Changing the Cinematographer’s Exposure Values in Post

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  • #170152
    Willian E. Aleman

      Hello everybody!

      It’s a convention among color grading tutors to teach colorist students to start grading by changing the cinematographer exposure values made on-set to match the camera manufacturer’s 18% middle gray specifications.
      This is a common practice when matching cameras shot with different manufacturers within the same film production. All exposure values are reduced to 18% middle gray.

      Should the cinematographer’s exposure —compensation— values in reference to18% middle gray be respected in post during color grading?
      In other words, does changing the cinematographer’s exposure value to 18% gray alter the technical and aesthetic creative decisions made on-set?

      Kind regards,

      Willian Aleman


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    • #170188
      Giovanni Louisor

        I think that beginning a grade by making sure all exposure values match the camera manufacturer’s 18% middle gray specs is completely unnecessary—there’s no sense in doing that, in my view. A cinematographer will have made deliberate exposure choices on set; such as choosing to overexpose, or underexpose everything (or certain scenes).

        There may even be some mistakes, or exposures that a cinematographer would want to fix in the DI: these should be discussed on that basis, with the colorist and the cinematographer. If adjusting the exposure in the DI is done correctly—by adjusting gain in linear gamma (as it does in RAW); it will match what can be adjusted with T-Stop; this is what it would alter—how that then effects the technical and aesthetic decisions, is something that should be considered, I think. If exposure is adjusted using gain in LOG (or on a Rec.709 transform) or in the Offset, it will affect the image in a different way.

        At the end of the day, the exposure should be adjusted in accordance to the taste of the cinematographer and the colorist, based on the context of the shot, and the overall film (or piece). I am no where near as experienced as you or everyone else here, but that’s what I would say about this!


          You can off-set logarithmic gamma similarly to RAW just the camera manufacturer itself then has no ‘say’ in redistribution of values.

          As you say when you adjust RAW values in the decoder its in a linear space (keep in mind, in RAW almost nobody still captures linear values, we just re-linearise the signal from its logarithmic container).

          You can do the same with a ProRes 4444 – non ‘RAW’ codec by applying the same mathematical transforms, it’s just a little jankier as most logarithmic equations have an EI aspect that you cannot adjust, so the signal redistribution is not the same as if its done with the manufacturers SDK.


          However, this does bring up an interesting subject – I recently had a series of cinematographers shoot on REDs and Sony’s for the entirety of a show, both claiming either looked better. I told production they were indistinguishable.

          We created our show look in the Log3G10 RedWGRGB IPP2 colour pipeline and I matched all Sony’s to Log3G10 RedWGRGB and the additional show-‘look’ was applied and was near indistinguishable.

          Just map out the transform with both cameras in near-identical settings as a test, make your corrects (I don’t do this in a colour NLE but rather a compositor) and it’ll be as accurate if not more than applying corrections after normalising signal and it retains artistic intent.


          Gabriel Devereux - Engineer


            I think you have to put this question into perspective.

            All productions are not the same and we are all at different stages in our working lives.

            The workflow is not the same with a famous DP who worked on a big production with a famous colorist who is also on set than a small DP who has no connection with grading process and no one is gonna bother asking anything on post production.

            So in my opinion to answer your question, it depends.

            In a perfect world all DPs should know how to shoot on camera for a final look and all colorists should know how interpret DPs and directors ideas to convey the message of the story with their grading.

            Personally I’m far of being a DP on big productions so I encounter this same issue you mention more often than not. To make sure production follows what I think is the look the story needs I do heavy camera reports where I specify all details about exposure, WB, power windows and as much details as I can as I rarely know who the colorist will be. But the reality I face more often than not is no one reads or listens what I have to say. Name it budget-time constrictions, colorists having no idea what they doing or my thoughts being discarded because they are bad.

            At my stage I rarely have any control of what I shoot once I left the set. Only on passion projects I can contribute and dialogue keeps going back and forth. It’s a shame that’s like that but this is what I’ve encountered at my level.


