To mere mortals like you and I it seems straightforward. If it's available in PS, then why not in AE? Unfortunately they're both built using different SDKs so it's a case of their starting from scratch - and also knowing about the particular needs of moving images, which in a computer is more than just an image sequence.
I've been talking to Photomatix about porting their HDR prog to AE (it is available as a plug-in for Photoshop) and they say it can't be done and the only way to use it for video is currently to batch process in the stand-alone version. Or, I would guess, in PS CS5.
Back to the thread's main subject - take a look at the Varicon to get a desaturated image in camera - I posted on another forum here about it.



