LUTs and Lumetric colour

Report · Jan 30, 2023

Hi folks,

I'd like to get three things straight in my head please:

1 - Is adding a LUT exactly the same as adding lumetri colour preset?

2 - Adding a LUT is the same as adjusting the controls within Lumetri colour?

3 - Adding a LUT does nothing 'magical' to the underlying data of the clip. It just changes the colour and brightness settings as per any other Lumetri change

Thanks,

Jon

Report · Jan 30, 2023

read this...might help

WHAT IS A 3D LUT? – Brompton Technology

Report · Jan 30, 2023

A LUT is a look-up-table. A very simple concept, really. But using them can be amazingly complex and problematic.

In simplest form, you have a basic replacement chart. When the table specifies so, input value S becomes output value Q, and R becomes Z.

That's all they are, essentially. The link shown above gets into 3-D LUTs, where there are (also spelled out) extended options for X becomes Z.

They can be useful, and they can also be damaging. I work for/with/teach pro colorists, who call LUTs "the dumbest math out there" for a reason.

All LUTs are built with certain .. .expectations? ... as they are built for X media under Y condition ... even if you're not thinking about it when you make one. As that LUT will work as you expect but only when you feed it a clip like the one that was used to build it.

Same white balance, exposure, contrast settings in-camera and contrast of the scene ... all of that.

LUTs also need to be constructed ... and used ... for specific things. Which can be to change media from one color space to a different 'look' within that color space, or to change from one dynamic range or color space to another. The latter ... is very tricky, and any LUT for that needs a lot of testing to make sure it works adequately.

And color space and dynamic range conversion LUTs can not be used in Lumetri!

A lut creation app like LUTCalc (free, web-based) or Lattice can be set to build shoulders & toes with a long enough roll-off that you shouldn't get "clipped" (cut-off) highlights or "crushed" (cut-off) shadows. And can also be set to handle specific color space conversions. Which again, you should then test.

LUTs created within Lumetri

The LUTs created by the Lumetri effect are only able to do "look" changes.You can not do color space or dynamic range conversions within Lumetri at this time.

So things like the settings you've made in the Basic, Curves, and Color Wheels tabs can be 'cooked' into a LUT and applied to other clips quickly via the LUT/Look slots of Lumetri's Basic and Creative tabs.

LUTs from other sources

You can use LUTs from other sources, as long as they are one of the .cube type LUTs that the Adobe apps are built to use. Some "shaper LUTs" such as several of the ones that are included with Resolve do not at this time work within Premiere.

You cannot use LUTs within Lumetri as noted above to perform dynamic range or color space conversions. Any such LUT must be applied in the Color Management Controls process ... right-click a clip in the project panel, Modify/Intepret Footage, at the bottom in the CM controls ... Input LUT slot.

Storing your and acquired LUTs on your computer for use in Adobe video apps

There are a couple locations they have setup for all three Adobe video apps to check on launch for user-added LUTs. And you must use those, never ever ever add LUTs into the Program or Package folders with the installed LUTs!

If you look up their Online Help manual/documentation, they have a section on LUTs that has a chart with the two locations specified both for Macs and PCs.

My preference is the Progtram {Package on Mac) Files folder, Adobe/Common/LUTs ... note, this is the Adobe/COMMON folder and NOT Adobe/Premiere Pro folder!

Inside Adobe/Common/LUTs, there should be folders for Creative (Creative tab), Input (CM Input LUTs) and Technical (Basic tab). If there aren't, create them.

And store your LUTs there. In folders where you will use them within Lumetri.

My recommended use of LUTs within Lumetri

As LUTs are built for certain media, given a certain exposure/WB/contrast/saturation between camera and scene, there can be problems applying to other clips.

Such as if the exposure of the new clip is a little bit brighter, you may "hard clip" the highlights cutting off detail, or "crush" the shadows to black, again cutting off detail. You cannot get that detail back after the LUT is applied in the processing!

So it is at times necessary to "trim" the clip prior to the LUT so that the LUT works as expected. And this is easy to do if you apply the LUT in the Creative tab "Look" slot.

As then you apply the LUT in the Creative tab, and use the controls of the Basic tab (which are applied pre-Creative tab) to adjust the exposure, contrast, shadow, highlight, saturation, and black point to best advantage for fitting that clip into that LUT.

The difference between LUTs and Presets

A LUT is a baked-in set of image parameters. You can't change them.

A Preset is the actual effect ... in this case, the Lumetri effect ... saved with the settings as they were when you created the Preset, and named by you for what it does (hopefully ... ).

Lumetri presets are quite useful ... for example, you can drag/drop them onto selected clips in a bin, and therefore apply that preset on all of those clips in every place any bit of any clip is used in the project.

