I’ve noticed that Quicktime with an H264 codec has this nasty habit of changing your video’s gamma. I’m not sure what the cause of this is. It might be my settings, it might be my computer, it might be whatever LUTs are being used, but I know it’s NOT my monitor. I have also reproduced the results on multiple computers, both mac and pc.
To measure this, I first made a test card to render out. The values shown are the actual pixel values.
Then, I rendered it out (of After Effects) into a quicktime movie using H264 and used ColorCop to meaure the new values. Next, I graphed the input-output results to get the gamma curve.
Using this information, I used a levels effect to create a compensation for the change imparted by the codec. The results after the correction are shown in red. Very close, but not perfect.
This is what the correction looks like on a normal image, it makes it darker:
Here is the After Effects Preset I made to compensate for this.
Hopefully I will eventually find out exactly why this is happening and fix it in a more elegent way.
