Source : Webster's Revised Unabridged Dictionary (1913)

Photomechanical \Pho`to*me*chan"ic*al\, a.
   Pertaining to, or designating, any photographic process in
   which a printing surface is obtained without the intervention
   of hand engraving.

Source : WordNet®

photomechanical
     adj : of or relating to or involving various methods of using
           photography to make plates for printing