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  • Exposure questions

    Hi There,

    As far as I understand, exposing for 100% Zebra should give us the most information in the blacks and causes no clipping at all, so it seems to be the perfect exposure. Is this the case? I don't think so, but I can't figure how. And whats odd:

    - When exposing for 100% zebra, nothing should be clipped, as far as I understand. However, when connecting an external SDI-Monitor with scopes, the waveform indeed clips. How is that possible?
    - No matter if I'm shooting Film or Video, ProRes or RAW: When I expose for 100% Zebra, it's drastically overexposed for my eye, and I can't really judge the shot. In my understanding, all of the information could be brought back in post, but it's really difficult to judge your shot when you're looking at a camera screen that's mostly white.

    Could you help me clearing these matters?

    Thank's a lot,
    Remo

  • #2
    When you say "expose for 100% zebra", you mean setting your zebras to show 100% IRE, and then setting your exposure to where you see no zebras at all right? I've always used this method and haven't had a problem.

    Comment


    • #3
      And just to piggy-back another question: Should there be absolutely no zebras showing with this method, or is it okay if a few very small specular highlights are showing zebras? I'm going to assume there should be no zebras...?

      Comment


      • #4
        Originally posted by Danny1280 View Post
        And just to piggy-back another question: Should there be absolutely no zebras showing with this method, or is it okay if a few very small specular highlights are showing zebras? I'm going to assume there should be no zebras...?
        In most cases with zebras at 100% I've always exposed to where no zebras show to guarantee all detail, but I know there are certain situations where you'd want to let certain highlights blow out, and you won't want that detail anyway.

        Comment


        • #5
          Here is what I have found:

          With Raw:

          1. Nothing should ideally be clipped according to the BMC screen, if you output to a monitor in then it kind of depends on the monitor, it might apply it's own LUT or whatever depending on what you use.
          2. Nothing should ideally be below about 15% in your waveforms, because these dark areas will become noisy. Depending on what you find acceptable, this could be 20% or 10% or another value.

          You will often find that you have to balance between 1 and 2. An easy example is at night by blowing out lamps and other light sources. If you don't let these clip, most of the rest of your footage will probably be dark and noisy, even with the BMC's high dynamic range. Sometimes during the day it can be a bit harder to decide. You don't want to blow out your sky, but your subject is in a dark shadow, even the BMC can struggle here. ideally you adjust your lighting with a ref or strong lights.

          Finding solutions to satisfy point 1 and 2, and choosing the right balance between them, is the key to healthy exposures in the BMC IMO.

          That's the relatively easy part, compared with the actual art of lighting

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          • #6
            The reason that an external monitor is different is because of your display output settings. The in camera zebras are always for the RAW data. It shows when the sensor is clipped and not when lut adjustments are clipped. Video mode is a lut on the log signal to make the image look normal in a rec709 space. That requires pushing the highlights up so if your RAW signal was close to clipping, the video mode output will surely be clipped going out the sdi if you are set to video mode. If you set to film mode for the video output the signal going through the sdi should match the zebras.

            This exposing to the right just under clipping is not good advice as far as I'm concerned. You can over expose by one or two stops, but if you go over 4 stops, how will you see your image? You won't be getting more noticeable cleanliness in the darks and your tonality will be effected. Just expose normally and you will get great results and not look bad when you send your footage to the editor.

            Comment


            • #7
              I believe the BMC SDI output is always film, and cannot be set to video. It is something that a lot of people had wished to be different.
              Possibly you can get a video output when RECORDING to prores video mode, but I never do this so I am not sure.

              In my case I adjust the monitor's contrast, brightness, and chroma, so that I get an image that is easier to focus. I keep in mind that this is not at all the image I am recording in terms of exposure. I rely on my waveform and scopes for that.
              It is a more technical approach, but I have found that it is more error proof in terms of exposure. Especially at dark scenes, even the BMC's screen can be very deceiving.

