Just to clarify my other post on this, a 70mm on the digital has exactly the same magnification as a 105mm on on 35mm film if the images are framed the same and printed the same size (and they would necessarily have to be taken from the same distance), and thus has no effect on the DOF. In this particular case only the difference in aperture diameter is giving the 70mm a bit more DOF.
-- graywolf http://www.graywolfphoto.com http://webpages.charter.net/graywolf "Idiot Proof" <==> "Expert Proof" ----------------------------------- Mark Roberts wrote: > John Francis wrote: > >> On Sat, Sep 16, 2006 at 01:28:26PM -0400, Mark Roberts wrote: >>> Ryan Brooks wrote: >>> >>>> Adam Maas wrote: >>>>> At f2.4, the 70 is about perfect for me. Essentially the same length and >>>>> speed as the legendary Nikon 105 f2.5, which is a superb portrait lens. >>>>> >>>> You are getting more DOF with the 70mm though. >>> Not true. Not at the same subject magnification, anyway. (And that's >>> what you'll be doing if you compare both lenses as portrait lenses.) >> Actually, Mark, Ryan is right. >> >> A portrait taken with a 105mm lens at f2.8 on a full-frame camera will >> have a shallower depth of field than the same portrait (taken from the >> same spot and enlarged to the same size) > > Right. But I specified "same subject magnification", not "taken from > the same spot". And "same subject magnification" is pretty much how > everyone does portraits: You frame as a head shot, waist-up, 3/4 or > full length and compare two lenses with this view. I've never heard > anyone saying. "Well this Lens 1 has shallower depth of field with a > head shot than Lens 2 does with a 3/4 shot": It's not a meaningful or > useful comparison. > -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
