9 Replies Latest reply on Feb 13, 2011 8:53 PM by UlfLaursen

    Green screen keying

    UlfLaursen Level 2

      Hi

       

      Not 100% sure how I do this - maybe someone kan help me out.

       

      I have a 1920 x 1080 50i project with some clips shot with green background.

       

      I of course want to apply the green screen filter on the green to cut out the person, but before that I would like to roughly cut arround the body to avoid stuff outside the green, and to "help" the keying filter.

       

      Is that possible, and if, how?

       

      Thanks in advance for any input on this.

       

      /Ulf

        • 1. Re: Green screen keying
          Colin Brougham Level 6

          Use one of the Garbage Matte effects; there is a 4-Point, 8-Point, and 16-Point version. Most of the time, I'm able to get away with the 8-Point version--fewer points to have to manipulate, which is good since you have to do them all independently.

           

          Apply your GB effect first, making it reasonably tight, and then use Ultra Key to pull the key. Don't rely on the default settings, but play with it a bit to refine the key--the settings aren't too difficult to understand. Use the Alpha Channel view in the Ultra effect to test how clean your key is. If you have a suitable GPU, all of this is accelerated, making keying a breeze.

          • 2. Re: Green screen keying
            UlfLaursen Level 2

            Thanks Colin

             

            /Ulf

            • 3. Re: Green screen keying
              UlfLaursen Level 2

              Just tried it out with the 8-point GB, and it works just great! Thanks again Colin

               

              /Ulf

              • 4. Re: Green screen keying
                UlfLaursen Level 2

                Ok, I have one challenge left now...

                 

                I have finished the keying and it looks good. I want to export the file as f.ex. DV AVI Widescreen including the alpha channel. The help file says this as the workflow for it:

                 

                "Export an AVI or QuickTime file with an alpha channel
                Select the sequence.
                Choose File > Export > Media.
                In the Export Settings dialog box, choose Microsoft AVI or QuickTime from the Format menu.
                On the Video tab, choose PNG, None, or Animation from the Video Codec menu, and choose 32 from the Depth menu.
                Set other settings and click Export or Queue to export as you normally would."

                 

                I cannot find any option on the video tab to choose any of the above settings. I must be doing something wrong.

                 

                Thanks.

                 

                /Ulf

                • 5. Re: Green screen keying
                  Colin Brougham Level 6

                  If you want to use Microsoft AVI as your Format, select "None" as the codec, and "32 bit" from the Depth option. If you want to use QuickTime as the Format, select any of the codecs that are suggested, and again set the Depth to "32 bit." It's the 32 bit part that is most important--it's specifying that you want your alpha channel saved into the final output as another 8-bit channel, in addition to the RGB (24-bit) channels that are already there.

                   

                  What you posted is actually a little misleading: it seems to say you have all these codec options for both formats, but for Microsoft AVI, "None" is the only viable option.

                  • 6. Re: Green screen keying
                    UlfLaursen Level 2

                    Awesome, Colin - you just made my day!!! Thanks a lot for your help, man!!

                     

                    /Ulf

                    • 7. Re: Green screen keying
                      UlfLaursen Level 2

                      One last question though... 

                       

                      Is it possible to draw a mask of some kind and only apply the green screen effect to that area? It turns out that the person I am keying out has some dark green spots on nis tie, and they tend to be removed when I apply the keying filter.

                       

                      Thanks.

                       

                      /Ulf

                      • 8. Re: Green screen keying
                        Colin Brougham Level 6

                        Yep, easy. It's called a hold-back or hold-out matte. Just place a copy of the subject layer above the keyed version, and use the garbage matte of your choice to "hold-back" just the parts of the image you want retained in the final composite. In your case, you'd create a rough outline around the tie; the first keyed version will have holes in it, but the duplicate on top will composite on to the background and be a seamless replacement.

                        1 person found this helpful
                        • 9. Re: Green screen keying
                          UlfLaursen Level 2

                          Thanks again, Colin