative tab's drop-down, so I can use the Basic tab to best fit the clip to the LUT. As an example, I just worked with another user who was having clipped highlights with two different log-conversion LUTs. Definitely bopth are "technical" LUT.s And it turned out that which tab he used the LUT in was the problem.

Because when I tested the affected clip and LUT, with the LUT applied in the Creative tab slot, yes on initial application the highlights/whites were pushed way up and clipped. Just as the user was having happen on their machine.

But because I applied the LUT in the Creative tab, I could easily go to the Basic tab and back the Exposure control down a bit, which brought the highlights/whites down low enough that all detail appeared, there was no clipping of highlights, it was a perfect image. With all the conversion qualities of that special LUT in full effect.

Now ... as to what's the difference between a "Look" and a LUT?

Well, a ".Look" ... a "dot-look" ... note the period, or dot before the L? ... techically is a particular form of .cube LUT. And that format of cube LUT works mostly in Premiere Pro, you might not get it to work in another application. "Dot-Look" files I think came out of the sadly departed SpeedGrade color grading app Adobe used to produce.

And they are still an option in the Lumetri workspace as one of two LUT formats they allow us to use. They do not work in the Basic tab slot, only in the Creative tab slot. I've never seen a .Look LUT be accepted in Resolve though, for instance, even though Resolve does take a fairly wide array of LUT types.

Outside of Adobe apps, a lot of people talk about "look" LUTs versus tech LUTs, and for that discussion, Mike's comments are spot on. A "look" type LUT is designed to essentially 'grade' the image for a particular feel.

A tech LUT is designed to do a specific mathematical transform of the clip, say from one color space to another. Or from a Log or RAW state to a display state, say Rec.709 or Rec2100/PQ. Transform from say SLog-2 into ArriWideGamut ... that sort of thing.

Neil

[R Neil Haugen]

Adendum: NEVER EVER EVER add LUTs of any form/format into the program/package files locations for Premiere Pro, MediaEncoder, or AfterEffects! Not EVER.

Use the following charts ... and for some reason they don't make the final folders in these locations, so you need to make the Technical and Creative folders. I've seen a couple users even had to make the folder above those.

Why? The LUTs in the program/package folders for each app are accessed by relative position in the folder, not by name! So if you add anything there, it changes the order ... and therefore, which LUT is applied. And even worse, if you add a LUT in the Premiere pro program files, but not in MediaEncoder ... and queue the export to MediaEncoder ... you'll get the relative number down the list LUT applied. So if your LUT was the seventh in the Pr folder, it will apply the seventh LUT in the Me folder.

Not what you want to happen.

Neil

 

[Mike Dziennik]

Agreed. Applying technical LUTs before trimming rarely works; except when that LUT has been used and monitored on set to determine the exposure: eg. film/drama sets.

In the past, I've done most of my grading in Resolve: even there, I would apply LUTs as a downstream node, after an initial 'trim' node.

99.99% of the time (in all other non-film/drama scenario's) you will need to trim before feeding into the LUT - both 'technical' and/or 'creative'.

[R Neil Haugen]

In Resolve, whenever you add a LUT to a node, then within that node use any other controls whether wheels, printer lights, curves, whatever ... all 'regular' controls in that node will be processed before any LUT applied in that node.

It doesn't matter which order the actions are applied, the LUT is processed last even if added first.

That's one behavior I got the Adobe DVA chief color scientist to check out. And of course, he confirmed that that is what was happening. And further, I gave him some papers by A, V, Hurkman and others on proper trimming for tech LUTs. A couple of the MixingLight programs on using LUTs for both transforms and "creative' purposes that also trimmed clips through the LUT.

He is considering changing the behavior, acknowledging it has solid application and use reasoning. That's all I know about it at the moment. That was a major statement by a staffer, but of course, an Adobe development team "considering" something doth not unfortunately imply imminently ... or ever ... actually changing anything.

But I do hope they do move the Basic tab's Input slot to the bottom of the tab and that tab's processing order.

One thing that has me ... curious ... about the 2022 build series. For several clips that have 'clipped whites' that users have sent me, I've been able to use the Basic Tab Exposure slider to pull down the whites such that clearly, there was no clipping. This was with Premiere having clearly applied a 'default' applied Log transform in the 2022 version, and HLG clips.

That is not behavior I would have expected. As any corrections after a transform/tech LUT that induces clipping cannot bring back clipped detail ... and I wonder ... are they applying the new default LOG transforms after the basic tab? I forgot to check if say the Wheels would have the same result. They may or may not. I'll have to remember to try that.

Neil

[Mike Dziennik]

In Resolve, whenever you add a LUT to a node, then within that node use any other controls whether wheels, printer lights, curves, whatever ... all 'regular' controls in that node will be processed before any LUT applied in that node.

Yes, you've jogged my memory. I had a colleague who did it that way, trim and LUT in same node. I started using seperate nodes before I realised (when he showed me) you could do it in one...I kept using seperate ones just as a personal preference thereafter.

It highlights the issue, that even in a node based pipeline, the order of operations isn't always 'black and white' (excuse the pun). Without a node tree (as in our case with Premiere) the order of operations is even more obscured. Would be interested to hear if the wheels can recover detail too.