            Giovanni Louisor

              That really is a shame. I didn’t really consider the logistics of working on projects where there is little direct communication with a DP in relation to post-production.

              It’s unfortunate because, for both the cinematographer and the director, the relationship with the colorist is incredibly important—the final “look” of the film depends greatly on how it is interpreted in the color grading stage. It’s a major and, dare I say, definitive part of the work of a cinematographer; and to know that kind of creative control can be “held away,” in that way, really is a shame.

              I’m currently a college student, hoping to be writer and director (and to do my own cinematography and color grading), with very few projects under my belt, and everything I do permits that kind of control—due to working at a very low level. It makes me fear working on bigger projects: losing a certain level of creative control.


                I’d also say it depends. On the scale of the production and the ‘culture’. I’ve had colorists crank up my exposure to ‘see more’ despite killing all of the – clearly intended –  mood. I don’t even know who’s decision it was because in many productions I am out of the process once shooting is done.

                Roger said in this forum that he sits with the colorist through every single shot and overviews the decisions (very minor tweaks in general).


                  No, the colorist shouldn’t alter the color and exposure to neutral as a starting point, they should start with what the cinematographer created. If the scene had an 18% grey card in the shot under light that was intended to be of normal exposure and neutral color in the scene, sure… but that never happens!

                  Now I’m talking about the coloring the final cut. Sure, a test with a grey card or scale in it where the cinematographer says “time to grey card or scale”, especially when the test is comparing multiple types of cameras, etc. then yes.

                  In the days of film, I’d shoot a grey card or scale at the head of a scene and tell the dailies colorist to time for the card so that they would know what the neutral starting point was to judge my footage — otherwise if my footage was deliberately orange or blue, etc. they might correct it back to neutral without any reference frame.  But generally that approach isn’t done with digital since we have some sort of LUT as a starting point for dailies and monitoring.

                  Willian E. Aleman

                    Thank you very much to all responders. The collection of responses helps to clarify the topic.

                    Roger Deakins

                      One last comment from me. I would always shoot a grey card for film and in the early days of digital capture. But as David says, we now use a specific LUT and what I see on set will translates exactly the same on the colorists screen. For that reason I see no need for a colorist to ‘correct’ footage to match a spec..

                      Willian E. Aleman

                        Mr. Deakins, thank you for taking the time to comment on the topic.
                        As for all responder’s contributions, it’s greatly appreciated.


                        This is a very interesting topic. I do not think that adjusting exposure to the middle gray is a necessary step in the pipeline. I work in DaVinci Resolve.

                        If I work with different cameras, I convert them to DaVinci Wide Gamut / Davinci Intermediate, so middle gray of each Log is correctly remapped.

                        That said, I do change exposure and sometimes rather dramatically – but only after I discuss this change with the director. It happens with student films a lot, because students sometimes try to create all look in-camera and do not do it correctly.

                        Recently I had a film with heavily underexposed dark scenes and overexposed bright ones. I had to use noise reduction and change exposure rather dramatically, so the viewers can just see and understand what is happening in the first minutes. If these scenes were shot with correct exposure, I could have easily lower exposure in post, getting clean looking shadows and a lot of details.

                        The second reason for changing exposure in post is look creation. Usually look for the film is built around middle gray or midtones. We keep healthy contrast in midtones and add roll-offs and split toning in the highs and the lows of the image.

                        So, if an image is overexposed and is pushed in the highs, color contrast of the look dissapears. To avoid that, I sometimes increase contrast of the image by using Lift, so some part of it ended up in the lower region. And changing exposure also helps with getting the image “look-ready”.


                          I think in the situations you describe, key is what you said, to discuss more dramatic changes in exposure with the director and/or DP. Because sometimes things are really intended not to be seen. I had this issue a few times, where the colorist pushed the (low-key) image so that the viewer could better see what’s happening. But the intended purpose was to force the viewer to guess, not see, which was much more powerful.

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