Rob Bernhard , Mar 11, 2011; 11:15 a.m.
The focal length of lenses do not change. The focal length is a physical property of a lens.
What changes is the field of view. The 4/3rds and m4/3rds sensor size give you a field of view of 2x that of the focal length. A 14mm lens on a E-PL1 will provide the same field of view as a 28mm lens would on a camera with either a full-frame digital sensor or 35mm film.