3D view background image size to fit lense?

Hi. I was wondering if there is a way to resize the background image as seen through 3D perspective view to the size of the camera lense, or if there is something else I can do such that I can compare a render (particularly in terms of camera placement and rotation) with an image. I have thus far put a plane with the image as a texture and with partial opacity in front of the camera and made the same size as the lense limits, but this way I have to re-render after each tweek I do, and I’m finding this will not suffice considering how much tweeking I will need to do. I need a real-time solution. Any ideas?

If I understand correctly, it sounds like you want the Blam plug-in for aligning the 3D camera to the camera used to take the photo.
Go into User Preferences and select the Add-on tab and do a Search for Blam. Check the little box to enable it.

This tutorial shows how to use it.

Steve S