ZanQdo,
http://www.mir.com/DMG/aspect.html
the source pixel aspect ratio will be from AspX and AspY of your render settings in the format panel (the far right panel). ie AspX/AspY is your aspect ratio (default is 1, ie square pixels).
If you click on the buttons to the right side of that panel there are various preset aspect ratios and formats.
LetterRip
I am no blender user yet, but really like the idea of being able to use a free 3D pack to enhance my motion graphics and video comps in After Effects sharing camera data between them.
This is the closest to helping anyone “building the bridge” I can get…
Maya ASCII file format:
http://caad.arch.ethz.ch/info/maya/manual/FileFormats/FileFormats.fm.html
Python Computer Graphics Kit (Maya ASCII “.ma” import):
http://cgkit.sourceforge.net/doc2/node189.html
I would very much like to help in this project. I’m not a pro-coder, but i managed to write an simplistic exporter to the Autodesk Flame .action format. It was more than less a trial&error procedure, but now it can be used to import Blender-camera location-, rotation- and lensdata into Flame, and the vertices of a selected object become axis (what’s the plural? axises?). Now we can use voodoo through Blender with Flame…not that we would use it very often 
So as mentioned before I’d like to help, but I’m just a hobby-coder who never did some team-programming before. If anyone was able to write a script that generates a ascii-maya file that takes the Blender-data as input I could go on from there.
def write_maya-ascii(camLocX, camLocY, camLocZ, camRotX,…etc):
I could probably write that on my own, but I would have to work myself into that fileformat, and that could take me a long time. If someone would provide that i could pretty soon start some tests… But maybe we should first get an overview of what has already been realized and than synchronize our effords?
It would be so great if we could get that to work!!!
cheers,
knekke
knekke,
gosh, really? you wrote a blender to flame camera importer? flame, as in ex-discrete flame compositor? i’m impressed! is that script freely available (had to ask!)?
as i wrote previously, i’d be glad to offer any information possible regarding after effects.
–gt
Yes, flame, as in ex-discrete flame compositor. I haven’t posted the script anywhere, but of course you can have it. No guarantees given, because I would consider it alpha-status and it works only in PAL so far. HD1080 is in progress though. If you’re interested, I would write a little HowTo for that script, put some comments in it (it’s quite ugly a the moment ) and then post it somewhere or mail it to you.
You can set any aspect ratio that you want for Blender to output, but I believe the dafault is PAL (non square - European), but using square pixels required output for the script is probably a good idea as After Effects can then perform any necessary conversions.
ZanQdo, I’m P.M.ing you with some info from After Effects help files that you may find to be of some use.
P.S. If that info is not what you need then I can pack the entire help file in a rar cab and send it to you. Unpacked size is aprox. 26 MB Just pm me if you need more.
I decided to end this once and for all!
OK beta testers 
run this and tell me how it works! I still need to make sence of AE motion file… I’m not sure what is x y z pixels are or if Y is up in after or is it Z? anyway test and give feedback please
Hey ZanQdo-
cool thanks for the update on the script. Seriously thanks for working on this!
I used your script to export the camera data from blender and then renamed the export file to a .ma file instead of .txt When I try to import it into After Effects I get this message…
“After Effects: AEGP Plugin MayaImport: Only Baked Maya Ascii Files are supported.”
I’m by no means a After Effects expert… so I could be importing it wrong somehow. I just thought I would at least post this here in case someone else has the same problem. or maybe someone can tell me if I’m doing it wrong. I’m using AE7pro
thanks for the feedback, mmm I dont know about maya, if you can get me an example file of something that does import in maya, I can check it out 
please more feedback, lets finish this soon
Looking at Voodoo camera tracker Maya Ascii export file it looks like it might be Mel script. As I don’t know Mel I can’t be sure. Anyway Voodoo camera tracker creates Maya Ascii files that at least Eyeon Fusion imports without trouble.
Maya Ascii reference linked earlier seems to be best starting point.
Thanks for adding interoperability, ZanQdo!
seems to work here :
open the .txt in notepad, select all , copy…
go to aftereffects, select your camera, paste…
the main trouble will be the different XYZ orientations for world space coordinates between Blender and AE…
yes please give more feedback, I don’t know if I’m making my self clear, I don’t really know a lot about after effects… so tell me what is Up and what is right in AE if you can
Thanks for he camera tip he he I ill try do make my own scene with a camera in after effects XD
Weird issue here. After having copied the text, switching to AE returns this message:
After Effects error: invalid clipboard format - incorrect data (line261, near colum 0)
I’m using After Effects 7.1 and Blender 2.43
Below you may find the output.
thanks for testing!
HA HA HA damm un specific error :mad: ok maybe its becouse I’m using more pressition than affter effects can handle? I will try that…
you are right, there has been slight changes between AE5 and AE7 keyframe text format… but with a small manual tweak, zanqdo script does work here…
i was able to record IPO for the camera in Blender then edit the text file generated with his script + copy & paste it into AE7 keyframes to transfer the camera move …
But AE references layers in 3D space is a different coordinate system than Blender worldspace since it was merely a Z-depth system added over an older 2D layout with 0,0 being upper left corner…
doing true camera matching maybe tricky but i think ZanQdo has already done most of the hard work…
so, i am starting a little info file about what AE expects so that we can work on this…
Folks,
hope that you can bring this very important script to the community - indeed!
I’ve been waiting for this from a lot of time.
@ r3615: I don’t know how you managed to get it work, but good news!
Actually this could be the last step I’d need to finally get the chance to use Blender in commercial works, since our main tool is After Effects.
Thanks again 
I’m very glad so much people will find my exporter useful, but please give me the feedback I need to finish it, I’m a n00b in after effects, I can’t move without your help :o
yeah i get the same clipboard error dsp did. It feels like things are close to working here. Can’t wait!
The error is the the part of Location or in some rotation?