l First, let’s ignore the camera body. Given a lens, and focus to an object. Then, you will get an image always at a certain position A, no matter which camera body you use.
l Secondly, let’s consider the camera body. The sensor must be located at the position A, no matter you use 30D or 5D.
The image is already there, processed by lens. Sensor is just a capturer, without any optical changes. So sensor of different size just capture image of different size. So a smaller sensor is just a crop of image, which is the same as in PS.
However, since 5D has a low pixel density compare to 30D, so with the same scale, 5D has less pixels than 30D.
Lens
28mm
50mm
200mm
Lens (x1.6)
45mm
85mm
320mm
View Angle
74°
46°
12°
View Angle (x1.6)
50°
28°
7.7°
Scale (x1.6)
67%
60%
64%
Pixels (x1.6) (Based on 12MP)
5.4MP
4.3MP
4.9MP