[R Neil Haugen]

I just checked ... Pr defaults to interpreting some footage as HLG, such as with a Sony S-log3 MXF clip. When I changed the scopes color space to HGL and set the scope scale to HDR, it showed it was taking the whites to somewhere between 4,000 to 6,000 nits.

WAY blown out on a Rec.709 timeline. But ... interesting bit of data here ... I could use any major tonal control in any tab of Lumetri to bring back data unclipped. The Lumetri effect is clearly being applied before the CM for the clip.

I could use the Exposure slider in the Lumetri Basic tab (the widest-ranged control in Lumetri) to pull that down so that a bit of Highlights and Shadow changes brought the file into decent view on a Rec.709 timeline. I could also use the RGB Curves tab.

However, the Color Wheels Whites tonal control simply doesn't have the range to pull the whites clear back to within Rec.709. It did a lot, but again ... doesn't have the total "pull" of the Basic Tab Exposure slider.

But for most work, it's far easier to Modify/Interpret Footage/Override to Rec.709. Then just add a bit of Contrast and other things to normalize the clip.

Further interesting data: normally, changing property on a clip in the bin only applies the change to new use of that clip on a sequence. But changing the CM settings via Modify/Interpret clearly changes the clip anywhere it's in use. Which ... is sort of good, but may not be what we always want ...

Neil

[stevens70907226]

Thank you so much for the detailed explanation. 🙂

I see a lot of YouTube creators who have created LUTs for their channels (my favorite example of this being BeckiAndChris). If ever I did want to create a LUT for the overall color, do you have any suggestions on where I can begin to learn how to do it? 

[R Neil Haugen]

First, the color management practices, settings and default behaviors in Pr 2022 are completely changed ... I wrote a FAQ for this forum that I've updated already four times for 'new' information. Check this out to understand what's going on, and how to use Log media, HLG/PQ clips, and work in either Rec.709 or HLG/PQ and export successfully.

Any color work in Pr2022 can be problematic if you don't understand all the changes.

FAQ: Premiere Pro 2022 Color Management for Log/RAW Media

As to creating LUTs ... there are multiple reasons for creating and using LUTs. First, you need to know where you want to get to, and that you can get 'there' from any incidental 'here' with a LUT.

For example, a manufacturer of a camera makes a LUT for converting a log format captured by that camera into Rec.709. To set this up, they create a "perfect" situation: controlled lighting color, amount, and contrast with the camera set precisely in the middle of the settings needed to nail that exposure.

Then they take that media, and apply color correction settings in some app to 'fill' the Rec.709 image on a calibrated Rec.709 system and monitor. It works beautifully.

But the user has a clip that is slightly lower in exposure than the manufacturer's ideal setup. Applies the LUT, and wow, some blacks are crushed! Or the obverse ... very slightly higher exposed compared to the manufacturer's setup, and some whites are totally clipped, gone!

What happened?

That LUT was 'built' for the Ideal Exposed/Exposure Clip. Real media rarely is that perfect. So users need to apply such a LUT but adjust the clip tonal/saturation properties before the LUT. It's called trimming into the LUT. So you lift the values a bit to keep from crushed blacks, or lower the whites a bit to avoid clipped whites.

Other LUTs are "simple transforms" say from one color space or gamut to another. And some LUTs are totally for "look" of the final image.

They can all have some of the same problems. You need to know that when making them, and ... when applying them.

Past that, colorists do stress-tests on LUTs before using them. Which means putting them on test media that's out towards the edge of things, and watching the scopes to see if they "break" the clip. Get artifacting or odd behavior either visually or in the scopes. This sort of thing takes some study to really understand and start applying.

Second, you need to simply test any LUTs you create on a range of media. Unless you are creating them for say one specific media type and use. As in ... take John's RED Dragon clips and transform to Rec.709. Being as John always leaves his camera settings pretty much the same.

Whether it's a tech LUT for converting log to Rec.709, a transform LUT from one color space to another, a "look" LUT for a show or project, you need to test on any possible media you intend to work with that LUT. A range of exposures, color balances, skin tones, contrast ... and make decisions based on using that LUT over several situations.

Neil

[stevens70907226]

Thank you again. I read the post you linked to. I would not have known any of that without your pointing it out. 

Do you have any recommendations on books, articles, or videos to learn about the technical aspects of gammas, LUTs, and color grading? Shooting film I understood. Doing photography on a DSLR I'm comfortable with. Creating and editing video on mirrorless Nikon, I feel I'm flying blind. 

I have an appointment on Thursday for the RAW upgrade on my Z7. Do you have any suggestions or know of any books to help prepare me for working with RAW video footage? 

[R Neil Haugen]

Anything by Alexis Van Hurkman is golden. The two I'd most recommend are the Color Correction Handbook and the Color Correction Look Book.

You really have to know what the color controls do, how to read the clips to know what to do, and how to get a predictable output before you can start creating "Looks". And the first of these two gives a very good basic look at color correction. The second takes that basis and applies it to common scenarios that the color artist will face.

Steve Hullfish had a couple books out that I got years back that were also quite useful.

Neil

[stevens70907226]

I picked up a Kindle version of the Color Correction Handbook this weekend. I'm mid chapter four now. Thank you for the recomendation, I wouldn't have found the book by myself. 🙂