7 Replies Latest reply on Aug 14, 2012 7:09 AM by Pierre Devereux

    Chroma key question

    Pierre Devereux Level 2

      Hi,

       

      I was wondering if there was anyone around who might have some good chroma tips. This is the situation I am sitting in:

       

      I have sourced hundreds of Greenscreen books, and gone through them all. I understand that the most important step to pulling a good key, is lighting. The particular shade of screen plays a part, but the lighting of the screen is more important.

       

      I have several shades of green that I have tested, lit with daylight color corrected bulbs. The lighter shade reflects too much, and the Greenscreen specific shade (as per the place we bought it from) requires more lights to get an even IRE. All in all, my tests with the Green greenscreen have been pretty good. However...We have a character that is blue, and rather reflective. I dont seem to be having much luck with the greenscreen, so I wanted to try a RED or Yellow as a background to see how they work. Can anyone suggest the proper color red and yellow for me? I went and bought 3M of a red material (ok, more pink if I have to be honest) and trying to key that is like trying to pull chicken teeth! :-) the results are terrible - I have better results with the green greenscreen and working on the inside and edges seperately.

       

      I do understand very clearly that a one click key is virtually impossible, and that correct lighting is the "Key", to the um.... "Key"... - but I am also very aware that certain hues work better than others, as they are easier to light, or give less spill.

       

      So, after a long paragraph of waffle, I am basically looking for an actual colour name to go to a material store and buy a few meters of different colors for testing purposes. (one book specifies "Botanical Green" as the best "do it yourself shade")

       

      Thank you

       

      Pierre

        • 1. Re: Chroma key question
          Pierre Devereux Level 2

          Oh yes, to add,

           

          Has anyone had good experiences with using coloured bulbs to light their screens? Maybe a bright green bulb to boost the green of the greenscreen?

           

          Pierre

          • 2. Re: Chroma key question
            Szalam Adobe Community Professional & MVP

            If your blue guy is picking up green from the greenscreen, you might consider a contrasting light as the backlight/rim light for the blue guy.

             

            I'm sure others will have some further suggestions, but that was the first thing that came into my head.

            What keying tools are you trying to use?

            • 3. Re: Chroma key question
              Pierre Devereux Level 2

              Hi,

               

              I am using Keylight for the keying, and we have tried a magenta gel from above and slightly behind the guy to kill the spill. We also find that another magenta gel directly at the characters add a pretty nice colour to them. The problem is that this blue chap, seems to me to have a slight green tinge to him by default. Strange, I know, but I cant help getting a feeling of green colour in him no matter what light we use. This was the main reason I wanted to investigate some other background colours.

               

              Pierre

              • 4. Re: Chroma key question
                Szalam Adobe Community Professional & MVP

                People use red and magenta chroma screens all the time. I would think red would be perfect for your situation. What issues were you having? Also, you might try some of the other keying tools besides Keylight.

                • 5. Re: Chroma key question
                  Pierre Devereux Level 2

                  Is there a specific hue red or magenta?

                   

                  The guys went out yesterday and dropped by a cloth supplier and just bought a red cloth - although, to my eyes, it is more pink than red. When i try to pull a key using it, I get terrible edge issues. I am going to admit, that the lighting on the red screen might not have been 100%, as it has been a long day, and i shot it last - i might have skimped on some of the set up. I will have another go at it in the morning when I am feeling fresh again. But I am concerned that the cloth is not red enough.

                   

                  Which keying tools do you suggest? Primatte maybe? what else....

                   

                  Pierre

                  • 6. Re: Chroma key question
                    Szalam Adobe Community Professional & MVP

                    Pierre Devereux wrote:

                     

                    Is there a specific hue red or magenta?

                     

                    ....

                    Which keying tools do you suggest? Primatte maybe?

                    Specific hue? No, just the furthest from the blue you can get. Pure red would probably be ideal so that you only have color in one channel.

                     

                    Keying tools? Primatte? Yes. Others? Yes. Any/all. Test 'em! Try 'em! Find the best! Some jobs require different tools.

                    • 7. Re: Chroma key question
                      Pierre Devereux Level 2

                      Thanks man,

                       

                      Apreciate the advice.

                       

                      I think once I have a clearer head tomorrow, Ill run a few more tests and see whats up. I have sat and thought about it a nit more while we are chatting, and it occured to me, that I have been a bit of a twit as well (yes, this is known to happen from time to time) - The specific blue character was slightly out of focus due to an incredible depth of field in the camera we use (AF101) and as I said, I was getting a bit bushed by the time we shot him, so I dont think i had the optimal focus - blurry edges make for a difficult key to start with. Also, playing with the magenta gels with the ther characters, I turned the backlight off for him to test the effect of removing the Gel, and did not put the light back on without the gel when we shot him - Further compications due to there being a lack of nice contrast around his edges....

                       

                      So, once again, we find out the hard way that garbage in = garbage out! :-)

                       

                      BUT, i dont think this conversation has been a waste, and I will definitely look to some of the other tools, I know Mylenium has suggested a few to me in the past, I just never bothered, as Keylight has been sufficient till now. Also, I will try to get some more backdrop cloth of deeper colours to test with.

                       

                      Thanks for all the advice, one small step for me, one giant step for greenscreening!

                       

                      :-)

                       

                      Pierre