7 Replies Latest reply on Oct 13, 2009 5:38 PM by Cris is Bliss

    having a real difficult time with Key Light

    Cris is Bliss Level 1

      I'm reading Mark Christiansen's After Effects CS4 Studio Techniques and Ive read the section on using Key Light 5 times and still cant get a key like his examples.  I'm trying to conquer two things that just are seeming impossible. One to retain the whisps of hair blowing in the wind and 2, to get rid of the green spill on the edges.  I've tried the 3 Pass Method, which he does not very cleary explain,and I cant get the edge matte that it is supposed to produce.  He leaves some of the important infomation written in the side notes, and other things are just plain confusing and he does not make clear reference to the examples on the DVd.


        Can anyone help me conquer this keying or at least point me in the direction so that I can learn this Step by CLEAR Step.



        • 1. Re: having a real difficult time with Key Light
          Adolfo Rozenfeld Adobe Employee

          What items are you using as sources, example files on the book's DVD?

          • 2. Re: having a real difficult time with Key Light
            Cris is Bliss Level 1

            I was using my files.

            The example files from the book work perfectly when turning the them on and off.  What I will try this evening is to import one of my clips into his demo files and adjust it side by side as he has done to his and see if I get the same results.  One of the problems is that he does not clearly or specifically make references (step by step) to his files.  He says things like Add a layer but he does not specify, for example, if the added layer is a duplicate if the existing layer 1 or layer 2.  Then if in the previous sentence he had you turn the View mode to Intermediate, he doesnt specify if the new layer shoulb be in the same view mode or in Final.  Then when reading the little notes on the side you discover that the Blend mode was supposed to be set to Stencil Alpha.  I guess if I was more familar with keying some of these would be common sence knowledge.  Lastly he had obtained an edge matte but did not explain the best layer order of the 3 mattes.  I'm guessing that the Edgematte is supposed sandwiched between the Garbarge and Core Mattes


            Or was the Edgematte to be used as a tracking matte applied to the GarbargeMatte and the CoreMatte placed on the top.


            Again Im new to this and it gets a bit confusing


            Thank you for you assistance.

            • 3. Re: having a real difficult time with Key Light
              Todd_Kopriva Level 8

              I just talked with Mark, and he mentioned that he simplified this part of the book for the CS4 version. Do you also have the CS3 version? If so, you might check to see if it has more detail.


              Peachpit Press still has a free excerpt of the CS3 book on their website, and it appears to be the section about Keylight. Maybe it has what you need. (I have to run to a meeting, so I can't check right now.)

              1 person found this helpful
              • 4. Re: having a real difficult time with Key Light
                Cris is Bliss Level 1

                Thank you Todd, for that link and your help.  I will try it this evening along with some other side by side tests.


                I hope its not another night of being up till 3am in the morning trying to figure this out.  ADobe licenced KeyLight for a reason, I just have to learn it.



                • 5. Re: having a real difficult time with Key Light
                  Cris is Bliss Level 1

                  I checked out the link you sent me, BUT still Im not getting it to do as he had.


                  1. I was reading through the forum on subjects that mentioned KeyLight and read something about that KeyLight needs to be applied to a Pre comped  Layer or is it KeyLight is applied to the layer inside the pre comp.


                  2. Even though I can't get that isolated edge, I don't fully understand how do I use it once I do get it.  Am I to apply just the refined Edge as a Luma Matte???  Or do I combine (pre-compose) the Core, Garbage and Edge mattes together and apply that as a Luma Matte to the original footage.


                  Thank You

                  • 6. Re: having a real difficult time with Key Light

                    Hi there,


                    The principle here is simple - it sounds as though the execution is what's tripping you up.


                    First, let's get the principle straight. The whole reason to do this is to avoid using Keylight for anything but your edges in order to give them the subtlest possible threshold. This means breaking apart the image, and the most elementary way to do it is to start with three passes: a garbage matte to get rid of background noise/rig that doesn't cross the edges, a holdout matte to get rid of holes in the matte, and finally the edge pass. In more complicated shots it is necessary to break the image down further, for example doing one edge pass for hair and another for the body, etc.


                    So you can start by just applying Keylight and creating your key.


                    What I have you doing if that doesn't simply solve your key is to spread the resulting matte (using Simpler Choker with a negative value) so that it's well outside the edges to create the garbage matte. In the previous CS3 version of the book I instructed that you do this on a separate layer and use Stencil Alpha blending mode to apply the result to the layers below, one for the edge matte and one for the holdout matte. You can still do it that way if it's clearer.


                    Otherwise, on a single layer the steps are

                    1. apply Keylight, refine the matte and then leave the View menu set to Intermediate Result - that's important, it insures no color shift


                    2. spread the matte with Simple Choker, set to a negative value (usually in the low double-digits)


                    3. apply Keylight again to get your edge matte


                    And after that, if there are holes in the matte, fix them by masking out a separate layer of the same source, below all of the others.


                    I hope that helps.


                    Mark Christiansen

                    Author, After Effects Studio Techniques

                    • 7. Re: having a real difficult time with Key Light
                      Cris is Bliss Level 1

                      Thank you very much for responding to my post.  Its an honor to communicate with you.  I will try as you suggested.  I'm sure part of the problem is my unfamiliarity with mattes and keying and how they work together.


                      Your book has been very helpful in learning how to use After Effects.


                      Thank you Again


                      Cris is Bliss

                      Rough Luxury