The correction of camera optics distortion and sub-pixel method for image processing can reduce the error of target image orientation for the precision improvement of system measuring.

To sum up it has to be said that if it is possible to use a reflex camera - it is great, as they have large matrices with little rate of noises, removable optics and safe RAW format.

Some of this light would then travel back to the door and be reflected into the camera. That much is basic optics.