Yes, that makes sense - you want to do this:
Where the red cross (soz, jpeg blurred it) is the camera's focal point, the yellow box is the portion you actually want to display on-screen and the yellow cross is the centre point of the displayed portion.
But won't this cause problems when moving around? :
Imagine the two crosses are actually part of the 3D scene. If you gradually move the camera forward you will zoom in on the red cross. However, I think the viewer will see the yellow cross as the centre of focus, which will gradually disappear off the bottom of the screen as we get closer to the red cross. Do you see what I mean? Maybe this isn't a prob for you, I don't know.
Where the red cross (soz, jpeg blurred it) is the camera's focal point, the yellow box is the portion you actually want to display on-screen and the yellow cross is the centre point of the displayed portion.
But won't this cause problems when moving around? :
Imagine the two crosses are actually part of the 3D scene. If you gradually move the camera forward you will zoom in on the red cross. However, I think the viewer will see the yellow cross as the centre of focus, which will gradually disappear off the bottom of the screen as we get closer to the red cross. Do you see what I mean? Maybe this isn't a prob for you, I don't know.