Or apply only to selected clip sections on a timeline panel, where they only apply to those bits as used on that sequence, but on no other seuquence in the project.

Presets can of course include LUTs in them too ... which is a great tool for applying adjustable changes as a "bulk" operation, saving you TONS of time.

And per clip, you can then go in and do the minor adjustments to make all the clips fit together.

Presets are a powerful time saving tool that also makes fitting your clips together visually a much easier, faster task.

Neil

Report · Jan 30, 2023

1 - Is adding a LUT exactly the same as adding lumetri colour preset?

2 - Adding a LUT is the same as adjusting the controls within Lumetri colour?

3 - Adding a LUT does nothing 'magical' to the underlying data of the clip. It just changes the colour and brightness settings as per any other Lumetri change

1- no
2- no
3- yes if it's color space in general ( like log to rec 709 )

see the definitions of luts and specifically the categories....

============ from link I provided.
Technical LUTs:

Display calibration: LUTs are used when calibrating monitors or other display devices for colour critical work such as editing or grading
Colour space conversion: LUTs that convert from different colour spaces, e.g. converting Rec 2020 to Rec 709
Camera LUTs: LUTs that are often created by the camera manufacturer to convert camera logarithmic formats that digital cinema cameras typically capture footage in (which look very washed out to the eye) into Rec 709 or Rec 2020
Creative LUTs:

LUTs can also be used creatively: for colour enhancement, creating monochrome or sepia effects, boosting shadows and highlights, or replicating the look of a particular film emulsion – the possibilities are endless.

LUTs can also be both creative and technical, such as those created by DIT (digital imaging technicians) and stored into ‘LUT boxes’ connected to on-set monitors that combine a camera LUT with a creative LUT. This is helpful for giving some idea to the film crew on-set of what the camera is capturing might end up looking like when it has been graded in post-production.
=============

there is a difference between resolve and PPRO with regard to how grading is handled. Nodes are used in Resolve and as you add nodes to make changes in grading those nodes only effect the clip they are applied to and don't change the lut or get cooked into a lut that was applied to the base color space for your project. it's just a next 'step' to adjust that clip. if you make a 'shared node' than that is about as close as it gets to lumetri preset. if you apply the shared node to all clips it does the same thing. but then if you want to change a clip with a shared node you have to add another node ( instead of changing the shared node which would effect ALL clips sharing it ) and make secondary grade adjustments to that clip.

Report · Jan 30, 2023

Resolve is a very differently structured app than Premiere. So much so that in my experience, discussing Resolve around newer people just trying to work in Premiere, is often more confusing than helpful. (And I do teach pro colorists based in Resolve, full disclosure ... )

So if you're just getting started in video production, and working for now in Premiere, you might choose to skip any tech discussions on the differences between them.

Or you might ... like me ... be a glutton for punishment and keep going.

- There's a major limitation within Premiere to be aware of: while you can apply a "normalization" LUT to set the look of a log-encoded clip (that grayish look) to full tonal/color contrast in Premiere, you cannot do color space or dyanamic range transforms on a timeline in Premiere.

Dynamic range and color space conversions in Premiere must be done in the Modify/Interpret Footage CM controls in the Project panel at this time.

In Resolve, you can do as much dynamic range/color space conversions in a 'grade' as you wish. But you must know how they all 'fit' within the chosen working color space.

- "Regular" nodes in Resolve function very much like unto stacking layers of Lumetri effects in Premiere. Except for when it isn't of course. Which gets very technical very fast. If you're new to color correction, this ... is a freaking huge rabbit hole.

- Among other changes, you can copy a Resolve 'node', think Premiere Lumetri tab or "layer", and paste only that node on another clip. It would be like being able to select a tab of Lumetri and copy only that tab to other clips. Which of course many of us Premiere users have asked for, for the entire time since we lost Adobe's SpeedGrade app.

- When you apply a LUT in a node in Resolve, that is always the last thing processed of that node. So you can either apply a LUT in one node, and "trim" the clip to fit that LUT in a previous node ... or actually, apply color correction to the node with the LUT to trim in the same node.

As within Resolve, all color/tonal control changes applied to a clip in a node are processed prior to any LUT applied in that node. Some colorists trim their LUTs in the same node they apply them, some in the node prior, either works.

And Resolve works with a wider array of LUT types than Premiere can, because well ... Resolve started and still exists primarily as one of the top two video grading apps.

Neil

Report · Jan 30, 2023

getting back to basics I'm interested Neil how you would answer the question...

========

1 - Is adding a LUT exactly the same as adding lumetri colour preset?

2 - Adding a LUT is the same as adjusting the controls within Lumetri colour?

3 - Adding a LUT does nothing 'magical' to the underlying data of the clip. It just changes the colour and brightness settings as per any other Lumetri change

1- no
2- no
3- yes if it's color space in general ( like log to rec 709 )

=============

if we keep it simple how would you answer the questions 1-3 ??

