Camera movement 'within one image'

Seems simple enough... and I know... AE101. But type that in and I can't find an answer. But I have one high res image painting that fits on screen. But... don't want to focus on full image but reveal it by showing certain portions only. Don't want to zoom in, that will pixilate it and blur it. Just want to move or fade in and fade out from one portion of the image to another.

Tried the Camera-Null combo in 3d space. Doesn't work, or I'm sure I'm doing that wrong.

How can I focus on one part of the image, then fade or move away from that portion to reveal the entire painting. Kinda like the stuff ya see on the History Channel...