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stevens70907226
Inspiring
November 21, 2021
Beantwortet

Are LUTs and "Creative Looks" the same thing?

  • November 21, 2021
  • 2 Antworten
  • 8382 Ansichten

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,

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    Beste Antwort von 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 Antworten

    R Neil Haugen
    R Neil HaugenAntwort
    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 ...
      S
      stevens70907226Autor
      Inspiring
      December 2, 2021

      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
      R Neil Haugen
      Legend
      December 2, 2021

      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

      Everyone's mileage always varies ...
        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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