7 Replies Latest reply on Mar 13, 2015 8:50 AM by Dave LaRonde

    Background Chroma Key

    pauls51814723

      Hey guys,

       

      first of all sorry for my bad english I hope you understand what I want

       

       

      Is there a function in AE to subtract the background behind an object when I have the background without the object as well? (I want something like a chroma key, just for all without the object)

       

       

      For example:

       

      I have a video from a game with the character in front. Then I have the same video without the character. Now I want to delete the background so only the character is left on a black background.

       

      I tried all the effects like difference, subtract etc... but they don't work that well.

       

      Is there any effect that can do what I want?

       

      Thanks

        • 1. Re: Background Chroma Key
          Rick Gerard Adobe Community Professional & MVP

          If the pixels are exactly, and I mean exactly the same in your video without the character and your video with the character then you can use the difference keyer. If there are any compression artifacts or other differences this will not work very well.

           

          I am assuming that you are talking about game capture.

           

          Here is a little glossary that will help you describe your project by correctly naming the pieces.

           

          • Foreground plate: original video of a subject where you want to remove the background in someway
          • Background plate: video or an image you want to use as the replacement background
          • Clean plate: an exact copy of your foreground like that does not have the foreground element

          In your case the video without the character would be your "clean plate" if it is exactly identical to the video with the character except for the character.

          • 2. Re: Background Chroma Key
            pauls51814723 Level 1

            Hey,

             

            thanks. Yes I did this before and it works to 90%...

            The background completely dissappear because they are 100% identical.

            But because of the character is not the same, I have now a 20%-50% shader from the background in front of my character...

            So it is now perfect where it wasn't but the character that was perfect isn't after.

            Is there a option to disable it that the background overlays the character when there isn't the same pixels?

            • 3. Re: Background Chroma Key
              Rick Gerard Adobe Community Professional & MVP

              I would have to see the shot. Refine matte is probably what you are after. If it's game play video the color on the edges is probably very poorly blended with the background and the bit depth and anti aliasing is probably very bad and inconsistent so you're probably in trouble.

              • 4. Re: Background Chroma Key
                pauls51814723 Level 1

                I know it's a while now... but here is an example

                 

                1. I have a video of the Background:

                1.jpg

                2. I have a video with an object/character in front of the Background.

                2.jpg

                 

                3. I want now only in this case the angel.

                 

                With which function or effect can I subtract the Background so I'm just left with the angel.

                 

                Thanks

                • 5. Re: Background Chroma Key
                  Szalam Adobe Community Professional & MVP

                  Try the difference keyer as Rick suggested.

                  If that doesn't work, rotoscope it.

                  • 6. Re: Background Chroma Key
                    pauls51814723 Level 1

                    I already tried it but it doesen't work.

                     

                    You can save the two images and try it on your own.

                     

                    When I import them into AE and use the difference effect, all around the angel is perfect. But now everything from the letters "test" that was behind the angel is now in front of the angel... and I don't know how to fix it.

                    • 7. Re: Background Chroma Key
                      Dave LaRonde Level 6

                      If you're working in 3D, make sure the text layer's Y-position is behind the angel from the perspective of the camera.

                       

                      If you're working in 2D, make sure the text layer is below the angel layer(s) in the comp.

                       

                      In either case, this is REALLY basic AE knowledge, and you should take a step back:

                      Getting started with After Effects (CS4, CS5, CS5.5,  CS6, & CC)