I'm just curious.... for the posters sake.

Report · Jan 30, 2023

1) No.

Not even close. (Although within Premiere you need to work in a Lumetri instance to add a LUT, except for the CM controls in Interpret Footage.)

2) No.

If you are working with controls in Lumetri, you can change them at will. A LUT is a baked-in instruction set. Which you cannot change after the creation of it.

3) Invalid question. Because there isn't any magic here at all.

Color in video post is all mathematics. Purely, only, ever. There are various ways to handle the calculations, from very 'active' mathematical transforms and tonemapping algorithms to the more typically static nature of LUTs.

LUTs are a rather limited form of a typically very static math. An end result calculation. Which is very useful for certain tasks. And can be very destructive if not used with caution and care.

Whether the task is "normalization" of log-encoded media to the working space, no matter the chosen working space ... a "show Look" ... or a dynamic range or color space conversion ... LUTs have strict limitations. They are one potential solution to the need of the user.

However, they are the easiest for users to create and invoke. Working at creating full algorithmic tonemapping or suchlike ... well, that involves very heavy work, perhaps in creating a DCTL in Resolve or a similar item. And is something that experts struggle to learn and to master.

Among other limitations on LUTs, one which both surprises many people at first and is of course incredibly frustrating ... you can't add into a LUT the changes made by most secondary "qualifications". Such as setting a key to find the blue pixels of a certain brightness, hue, and saturation ... and changing those to red. Doesn't work in a LUT.

BUT ... if you save a Preset of Lumetri with that qualification key set, well ... that will work anytime it's used.

Ergo ... LUTs are very useful but limited in the use and effects.

Presets (which can include LUTs of course) do not have those limitations. And allow the user to tailor the changes but from that starting ... preset of controls.

Neil

Report · Jan 30, 2023

well, I hope the poster doesn't just give up to learn some basic stuff as well as the more complicated stuff. first of all there is no such thing as an invalid question.

let's go to the beginning of the process of making movies and distribution.

a) shot real movie stuff on sound stages or location using pro cameras with or without luts from the camera to the SDI output of camera to monitors on set to let people SEE what the final product will be after post ( grading ). Sometimes called DIT.

there is hardware to do that in the line ( output from camera to monitors) where lut can be applied without it coming from the camera ( no lut from camera , but added before monitor ).

If someone never experienced this process of shooting real movies on real sets to make a movie they will have no clue what this involves.

That's normal and understandable.

But the process is basically this....

a) preproduction

b) principal photography

c) dailies and post

d) final delivery

the editor does not make the movie... they put the puzzle pieces together and work with producer to get the product for delivery. If they can't do it they get fired right away and someone else gets hired. the editor does not wag the dog.... the dog wags the tail ....

now that the poster is totally baffled by a lot of mud and misinformation about this subject it is unlikely they will ever come back to this thread. But it is important to note that this process is indeed a professional and long standing series of factory-like teamwork with the main goal of making a really nice product for distribution ( to make money cause it costs a ton of money to even START a pro movie process.... it's huge business... script, contracts, actors, locations, and yes, monitors on set to see what you want to have for distribution ( usually rec 709 which in post can be varied for different environments ( projection, HDR, etc. )...but to view it on set it is usually just rec 709 no matter what the main signal is coming out of the camera ( using lut boxes, etc. ).

there is no question that is invalid and now the poster will have to deal with what to do next with this knowledge.... maybe how to shoot, what codec to shoot, what color space to edit in, and so forth. Unfortunately the poster would have to supply some info about specific desires and equipment available to do all this.... and usually in this forum it is an iphone or gopro and youtube distribution... so it's probably moot to continue this thread.

Report · Jan 31, 2023

We came into this thread with vastly different expectations.

I didn't assume anything about the OPs background, or what types of jobs or tasks they are working on. Because although the original questions may seem to indicate a fairly new person at this task, just having been to a SMPTE sponsored event/class ... and dealing there with the editorial staffers for one of the largest companies in the world ... it's clear some very experienced editors can have the same questions.

So I answered the OP of this thread both fairly simply and with some detail. People can take what they understand. And I've plenty experience to know that many will come back for more information if it's of use to them.

Your comments about "the process" are valid ... if and only if ... the editor is working in the siloed, upper-end production setup you list in your steps. And everything else you write is based on that assumption.

Is that assumption a possible one? Sure! That is a process used by some professional workflows.

Is it likely? Well ... maybe, maybe not. Of the several million daily users of Premiere Pro, I would say ... that process is reallistically the smaller side of things. I wouldn't assume that as the most common process.

First, many people that do editing are also involved in the shooting within their operation. That includes a lot of the small, local shops and even some of the video production teams at massive corporations.

