Many of us sometimes try to take photo of whole building with one shot.Usually there is not enough space to do that, so photographer must tilt camera to take whole photo.

After perspective correction, straight lines become curves and instead rectangular building, you will obtain barrel shaped photo.Another way to solve these problems are to use Shift and Tilt lens for SLR cameras.Work is much better, effort is smaller but VIGNETTING is noticeable and sometimes unacceptable.

Curved lines are straightened somewhat, but they are not straight lines.These are optical problems and it cannot be avoided!Another thing should be considered is the price of these equipment.
Solution: Application Shift Lens 1.0 is developed to improve photos with these problems and you can correct curved lines to look like almost straight.
Curved or tilted subject can be straighten by one or two Bezier curves.