There’s the odd trouble that when you work in After Effects CS5 at one time, then have to go to CS4 later, that you’re stuck at the start again, since there is no backwards compatibility.

Technically, there still is no way, however, I stumbled upon a helpful way of half-doing it. There’s draw backs, but if you’re in a rut with your AE CS5 not going, and you need to finish some work now, you can save a little time by following this method.

http://forums.creativecow.net/thread/2/981933
The instructions are located at the bottom of the page.

Basically, what you’re doing is Exporting your file for Premier Pro.
Then when you open CS4, you just Import a Premier Pro file.
You’ll get a menu to choose what o import, but you’ll most likely be wanting the whole composition, so leave everything as default.
And hey presto, your works in CS4.

HOWEVER.

• Doing this does not restore your key frames.

• You will need to relocate your files without the help of the magical “After Effects has found X files that were missing” popup.
• Naturally, any effects or plugins for CS5 and up that aren’t in CS4, wont be available.
• Need to replace solids.
• Masks vanish.
• I found I needed to my effects back.

Now I did say there’s drawbacks, and looking at it from this point of view, if you had a large project with lots going on, you were better off starting again. But here are the time savers, and sometimes every second can count.

• Maintain the placement of all items within a composition.
• Comp settings will remain exact.
• Retain all folders you may have stored items in.
• Missing files will have “volume/(the directory your file was in)/ in their names, so if you’ve got large folder hierarchy of work, you can still locate it all.

That’s about it… it’s a sad list compared to the draw backs, but if you need to start again, but for whatever reason will be set back from CS5 to CS4, then this is just about the only way. All in all, the process takes a click of the finger to do, and once you sort out relocating files, you may have saved yourself half an hour (but it all completely depends on just how complex your Project management system is, and how complex the layout of say, cut footage sequences could be, since crop these down is unchanged though the transfer).

On my final note: If you’re even having to consider doing this to get work done, then I know your pain and feel sorry for you. So best of luck with meeting your deadline!

(ps: if you do test this, and discover something that I hadn’t noted, or perhaps something different occurred, please drop a comment here, and thanks in advance).

~Shea