              Comment


              • #8
                Originally posted by drgeneric View Post
                Hi There,

                As far as I understand, exposing for 100% Zebra should give us the most information in the blacks and causes no clipping at all, so it seems to be the perfect exposure. Is this the case? I don't think so, but I can't figure how. And whats odd:

                - When exposing for 100% zebra, nothing should be clipped, as far as I understand. However, when connecting an external SDI-Monitor with scopes, the waveform indeed clips. How is that possible?
                - No matter if I'm shooting Film or Video, ProRes or RAW: When I expose for 100% Zebra, it's drastically overexposed for my eye, and I can't really judge the shot. In my understanding, all of the information could be brought back in post, but it's really difficult to judge your shot when you're looking at a camera screen that's mostly white.

                Could you help me clearing these matters?

                Thank's a lot,
                Remo
                100% zebra shows you what *IS* clipped.

                If you have Zebra's then you have clipping.

                You use the 100% Zebra to indicate where the clipping is and then YOU as the DP decide where the clipping point should be. Ideally, you shouldn't have clipping on important visual information.

                jb

                Comment


                • #9
                  What John said.

                  Also mind, that even if all zebra is just away (a hair below clipping), single channels still can clip, even if you don't see zebras..
                  Most of the time, this is fixed with the "recover highlight" check-box in Resolve though.

                  Maybe I start seeing things, but I'm under the impression, that with the last update, the was the "iris" button works was changed.
                  Before it was like, when you hit the iris button, your zebras just want away. Now it seems to stop down a bit more, to prevent single channels from clipping.

                  You can try that. ND or stop down, till the zebra disappears, than hit iris, and you gonna see that it stops down a bit more now.

                  Frank
                  Blog: http://frankglencairn.wordpress.com/

                  Comment


                  • #10
                    It's my experience that when your levels are below around 50%, you get noise in the image. On my SmallHD monitor when using False Color, if something in the frame is not ORANGE which is the skin tone level around 50%, there is noise in the image that may or may not be acceptable. How acceptable it is depends on what you're shooting. If you're shooting a beauty video, it might not be acceptable. If you're shooting a film, it may be, depending on your tastes.

                    I'm still using the firmware from Feb 2013, as I have not updated my camera. It may have changed since then, but I doubt it. Ultimately, you have to test to see what is acceptable for you and your project.

                    I've had in depth discussions with people who don't like the noise, and think that 50% level is way too high. Some have asked me what the point of having 13 stops of DR is if everything below 40-50% on the scopes is noisy. Some don't mind the noise. Depends on your taste and you have to ask yourself if that's acceptable or not.
                    Paul Del Vecchio - Director/Producer
                    http://www.PaulDV.net
                    https://vimeo.com/channels/directorpauldv
                    http://www.youtube.com/user/pdelvecchio814
                    http://www.twitter.com/pauldv

                    https://www.facebook.com/pages/Paul-...io/58731646898

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                    • #11
                      Definitely to taste, but if fifty percent is where one's tolerances sit this is far from the ideal camera.

                      So the same for the most revered digital image right now, Alexa, which is only SLIGHTLY cleaner raw-to-raw image.

                      FS100, C300, EPIC, F55 are cameras that people may want to look at if the noise is too much. I've noticed that each of those are fairly clean in most circumstances, the Epic @ 5K can be noisy yet when mastered at 2K with appropriate NR it pretty much vanishes. And, of course, FS100, C300 for those that don't want to remove noise in post. Cameras that do the work for you. Too many choices.

                      On Zebras: wonder if any of the BMD Engineers can confirm that 100 percent does not represent when any one channel clips. And, technically, if "highlight recovery" restores the clipped area, then it was never clipped to begin with? I just stick with the 100 percent for RAW and ProRes, and try to keep anything important from riding lower than 80 IRE.

                      SKYPE (best way to talk to me): Camera_Kholi | twitter
                      Avery and Pete: Superseeds Feature Film Trailer

                      Comment


                      • #12
                        Originally posted by Kholi View Post
                        Definitely to taste, but if fifty percent is where one's tolerances sit this is far from the ideal camera.

                        So the same for the most revered digital image right now, Alexa, which is only SLIGHTLY cleaner raw-to-raw image.

