Perspective Control
Prepared 2006-01-30 (173/43187#4) by Bill Claff

Here is a Photoshop technique that works well in many situations:

1. Upper left - use Crop Tool to locate the verticals
2. Upper middle - move the lower corners of the crop to the corners
3. Upper right - move the top corners of the crop 1/2 way to the corners
4. Bottom - the result

This 1/2 rule works because usually you have pointed the camera up about 1/2 way instead of keeping it level.