Archived posting to the Leica Users Group, 1997/11/24
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Also as I recall, DOF varies with subject distance. At close distances the DOF is more 50/50 in front/behind. shier@mnsinc.com - -----Original Message----- From: Art Searle <w2nra@3villagecsd.k12.ny.us> To: leica-users@mejac.palo-alto.ca.us <leica-users@mejac.palo-alto.ca.us> Date: Monday, November 24, 1997 6:20 PM Subject: Re: DOF question (was: Mistake in ...) >Alf wrote: >>Is there a changement in the general consens meanwhile? >>I learnt (long long years ago), that the DOF-limits are about 1/3 before >>the subject and 2/3 behind. So, I can't explain your -3.2 and +3.3 cm at >>f 1.4 from the 1.4/75 mm Summilux. > >That would be true for an aperture of approximately f/28. As you open up >from there the ratio is closer. At f16 it is 2/5th before, 3/5th behind the >subject. At f/8 it is 9/20th before, 11/20th behind. As you stop down the >ratio shifts the other way. At f/64 it is 3/20th before, 17/20th behind. >Without getting too technical this calculation is a function of the >_circle_of _confusion_times_lens_aperture_times_focused_distance_ in the >divisor of the two equations for depth of field. In the equation for d.o.f. >in front of the subject, it is added to the divisor. In the equation for >d.o.f. behind, it is substracted. The formula is simpler than I make it >sound. It's easy to make a Lotus spread sheet to calculate this for you. > >Art > > >