Today I assisted a TV channel in Greece with an After effects <-> Media composer 8.5 workflow and came accross some behaviour which I fear are bugs or design flaws. I hope Job ter Burg, the expert on these issues can verify.
After effects HD 1080i project with graphics for TV trailers. Render settings are Codec DNxHD120 8bit RGB + Alpha and inside the DNxHD codec settings also selected RGB so After effects changes the video levels of the already legal colours.
Fast import into Media composer with perfect results. Video levels are correct. This is the desired workflow. Everybody happy 
!
Then tested, out of interest, if the color levels setting in MC work by selecting "Scale from full range to legal range", just to test if they work. With these settings selected a normal (non fast) import starts, as expected, but the result is... exactly the same. No RGB ->709 scaling done. Why? Bug1?
Then I tested if AMA linking works to the same Matte key export from After effects. And gues what? It does link, shows an AMA linked matte + key and it does key correctly on a timeline! Bravo Avid! But unfortunately there are performance issues (red and yellow) when playing the graphics thx to the quicktime AMA plugin. Probably because the AMA quicktime plugin decides to perform a, not needed, 709 -> RGB scale transformation resulting in clipped whites and enhanced illegal colors. This makes very little sense in a 1080i50 YCbCr709 project, only if it were a RGB709 project if you ask me. Bug2?
So I do a right click on the AMA linked matte + key clip inside the bin to change the source settings but... they are greyed out similar to the imported matte + key clips. For the AMA linked matte + key clip this makes no sense to me. Bug3?
My conclusion of these tests is that Media Composer 8.5 (and maybe others older versions as well) is not capable of RGB ->709 correcting AE DNxHD matte + key full swing RGB clips while the import settings are there but do not work and the source setting when AMA linking are greyed out. So one has to make sure that levels coming out of AE are correct for YCbCr709!
I will do more tests to see if others codecs like animation and PNG also show this behaviour. But I would like to ask if others (Job) see this as well?
Kalispera.