4 Replies Latest reply on Nov 5, 2010 7:47 AM by VFXgirl

    Colorspace for exported mattes

    VFXgirl

      I  work as a stereo compositor and find that I am often creating and  compositing elements in multiple programs depending on my needs. This  can get a bit confusing when trying to maintain the proper colorspace  and ensure that elements are composited with the matte as it was  intended to be.

      My questions are:
      What  colorspace is a matte that is exported from the alpha channel as a  .png? .png files are sRGB, should I assume that a matte exported from  the alpha channel is as well? even if the matte was created in a project  with logarithmic .dpx files or .exrs?

      If  a matte is created in the RGB channels (a black and white matte with no  actual alpha channel), would the exported file match the colorspace of  the file type that is rendered (sRGB if it is a .png)?, would the  colorspace be decided by that of the original source that the matte was  created from (log if it was .cin)? Or would the colorspace in this  situation be dictated by the project settings?

      Please  let me know if there is anything I have not made clear. Any information  on colorspace management specifically relating to creating and  exporting mattes would be helpful.

      Thanks a bunch!

        • 1. Re: Colorspace for exported mattes
          Todd_Kopriva Level 8

          You often don't want to color-manage mattes. You often want to preserve RGB values so that, for example, 0.5 is always 0.5 (exactly between black 0.0 and white 1.0). That's why there's a Preserve RGB checkbox in the output module settings.

           

          from After Effects Help:

          "You can prevent the conversion of colors from the working color space for a single output item by selecting Preserve RGB in the Color Management tab of the Output Module Settings dialog box. This option preserves RGB numbers; color appearance is not preserved. Turning off color management for a specific footage item is useful when the footage item is not intended for visual display, but is instead intended for use as a control layer—for example, a displacement map."

          1 person found this helpful
          • 2. Re: Colorspace for exported mattes
            Todd_Kopriva Level 8

            I supposed that I didn't really explicitly answer your question:

             

            Yes, if you import a movie (and that movie just so happens to be a matte), then that movie will be interpreted using a color profile just like any other movie. Just because a grayscale movie in DPX format happens to be intended to be used as a matte, it doesn't somehow prevent it from being interpreted differently from other movies in the same format.

             

            You can change the interpretation settings to assign an input color profile, and you can choose to preserve RGB values (i.e., not color-manage them).

            • 3. Re: Colorspace for exported mattes
              Mylenium Most Valuable Participant

              What Todd said... Alpha and transparency channels are for all intents and purposes linear and independent of the actual color space. Everything else just doesn't make sense, as it would make things like blending modes and otehr transparency calculations utterly unpredictable.

               

              Mylenium

              1 person found this helpful
              • 4. Re: Colorspace for exported mattes
                VFXgirl Level 1

                Thanks for the help guys!

                This clarify things a lot. Color management has become an issue at work as we add more compositing packages to our arsenal.