Archived posting to the Leica Users Group, 1999/07/09
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]None of my (or any one else's) DOF charts and/or computer DOF programs have a parameter for lens design, lens manufacturer, aberrations, or any thing other than the focal length, at what distance focused, and the f/stop. So you may be correct, but it is not a parameter that photographers think about or have to deal with. The fringes of any DOF area is marginal anyway. I doubt that a lens artifact is going to push things way out to the point that the focal length DOF charts should be considered incorrect. The single variable that a photographer has to think about is... what is my acceptable circle of confusion. From that, the focal length, the focus distance or magnification, and the f/stop, useful DOF can be computed. Now if the lens is just plain crappy, none of this is relevant. Nothing is really in focus. It is at the fringes all of the time. DOF goes from crappy to really crappy. Get another lens. Or use it for Bokeh only photographs. Jim At 09:19 PM 7/9/99 +0200, you wrote: >I have to disagree. The greater the spherical or chromatic aberration, >the larger the acceptable coc, so a greater percieved DOF. Since Leica >glass is well corrected in these aspects, it is nothing to worry about. >/Peter > >Jim Brick wrote: >> >> Every lens, except some zooms and I think the Tri-Elmar, has DOF info, for >> that lens, engraved on the lens itself. The instruction booklet or most >> photo texts also tell how to read this engraved scale. Aberrations aren't >> involved. Lenses of the same focal length and at the same f/stop, at the >> same distance, have the same DOF. >> >> Jim >> >> At 10:11 AM 7/9/99 -0700, you wrote: >> >Mikiro Mori wrote: >> >><snip> >> >> I am beginning to understand better....@@; >> >> So, DOF is calculated on the assumption that the lens has no abberations. >> >> That's why we sometimes feel that lenses with the same focal length and f >> >> stop (but with different abberations) give apparently different DOFs. >> >> >> >> Mikiro >> >