Michael I. Well-known Local time 10:24 AM Joined Aug 18, 2005 Messages 1,120 Location Israel \ Ireland View My Gallery Sep 20, 2005 #1 I know the guide number for 100 iso is 16(in meters)what is it for 50,400?
D djon Well-known Local time 10:24 AM Joined Feb 10, 2005 Messages 806 Location Albuquerque, New Mexico USA View My Gallery Sep 20, 2005 #2 For half 100 it's half 16 (divide by two). 400 is two stops faster than 100...and a stop is 2X, so your GN is four times sixteen with 400 film.
For half 100 it's half 16 (divide by two). 400 is two stops faster than 100...and a stop is 2X, so your GN is four times sixteen with 400 film.