The optimum aperture does make a noticeable difference in sharpness with most good glass, but using it shouldn't overrule your DOF needs. With the K-5, you can set your program mode to choose the MTF aperture when you push the green button. On the new DA* zooms, it comes early -- f4 in many cases. It varies on individual lenses with focal length, and program mode recognizes that. In my experience the optimum ap on most older Pentax glass is more typically f8 or even f11. Counting on DOF to achieve sharpness is just wrongheaded in most cases. (Shooting from the hip at hyper focal distance would be an exception.). But by and large focus has to be accurate and DOF optimum for the job. Small aps, in the f16 and smaller range do cause loss of sharpness due to diffraction, but when you need a small ap for extreme DOF, you have to bite the bullet and go for it. Or shoot off a tripod with different focus points and composite the result.
On Jun 4, 2012, at 6:22 PM, Larry Colen wrote: > I was thinking about my quest for sharpness, and was considering trying to do > some research into what the aperture "sweet spot" is for each lens, and was > wondering if anyone had already made a chart of them. > > Then I wondered how much it really matters. I've heard "a couple of stops > down from wide open", "anywhere between f/8 and f/16", and a couple other > rules of thumb. I do know that on some lenses, particularly the FA50/1.4, > that stopping it down a couple of stops from wide open, makes a huge > difference. And I suspect that if you look on an MTF chart, you might be > able to easily see the difference between f/4 and f/8, but is there a > practical noticeable difference? > > There is also the question of sharpness at the critical focus distance, and > overall sharpness. That a lens might be sharper at f/4 than f/16 at the > focal distance, but with a lot more depth of field, more of the photo will be > sharper at f/16, than at f/64. > > I'm primarily interested in answers based on personal, practical experience, > rather than theory. My hunch is that as long as I'm not too close to wide > open, or pushing diffraction limits, optimizing aperture for sharpness is not > the most productive place to spend my time and energy. That I'm generally > best optimizing the aperture for the picture, and not trying to optimize the > aperture for MTF. > > -- > Larry Colen l...@red4est.com sent from i4est > > > > > > -- > PDML Pentax-Discuss Mail List > PDML@pdml.net > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and follow > the directions. -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
