7 Replies Latest reply on Feb 6, 2018 7:07 AM by DMMax

    Reddish/Magenta color blocking removal?

    DMMax Level 1

      I am using a Panasonic GH5 with V-Log L profile and in my videos in the shadows and some other areas, there is reddish/magenta color blocks and I am unsure if there is a way to remove this as it occurs on a lot of my videos. I am using 4K ALl-I 400Mbps 10-bit 4:2:2. I found this video before which has helped remove other chromatic aberrations and color fringing:


      However, when I try to remove the reddish/magenta color blocking this way, it just ends up effecting all reds in the video, even ones I don't want changed. Here is an example that shows the issue. I too this video of a gull and as you can see on its chest beside its legs, it has this noticeable issue:


      This is an unedited screenshot of the video and edited version with a saturation boost and adding the Panasonic V35_to_Rec709 LUT::




      Here is close up of it and you can see the problem is there on the video, its nothing to do with what settings I apply on the video, first is unedited and second is edited:




      Here is a short sample clip of the edited video itself so you can see the issue on the video. As I mentioned the settings I added didn't cause the issue, only made it more noticeable. The video is in DNxHR 4K 10-bit 4:2:2 HQX. If you zoom in on the birds  chest, you can see the extent of the issue. Link: Dropbox - GH5_Gull1_Sample.mov  Download it rather than play it.


      Can anyone help?

        • 1. Re: Reddish/Magenta color blocking removal?
          Mylenium Most Valuable Participant

          Well, the tutorials is actually pretty amateurish and mostly useless. If you have to use extensive masking to remove CA, then you're doing it wrong. The real trick - as so often - is simply to transpose the channels individually and make the color components converge again. In your case you would use effects like Channel Combiner and Shift Channels to separate all the components, convert them to YCbCr, apply distortion effects like Optics Comepnsation and move the layer by tiny amounts, then apply secondary instances of the afforementioned effects to convert back to RGB and use Add blending mode on your 3 layer duplicates, each representing blue, green and red, respectively, to bring everything back together. Under ideal conditions this doesn't require any additional color corrections at all nor any of the atrocious workflows shown in the tutorial.



          • 2. Re: Reddish/Magenta color blocking removal?
            DMMax Level 1

            Hi Mylenium,


            Thanks, but how do you do what you said? I don't really know much about using After Effects yet and unsure to do what you said.

            • 3. Re: Reddish/Magenta color blocking removal?
              Rick Gerard Adobe Community Professional & MVP

              I downloaded your clip and took a look at it on a 10-bit 4K monitor at 800%. If you pause and look at a single frame there is a bit of a color shift in the gray part of the image.

              Screen Shot 2018-01-15 at 10.16.03 AM.png

              If the video is playing back at speed, even with a magnification factor of 800% it is nearly impossible to notice. My approach would be to simply open up Lumetrey color and use the curves section to desaturate the purple a little bit, then complete the rest of the color grading. Something like this will greatly improve the image and the color grading with about 30 seconds work.

              Screen Shot 2018-01-15 at 10.25.17 AM.png

              Which will take you from this:

              Screen Shot 2018-01-15 at 10.28.59 AM.png

              To this:

              Screen Shot 2018-01-15 at 10.29.21 AM.png

              By making some minor adjustments in the center Red Green and Blue channels to neutralize dial in the white balance, adding a slight S curve to the overall gamma to bring up the contrast, and putting a dip in the Magenta saturation. This makes the color fringe, which I'm not sure is caused entirely by chromatic aberration, almost completely disappear when looking at a single frame and invisible when playing back at full speed.


              If you really want to isolate those specific colors and neutralize them then it is going to require you to create a procedural matte based on the exact hues you want to change. Colorama is probably the tool I would use for that. Then you'll need to duplicate the layer, set up a track matte, apply the correction and desaturation to just those fringes, probably add in some hand roto so the other colors are not affected, and then composite the whole thing back together. In my never humble opinion, that would be a waste of time. Just a little color grading and a dip in the Magenta saturation on the whole image will remove nearly all traces of the problem from the video when viewed at full resolution playing back at full speed. You will go crazy trying to fix every frame. The only way to truly judge the quality of your image is to watch it at full speed. This looks pretty good to me:


              Screen Shot 2018-01-15 at 10.43.08 AM.png


              Screen Shot 2018-01-15 at 10.42.54 AM.png

              • 4. Re: Reddish/Magenta color blocking removal?
                Kevin-Monahan Adobe Employee

                Hi DMMax,

                What did you end up doing to solve this issue? Let us know.



                • 5. Re: Reddish/Magenta color blocking removal?
                  DMMax Level 1

                  Excuse the late reply, I haven't been well. Rick GerardI have looked at what you said, and I have found from doing what you have said, I have been able to correct the white balance in my V-Log L videos and it has reduced some of the color issue.


                  Kevin, so far I have yet have not been able to remove the magenta blocking which is the main issue I am having, but might have reduced it slightly, not enough to make it unnoticeable yet. I don't think its a chromatic aberration issue since it happens with whatever lens I use. It could be macro blocking from being a AVC codec. I don't know if this codec info from the videos will make a difference to what it is, but:


                  ID :1
                  Format :AVC
                  Format/Info :Advanced Video Codec
                  Format profile :High 4:2:2 Intra@L5.1
                  Format settings, CABAC :No
                  Format settings, GOP :N=1
                  Codec ID :avc1
                  Codec ID/Info :Advanced Video Coding
                  Bit rate mode :Variable
                  Bit rate :400 Mb/s
                  Width :3 840 pixels
                  Height :2 160 pixels
                  Display aspect ratio :16:9
                  Frame rate mode :Constant
                  Frame rate :25.000 FPS
                  Standard :Component
                  Color space :YUV
                  Chroma subsampling :4:2:2
                  Bit depth :10 bits
                  Scan type :Progressive
                  Bits/(Pixel*Frame) :1.929
                  Encoded date :UTC 2017-12-26 13:36:34
                  Tagged date :UTC 2017-12-26 13:36:34
                  Color range :Full
                  Color primaries :BT.709
                  Transfer characteristics :BT.709
                  Matrix coefficients :BT.709
                  • 6. Re: Reddish/Magenta color blocking removal?
                    Kevin-Monahan Adobe Employee

                    Hi DMMax,

                    Are you monitoring this image in a sequence which matches clip settings? Your video is quite small in comparison to, say, a HD frame size or even SD. The frame size (840 x 160) seems very odd and quite small. I'd start by shooting at a default frame size.



                    • 7. Re: Reddish/Magenta color blocking removal?
                      DMMax Level 1



                      Sorry for late reply, I have been busy. I am not sure what you mean about the video being small. My videos are UHD 3840x2160 as was the short sample clip I uploaded. I would have uploaded an unedited video to show this issue properly, but the file sizes are too large.


                      I was playing around with Lumetri colors and I found I could reduce the issue (its still there but a little less noticeable), if I set the Saturation to 300 to get the colors looking fine, then the vibrance to -20 it helped to reduce the strength of the blocking. I think there may be an issue with reds/pinks/megentas being oversaturated as they tend to be stronger than other colors in my V-Log L videos, but as yet, I haven't been able to solve the issue, except fix the white balance which I mentioned in my previous reply.