Archived posting to the Leica Users Group, 2001/02/09
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]http://www.ida.liu.se/~marho/dof/dof.html **********quote from above article*********** The presence of aberrations, especially spherical, does increase depth of focus, and hence depth of field as well. The reason is that the rays from the rim of the aperture of a spherically aberrant lens come to a focus at a different distance from the lens than rays from the center, so that there will be an image of sorts all the way from the marginal focus to the axial focus, although at no point will the image be clean and sharp. Incidentally, this explains why simple lenses can be used on box cameras with no focusing mechanisms; a well corrected could not be used this way because it would have too little depth of focus. ******end quote**************** I think this is the best explanation for why the newest lenses and films seem to not work well using old values for DOF. Its why when you follow the marks on the lens for DOF at a given aperture and distance they might not suffice. The easy answer is use one stop more than indicated. I'm happy to have lenses that good. Henry