From PanoTools.org Wiki
Revision as of 00:00, 24 March 2005 by Erik Krause
Roll is the angle of camera rotation around it's optical axis.
If your camera is not level this can be in two directions:
- the image is tilted up or down, resulting in a Pitch value different from 0.0
- the image is rotated such that the horizon is not horizontal if held upright, resulting in a Roll value different from 0.0