Could someone explain to me why we can find diferent Depth-of-Field Tables (4x5, 5x7, 8x10) in the schneider' web page (www.schneideroptics.com) for a 210mm. lens ? I can't understand why the same focusing distance could give diferent dephts of field in the diferent formats of this tables. Ex.: 210mm. lens, f/4, we can rea d 128ft. to 447ft. in 4x5 and 94ft. to infinity in 8x10. Could it refers to a di ferent 210', (like an apo-symmar in 5x7 and a super-symmar in 8x10)? I'll be thankful for any help. Jose.