Fun with Gamma and Quicktime

gamma shiftHere’s a scenario being replayed at studios around the globe: The decision is made to upgrade to After Effects CS3. A big project comes in. All proceeds quite well until it’s time to render for final output, at which point files coming out of After Effects – particularly those being edited in Final Cut Pro – appear darker, even when rendered with a codec traditionally thought to be “safe” for gamma such as Photo-JPEG or even Animation (as was used to create this image). Howls of pain and gnashing of teeth ensue, After Effects is blamed, and in at least one case the entire studio reverts to 7.0. True story.

Don’t let this happen to you, folks.

Although there are various permutations of this problem, it generally comes back to rendering Quicktime movies directly from After Effects. “Why is After Effects messing with my Quicktime output?” you might ask. “Why doesn’t it just work like in previous versions?”

The short answer is that a simple checkbox may help you. Open Project Settings in After Effects CS3 and under Color Settings, toggle Match Legacy After Effects Quicktime Gamma Adjustments. This causes After Effects to work with QuickTime movies the same way as previous versions of After Effects. Boom. No need to set a Working Space or mess with gamma in any other way.

The longer answer is that gamma in Quicktime has essentially always been unpredictable for a couple of reasons: Apple changes the gamma according to their perception of how you’re viewing it (i.e. which platform you’re on, whether it’s a web codec, and what application is being used) and, being Apple, they haven’t published their gamma settings so that anyone else knows what the heck is going on, other than empirically.

Oh, don’t get me wrong Apple, I’m typing this on a MacBook Pro running Leopard, an iPhone at my left hand, Mac Pro behind it, ready to send this post via Airport Extreme.

I will likely have more to say on the subject of color management and I/O in After Effects, also a huge topic for the new edition of the book. Meanwhile, please freely post your horror stories (or revelations) here and I will scan them for more specific points to address. There’s also more to say about Quicktime and how it handles (or doesn’t) things like aspect ratio.

If you’re feeling bitter, boycott Quicktime until Apple and Adobe work this out together and use image sequences instead, like your pals who are film professionals. Otherwise try that checkbox and let me know how it goes.

By the way, here is a post from FreshDV a couple months back showing another culprit feature for unpredictable Quicktime gamma, in Quicktime 7.2′s very own preferences.

30 October 2007 | after effects | Comments

4 Responses to “Fun with Gamma and Quicktime”

  1. 1 Martin Westin 30 October 2007 @ 2:25 pm

    We had these kinds of problems on previously “safe” codecs this spring on a project. The gamma shift occured when exporting files to Quicktime in Windows and then working on them in After Effects (7) on a Mac. Shake “interpreted” the files correctly.

    The twist, and reason I post a comment, was that when pulling the gamma back and comparing to the original you were not back to the original “look”. There was some aditional color shifts that were found to be the result of the specific ColorSync calibration used on the Mac in question. Copying that profile and using it to “convert” the file back to the original sRGB space landed the files back to their original look.

    The Mac’s ColorSync was rendered as part of a QT-file in After Effects. To me that is on the bug-list and could not be a desired feature in any workflow I can imagine. ColorSync to me is like tweaking the EQ controls on my sound-system… I do not want my audio-files to be altered by that either.

  2. 2 mary james 3 November 2007 @ 6:03 am

    How should I export an image sequence per your suggestion in the article?
    Thank-you.
    MJ

  3. 3 Jonas Hummelstrand 4 November 2007 @ 7:31 am

    MJ,
    Image sequences are not affected by QuickTime’s peculiar handling of gamma, so you won’t be affected if you export to (my favorite) TIFF sequences. Be aware though that PNG sequences have issues.

  4. 4 Corey Culp 4 November 2007 @ 4:30 pm

    Thanks for bringing this up, Mark.

    This is a complication that hinders all apps that use Quicktime. Over at reduser.net, the users that are posting h.264 exports of their Red footage (through FCP) are producing gamma shifts that only seem to be seen on Macs, while their PC counterparts play these Quicktime movies void of the gamma shifts.

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