Vanishing Point Exchange - How to place the camera ?

Question

When I import a .vpe file into AE, I'm given a "custom" camera with an un(real)worldly focal length, and six-figure position and zoom values. My 3D scene is in extreme close-up.
My intuition is to give the camera a 35mm preset, set the zoom in real-world terms (I know,... I'm not in the real world anymore, Toto) and then move the camera position to my required start point.
I've been trying this, with multiple variations, all day and am getting nowhere - whatever I do results in either correct geometry at an unusable distance, or a nicely composed frame with unacceptable geometry. (I got lucky once early this morning - but have since been unable to repeat the result).
A question to those who, unlike me, know what they're doing: How should I go about this ??
Thanks !

Answer 1

That's
brilliant - thank you so much. This points the camera squarely at the
front vertical plane (in the real world terms of my scene, the end wall
of the hall). I'm no longer lost in space.
I then change the
camera Position Z-axis value to bring the camera closer to this plane
and ... Uh oh! the other four planes (side walls, floor and ceiling)
become stretched into a streaky blur. Where did I go wrong ?
If you want to post a screenshot, feel free to do it.
I suspect what you are seeing is a limitation for textures extracted from planes which have wild perspective shifts. When planes are more perpendicular to the "real" camera, the less actual texture information in the original, especially as pixels go further away from the camera. Zooming/orbiting with a 3D camera just makes this much more obvious So, there are some real world limitations when navigating pictures turned into 3D scenes in this way.
In clarification ... My final output is a QuickTime movie played from hard disk to a video projector. I work to a  frame size of 1400 x 1050 pixels to match the SXGA+ native resolution of my preferred projector (avoiding rescaling and loss of resolution in the projector). The size of my AE Footage image (in this case) is 5139 x 5433 to allow me to move my 1400 x 1050 frame around the footage to simulate camera movements. In the case of the "dolly in" towards the wall in my .vpe 3D set, 1400 x 1050 original pixels is the extreme limit of the movement beyond which I cannot go without interpolation and loss of resolution.
So to rephrase my question, with apologies for lack of clarity first time around, what would be a realistic limit to the pixel count of my footage image given the limitations of my system: 2.26GHz Quad-Core, 16 GB RAM and fast RAID ?
There should be no problems in such a case. In any case, just leave a couple of CPUs free in Memory and Multiprocessing, so that the other instances have more memory available to them.
(I've just ordered CS4, even though CS3 is more than adequate to my "aesthetic" needs, as I believe it offers better management of multiprocessing – and in the hope it will make my OpenGL problems go away.)
Multiprocessing in CS4 should be better, not worse. Sometimes "better" means taking a more conservative approach
In CS3, MP was more an "all or nothing" kind of thing, even if people used a buried text preference to turn off some cores. There are now officially supported management options for users.