My rule of thumb is that when I use a lens designed for film cameras on the *ist D, I get one stop less DOF as what is engraved on the lens. Example for a 55mm lens: DOF indicator says "infinity to 9m" for f=11. On the *ist D this will become "infinity to 12m" as indicated for f=8.
However, you get one stop more DOF than using the 'equivalent' focal length on a film camera at the same aperture. Sven Zitat von [EMAIL PROTECTED]: > > Fra: "Jens Bladt" <[EMAIL PROTECTED]> ... > > Some say, that smaller formats have greater DOF (Photonet). They say that > in > > order to get comparable images, I must use shorter focal length to go with > > the smaller format, thus achieving greater DOF. They are using circle of > > confusion (COF) theories to support their point of view. > > If you want the same field of view, that is correct. > > > I (and Photozone) say, that smaller formats only show a part of the image, > > captured by a specific focal lenght. If I shoot the same scene twice with > > the same camera, same lens (focal length( and same aperture and focus > point, > > you will get identical images on let's say APS and 35mm film - that is for > > the part, that is covered by the smaller format (e.i. APS). I say that the > > DOF of these two identical images - is exactly the same. I say that focal > > length, aperure and focal distance determins the DOF. > > If field of view is unimportant, that is correct. The APS size sensor simply > crops the image. > > > IMO COF theories are somewhat subjective, because the point to where a > point > > looks like a disc, depends on the degree of enlargement. I think that the > > smaller image, captured by a shorter focal length needs more enlargement, > > thus less appearing less sharp. > > > What is right and wrong here? > > Both, depending on you priorities. If angle of view is important you say the > first, if DOF is more important you say the latter. In addition, as you say, > the degree of enlargement also plays a part, along with > resolution/diffraction limits etc. > > This image: > http://foto.no/cgi-bin/bildekritikk/vis_bilde.cgi?id=13611 > is impossible to make with an APS size sensor, because of the combination of > shallow DOF and field of view. This was made using a 28mm @ 1:2.0. A > corresponding 18mm will not be able to make the large difference between COF > in focus and in the background. Compare images made with MF and APS formats > and this is much more evident. > > DagT > >
