On Thu, 27 Feb 2003, Maciej Marchlewski wrote: > Dnia 26-02-2003 o godz. 23:15 Chris Brogden napisal: > > > The myth about digital offering more DOF is partly true, > though. To get a > > DSLR lens that magnifies things as much as a 50mm lens for a > 35mm film > > camera does, you'll need to go with a DSLR lens with a focal > length of > > roughly 35mm (assuming a 1.5x conversion factor). When a > subject looks > > the same size through a 35mm lens and a 50mm lens, the shot > taken with the > > 35mm lens will have more DOF than that taken with the 50mm > lens. > > AFAIK if your subject is of the same size the DOF is exactly the same > regardles of focal length used.
Not true. Using a film camera, take a picture of a person with a telephoto lens so that all you can see is their head and shoulders. Then put a wide angle lens on, and walk closer to the subject until you can see just their head and shoulders. Now your subject is the same size as it was with the telephoto lens, but you have much more DOF. If you stand in one spot and use different focal lengths, the DOF and perspective will remain the same (you're basically just cropping), but the subject size will change. If you change your position so that the subject size remains constant with different focal lengths, the DOF and perspective will change. > In DSLR we have a bit different case - the subject is not projected on > media as the same size - it is smaller in APS DSLR and than magnified > so it seems as it uses the same part of the frame as in regular SLR. > So here we have a case od the same subject distance giving as the same > frame with different focal lengths. And this results in greater DOF on > APS DSLR. I'm a bit confused by your wording here, but I think I agree. :) chris
