6 Replies Latest reply on Mar 3, 2016 8:36 PM by chrisw44157881

    Professional green screen question.

    Yiannis72 Level 1

      Hello friends!

       

              I am a visual artist and I have a question, in case someone of you out there knows the mystery answer...

      In this Vimeo link: Digital Idea Showreel 2016 on Vimeo you can see a Vfx showreel. As you can see the most green or blue backdrops are full of wrinkles and unevenly lit. I use Keylight plugin and Primatte Keyer with After Effects CC and Nuke. I do a good job but I cannot understand how they manage to pull a perfect key out of these backdrop settings. I suspect they pull multiple keyes. That's completely understandable, since I never pull just one key either. But still the wrinkles and bad lighting is something we all try to avoid. My other guess is something I also use... They pull the multiple keys and then enrich them with edge brushes like photoshop and other edge correction and lightwrap techniques. But still the only way to pull a totally photorealistic and professional key out of bad footage is a perfect compositing and ................ ROTOSCOPING. I think they just use the green screens just to isolate their forground and then they rotoscope the shιt out of it. Rotoscoping is something I HATE!!!

       

      Much obliged!

      Yiannis Stravolaimos

       

      Home - Yiannis Stravolaimos (Visual Artist)

        • 1. Re: Professional green screen question.
          Mylenium Most Valuable Participant

          yepp, that's just it. VFX houses have armies of roto artists.

           

          Mylenium

          • 2. Re: Professional green screen question.
            Yiannis72 Level 1

            Hello Mylenium!

             

                  So, I suppose there is not a super technique which can improve things, just hours and hours of detailed rotoscoping, after a decent key has been pulled... Oh God.. haha!!

             

            Thank you!

            • 3. Re: Professional green screen question.
              chrisw44157881 Level 4

              my post below is accepting the fact that you didn't have good lighting in the first place....

               

              1. most people shoot with the greenscreen in focus. you're supposed to use a shallow depth of field so AE can't see the wrinkles, fuzzies, etc. in the shot.

               

              2. each camera and each keyer has a sweet spot for the ire chroma levels.

               

              3. people shoot flat instead of neutral profile!

              flat is for grading extra f-stops at the expense of color noise, but in keying, you want lowest noise possible. profile: neutral, saturation 0 contrast 0 etc.

               

              4. and then the most ironic thing happens, people encode to lossy codecs and expect to pull good keys! fyi prores is not lossless, not even the hqx.

               

              I find it funny that no one talks about this.

              • 4. Re: Professional green screen question.
                Yiannis72 Level 1

                I totally agree!

                 

                When I shoot green screen footage, I shoot:

                 

                - In video mode (not in film mode) when I am inside of an indoor studio and in film mode when I am outside.

                - I shoot Raw so thre is no compression in the image.

                - I shoot with narrow depth of field in order to avoid wrinkles but almost all the time I use no depth of field at all so everything is in focus because I have to record the tracking markers on the backdrop, since if the markers are not crystal clear, I have broblems in tracking the shots in post.

                - I never encode the green screen footage. The golden rule is that you always work with uncompressed footage when it comes to keying.

                - I always denoise the footage (if there is any noise)

                - I color correct the footage so that the green has the right digital green color.

                 

                But still, if you want to have perfect composits, you have to rotoscope almost everything....

                • 5. Re: Professional green screen question.
                  chrisw44157881 Level 4

                  sounds good. although if you're tracking with markers(that would have to be in focus!), you'd usually have good lighting in the first place

                   

                  but what does "I color correct the footage so that the green has the right digital green color" ?

                   

                  1. -if you have a Red one:

                  grade on the r3d BEFORE exporting and keying. higher iso (1280), denoise, full debayer. (so you're not pulling shadows in the NLE!)

                   

                  2. -if bmpcc:

                  Take the DNG RAW, import as ACR with NO sharpening(default has hidden sharpening!), use a neutral BMD film LUT to Rec. 709. Be in 32bpc and setup color management.

                   

                  as a side note:

                  1. use neatvideo before keying badly lit footage. pre-render 10 bit lossless for speed.

                  2. run intermediate result out of keylight as alpha matte. its spill suppression creates noise, use spill on separate alpha'd layer only.

                  3. if using interlaced footage, always deinterlacewith a really good deinterlacer before keying or you're stuck with AE's deinterlace.

                  • 6. Re: Professional green screen question.
                    chrisw44157881 Level 4

                    first off, I've read Adobe's whitepaper on native r3d imports and I believe it has errors....

                     

                     

                    Namely,

                     

                     

                    interpreting r3d as rec. 709 and a working space Rec. 709. THAT would lose quality from REDLogFilm during the keying process because you need the same size or bigger colorspace to work in. Instead I say, use view simulate to Rec. 709 and instead, process out as REDLogFilm gamma at color management DCI-P3/Redcolor4/bt1886(Rec 2020).

                     

                     

                    So for an ultimate keying guide, this is what I have so far... please annotate any working bugs!

                     

                     

                    step 0 shoot REDLogFilm it follows the cineon spec precisely, +-0.5 f-stop, 60 Ire, Green as 18% gray, 5000k not tungston. unlike other methods, proxies will not work with keying. Native ISO of the MX sensor is 800, old Mysterium-X RED One is ISO 320, ISO greater than > ISO3200 there's some mild compression to fit all the code values in = quantization. under Tungsten use a 80c blue Filter but loses 1 f-top

                     

                     

                    1. in redcine-x, do a white-balance point native D60 while adjusting nothing else, denoise, Full debayer, REDLogFilm, Redcolor4.

                    2. in AE, chose DCI-P3/Redcolor 4/bt1886(Rec 2020) as the project working space and linear light for gamma 32bc, view-simulate rec. 709

                    3. import footage directly into AE as r3d, interpreted as REDlogFilm, Cineon converter log to lin

                    4. remove noise with neatvideo, sharpen off

                    5. put on keylight, increase green saturation AFTER keylight to view your work with use hue/saturation

                    if it looks good( just the alpha, not the color), then continue to next step.

                    6. Ignore spill suppression and color correction until later

                    7. use previous comp to alpha matte as a clean plate. Final step spill suppression, basic color correction, lightwarp etc.

                    8. render out REDlogFilm, colorspace DCI-P3/REDcolor4 or 64 cube lustre Lut redlog to bt1886(Rec 2020)

                    a. Tiff trillions color, cineon converter lin to log

                    b. 10 bit DPX Log, NOT 8 bit log or compresses bits

                    c. EXR linear light(log not needed in 32bpc space)

                     

                    as a side note: DNG's color profile is ProPhoto RGB