On Tue, Apr 07, 2009 at 09:32:47AM -0300, Luiz Felipe wrote: > You're actually saying if one zoom out (reduce the magnification of the > subject) and crop back to the desired composition the DOF will be > increased, right? So the pic taken with the zoom at 35mm will present > greater DOF than the one taken at 70mm, after you enlarge both to the > same subject size, right?
This is the premise behind point and shoots having greater depth of field than APS which has greater depth of field than Full Format. Or conversely if you want to limit DOF at a particular angle of view, you may need to go to FF. > > ...so the K20d has greater DOF than the *ist DS, right? Because you can shoot with a shorter lens and crop, since DOF is based on focal length squared and CoC as a linear value. Mind you, if you down res a photo from 2000x3000 pixels to 400x600 then an edge that had been 5 pixels wide is now only 1 pixel wide so even if DoF can't be changed in post processing, there will be a lot more lattitude in what you cannot see is out of focus. > > I love numbers... :-) > > LF > > JC OConnell escreveu: > >depth of field is determined solely by in camera magnification > >and working fstop. So cropping/format is not a factor but changing > >lenses from a given distance will affect DOF, likewise moving further > >away with the same lens and stopping down more will also both increase > >DOF. > > > >JC O'Connell > >hifis...@gate.net > > > > > > > >-----Original Message----- > >From: pdml-boun...@pdml.net [mailto:pdml-boun...@pdml.net] On Behalf Of > >Larry Colen > >Sent: Monday, April 06, 2009 4:35 PM > >To: Pentax-Discuss Mail List > >Subject: Trading resolution for depth of field > > > > > >Perhaps someone has already done the math, or the experimentation, and > >can just give me the answers. > > > >Scott's pictures of his Nishiki inspired me to shoot some of my mongrel > >legnano. I rode it to lunch today, and on the way back to the office was > >getting some shots of it with some lupin by the side of the trail. > > > >I didn't have quite as much depth of field as I'd like, so I decided to > >try zooming way out and then just cropping. Smaller sensor, shorter > >lens, more depth of field. If the equation is linear, I should get the > >same DOF by downresing (downrezzing?) a longer lens over the whole > >sensor, as I would using a shorter lens and cropping. > > > >This would also mean that a K20 would have a lot less DOF than my K100 > >at the same focal length, assuming that they were blown up large enough > >that the sensor resolution became a factor. > > > >So, if I'm willing to trade resolution for depth of field, am I better > >off using a wider angle lens and cropping (my intuition says yes), or do > >I get the same benefit by just combining pixels (which would also reduce > >noise) for a larger circle of confusion? > > > > > > -- > Luiz Felipe > luiz.felipe at techmit.com.br > http://techmit.com.br/luizfelipe/ > > -- > 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. -- The fastest way to get your question answered on the net is to post the wrong answer. Larry Colen l...@red4est.com http://www.red4est.com/lrc -- 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.