Second ... many editing jobs these days involve as much or more "acquired" footage, some stock, some basic contract work, and some a "hybrid". Where the company knows they'll need X type of media, so they hire someone to shoot essentially stock of their company but to their needs. Yes, the media was shot by a crew under contract. But no, the editor working with that media, six months or a year down the road, will never even know who they were nor have any way of being part of the process.

The reality is ... there isn't any clear assumption to make about how "professional" editors work these days.

Neil

Report · Jan 31, 2023

good points, neil, and appreciated, re: venues and workflow. documentaries are often like what you focus on... or industrials, etc. shoot from the hip and after the fact try to get it edited and distributed ( no dailies, no rush, no giant production ). sorta... some docs can be funded and organized with a fixed end product and distribution already in place with editors on board ( like natl geographic etc. ).

anyway there is also a plain fact of life among people in general ( no matter the slot they have worked in .... editors, directors, producers, actors, etc.... )

everyone is capable of having different opions and it's nice to keep that door open.

Report · Jan 31, 2023

Right!

The most fascinating thing for me is to go to something like NAB and listen to others in aisle-way discussion talk about their work and working processes. I wouldn't have believed how varied those are.

Quite literally, no one does everything ... or even most things ... the way anyone else does.

And my assumption has always been that I'm a rather slow and low-skilled "editor" if you're talking about basic cutting a sequence, getting a bit of 'polish' in color/audio, some graphics, and out the door. Compared to those who do those things hours a day more than I.

But actually, there are many of the production items that have been introduced over the last few years in Premiere that I use heavily. Bulk operations for color/audio using 'Source' settings. Working in Productions mode rather than stand-alone projects. Other things.

Well ... I'd still say I'm not as good at cutting/trimming as so many others. But ... so many editors basically don't really know of or use the "bulk operations" that can so speed things along because ... well, no one in their shop does.

As a noted specialist told me last week, he's noted that for years. Because video post is so "siloed" that a high percentage of the very experienced pros in his many classes have never done most of the bulk production things.

People just do what they know will get this task done now. As they've always done it.

We humans are really best at well, being Human, it seems.

Neil

Report · Feb 02, 2023

Thanks for the answers. As the questions suggest what I'm trying to understand is:

Does the LUT do anything different to adjusting the controls in Lumetri colour?

Yes I know a LUT cannot be changed and I can only see what it did by looking at the affected clip.

Example I load a LUT into the basic section of Lumetri and it gives colour and brightness look "A" Let's say I can then remove this LUT and get the same look "A" with the Lumetri colour adjustments. Is this affecting the data in the same way?

I am sorry this seems to be such a basic question, it should be a yes or a no!

I hear people say "converting to Rec 709". I understand what Rec 709 is. However, the video file is a bunch of 0s and 1s. So this conversion is a nonsense, you're just affecting the data so it looks like Rec 709.

Thanks,

Jon

Report · Feb 02, 2023

BTW I am a very experienced professional editor and camera op, just new to LUTs and log recording.

Report · Feb 02, 2023

It's simple up until it isn't, right?

For a "look" type LUT, yes, that LUT doesn't do anything different than working the Lumetri controls to make the same thing. At that point, it may (or may not ... ) save you some time. And so can be quite useful.

Although the ones I make for that, I tend to save and then save a Lumetri preset, with that LUT applied in the Creative tab, and typically, no other settings set. Why?

Then I can drop that on a particular media type in the project panel in a bulk operation.

And for any clip where the LUT doesn't quite 'fit', as that preset will be applied as a "Source" effect, I can go to the Basic tab in the Source tab of the ECP ... and trim the exposure/contrast/sat to get the clip looking good.

AND I can use the "intensity" control for the Creative tab's "Look" section to up or lower the affect of that LUT on the clip. Win-win!

But there is one difference in a LUT over a straight preset to be aware of!

Lumetri by design tries to keep you from "breaking" your media ... they work to keep data from clipping/crushing with most controls. (Which, as noted, can drive experienced color people to seriously off mental states ... )

And when you make a LUT, or get one from somewhere else, that LUT may work great with some clips but cause clipping or crushing to another.

With a straight Lumetri preset, no LUT used, that is never a problem.

BUT ... if you apply a LUT ... even a "simple look-type LUT" ... in the Basic Tab's Input LUT slot, that can clip or crush data that you cannot recover later.

So ... hoping this helps with the fog!

Neil

Report · Feb 02, 2023

============

Example I load a LUT into the basic section of Lumetri and it gives colour and brightness look "A" Let's say I can then remove this LUT and get the same look "A" with the Lumetri colour adjustments. Is this affecting the data in the same way?

======

yes

Report · Feb 02, 2023

Super, thanks both.

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LUTs and Lumetric colour