3 Replies Latest reply on Feb 10, 2015 9:47 AM by Dave LaRonde

    Problem using linear workflow to composite images with nonlinear transparency

    minutephysics

      First off: I love what a fully linear workflow does for the proper behavior of gradients, transparency and the like.

       

      HOWEVER in both Premiere and AE I have found no simple way (within the linear workflow) to properly/accurately composite images that were not linear to start with/have nonlinear alpha channels. For example, I have an 8 bit RGB photoshop file with 2 layers: one with transparency and the other a white background. If I export the transparent layer as a png (or for that matter save it as a standalone psd), bring it into PP or AE and put a white solid behind it, it doesn't look the same as in the original photoshop file unless I turn off "composite in linear color".

       

      My best workaround so far is to bring the transparent image into AE (working in a linear color space) and manually adjust the gamma of its alpha channel using a combination of of track mattes/levels/shift channels effects to counteract the improper interpretation of the gamma of the alpha channel, since there's no effect or setting to change the linear/nonlinear interpretation of the gamma of the alpha channel.

       

      Is anyone at Adobe working on addressing this issue? Why isn't there an effect (or setting in "interpret footage") to allow us to specify if the source material has linear or nonlinear gamma? EDIT: I have just realized that there is a color management option in the AE footage interpret dialog (but not PP), but when I attempt to use it with a png it is greyed out/disabled.

       

      Thanks,

       

      Henry

       

      Message was edited by: Henry Reich