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stevens70907226
Inspiring
November 21, 2021
Answered

Are LUTs and "Creative Looks" the same thing?

  • November 21, 2021
  • 2 replies
  • 8390 views

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,

    This topic has been closed for replies.
    Correct answer R Neil Haugen

    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

    2 replies

    R Neil Haugen
    R Neil HaugenCorrect answer
    Legend
    November 22, 2021

    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

    Everyone's mileage always varies ...
      Mike Dziennik
      Community Expert
      Mike DziennikCommunity Expert
      Community Expert
      November 25, 2021

      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'.

        Mike Dziennik
        Community Expert
        Mike DziennikCommunity Expert
        Community Expert
        November 25, 2021

        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


        quote

        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.

         

          Mike Dziennik
          Community Expert
          Mike DziennikCommunity Expert
          Community Expert
          November 22, 2021

          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.

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