                        FS100, C300, EPIC, F55 are cameras that people may want to look at if the noise is too much. I've noticed that each of those are fairly clean in most circumstances, the Epic @ 5K can be noisy yet when mastered at 2K with appropriate NR it pretty much vanishes. And, of course, FS100, C300 for those that don't want to remove noise in post. Cameras that do the work for you. Too many choices.

                        On Zebras: wonder if any of the BMD Engineers can confirm that 100 percent does not represent when any one channel clips. And, technically, if "highlight recovery" restores the clipped area, then it was never clipped to begin with? I just stick with the 100 percent for RAW and ProRes, and try to keep anything important from riding lower than 80 IRE.
                        Yeah we've talked plenty about this before. I've had a director tell me he thought the image was noisy even after we pumped a lot of light into the scene and he was getting frustrated. He even questioned my knowledge of the camera saying that I must have a setting wrong. I told him to take a look at the settings because there barely are any. It just needs a lot of light. All of this was discussed before the project, but I guess it still took him by surprise. He kept comparing it to his Nikon DSLR though. Eek.

                        It really depends on how you rate the camera. For me, I set the ISO to 200 and shoot like that because that allows me to see what I'm shooting a bit better than keeping it at 800, which will look very "white." Someone correct me if I'm wrong, but if I'm shooting RAW, it still is a fact that shooting at ISO 200 does not decrease your dynamic range, it just displays it differently, correct? I know there was some back and forth about different curves being applied and whether or not you lost dynamic range, so I'm just double-checking my facts here. Either way, what I've been getting with the camera set to 200 is amazing and without a LUT, that's the best option to actually see what you're shooting.
                        Paul Del Vecchio - Director/Producer
                        http://www.PaulDV.net
                        https://vimeo.com/channels/directorpauldv
                        http://www.youtube.com/user/pdelvecchio814
                        http://www.twitter.com/pauldv

                        https://www.facebook.com/pages/Paul-...io/58731646898

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                        • #13
                          I don't think 200's been confirmed but to be honest I feel like there IS a difference when shooting 200, and so even when I'm doing a sort of "Viewing lut" approach by changing ISO, I stay at 400 or 800. But, might be me playing tricks on m'self. 1600 ISO is definitely changed.

                          By using the TV Logic with a fake look on it, I've been able to judge what's too far under and what's not, and have been getting cleaner images since.

                          His Nikon DSLR is definitely going to be cleaner, given that it's reducing noise (and IQ in general) when going to a compressed image. I guess I'm being redundant, sorta feels like anyone afraid of noise to that degree would never shoot Alexa or F65, F35, or Film for that matter. xD

                          SKYPE (best way to talk to me): Camera_Kholi | twitter
                          Avery and Pete: Superseeds Feature Film Trailer

                          Comment


                          • #14
                            Originally posted by Kholi View Post
                            His Nikon DSLR is definitely going to be cleaner, given that it's reducing noise (and IQ in general) when going to a compressed image. I guess I'm being redundant, sorta feels like anyone afraid of noise to that degree would never shoot Alexa or F65, F35, or Film for that matter. xD
                            Definitely. I keep referencing The Village and 28 Weeks Later. I like the way they're shot. Whether you like the films or not, check out how much noise is in the image. It's WAY more than what I normally get out of the BMCC, especially in 28 Weeks Later. I believe 28 Weeks Later was shot on Super 16 for the majority, with VFX plates shot on 35.

                            I really wish there was a way to view the image at 200 without actually changing the setting. I know it's been talked about a lot, but it would be awesome. If 200 truly doesn't affect the image, then I'm fine with just setting it to 200.
                            Paul Del Vecchio - Director/Producer
                            http://www.PaulDV.net
                            https://vimeo.com/channels/directorpauldv
                            http://www.youtube.com/user/pdelvecchio814
                            http://www.twitter.com/pauldv

                            https://www.facebook.com/pages/Paul-...io/58731646898

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                            • #15
                              Shooting prioritizing your clipping point rather than middle grey is weird to me. Sacrificing 2 stops of light to just see your image seems like a little much. Noise reduction would be a far simpler if thats a subjective problem, especially since the BMC is usually too sharp anyway. I know the bmc is strong but I would rather clip than have the contrast ratios on the talent be ambiguous.

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