DOF is a function of reproduction ratio. All that matters is the comparative size from the subject to the resultant print, not the focal length or the lens extension or anything else. Most DOF tables assume a print size of 8" x 10". What will differ from one focal length to another is the appearance of the image beyond the DOF. In my experience a long lens gives a better appearence of sharpness just beyond the DOF but falls apart abruptly further away from the DOF so that the subject's form is completely indistinct. OTOH a short lens gives a better account of the subject matter in the grossly unfocussed areas, but lack of focus is more apparent just outside the DOF (of course if the lens is short enough ~everything~ will fall within the DOF and the subject becomes moot). I suspect that the differences are due to the change in perspective from the close short lens photo to the more distant long lens photo, and are most likely a completely subjective perception.
Regards, Anthony Farr ----- Original Message ----- From: "T Rittenhouse" <[EMAIL PROTECTED]> > Since close up lens shorten the focal length of the lens, I would think the > DOF would be greater than with ext. tubes. > > BTW, I just got a 0.5 diopter CU to use with my 80-200/2.8 zoom. It allows > it to focus as close as 3' instead of 6'. I can't wait to try it out. > > Ciao, > Graywolf - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
