The Following are 4 shots all taken with a Canon 5D and 17mm, 70mm, 200mm, and 400mm lenses.
The camera was mounted on a tripod so all are the same view point.
On the right are the original file with no cropping.
On the left are the same File cropped to 62.5% to represent what you will get with the same lenses mounted on a Canon T1i or similar.

If you want a detailed explnation of the effect of sensor size click here