Complex sentence: They say the photo clearly shows searchlights focused on an alien spaceship; however the photo was heavily modified by photo retouchers prior to publication, a routine practice in graphic arts of the time intended to improve contrast in black and white photos.
Split into simpler sentences: They say the photo clearly shows searchlights focused on an alien spaceship. However the photo was heavily modified by photo retouchers prior to publication, a routine practice in graphic arts of the time intended to improve contrast in black and white photos.