That's the google search of the day for me.
I edited some footage last night on Premiere Pro CS5 (windows), exported it using the Youtube Widescreen HD settings. After waiting a few minutes to watch it, I was disappointed to how dull and washed out it looked compared to the screens in Premiere.
The search results got me to Video Copilot's blog, which had a way to adjust gamma-shift settings in Quicktime. This indeed gave me better viewing results. But I'll have to do more tests since I didn't have this problem before.
Here's their tip:
Using mp4 or h.264 when compressing through QuickTime can make the final video look washed out. This is a common problem that seemed to have no solution… until now. The gamma shift can actually be fixed inside QuickTime Pro without re-compressing your video by simply changing a few settings.
Scrimski at CGtalk.com posted a good walk-through. Thanks!
SOLUTION: After rendering into a QuickTime/h.264 file, open it up in QuickTime and select “Show Movie Properties.” Highlight the video track then click on the “Visual Settings” tab. Towards the bottom left you should see “Transparency” with a drop-down box next to it. Select “Blend” from the menu then move the “Transparency Level” slider to 100%. Choose “Straight Alpha” from the same drop-down and close the properties window and finally “Save.”