On Wed, 26 Feb 2003, Fred wrote: > > Is a 50mm a real 50mm on this new Pentax? > > No. Because the sensor is not a 36mm x 24mm sensor, but is smaller, > the "multiplier effect" applies.
It's a bit more complicated than this. A lens with a focal length of 50mm has the same perspective and DOF regardless of the size of the sensor or film. What seem like differences in focal length are really just differences in cropping, which is a different beast altogether. If you put a 50mm lens on a DSLR and compare it to one on a 35mm film camera, both will give you the same DOF. The apparent focal length will be different, with the DSLR enlarging the subject roughly as much as, say, a 35mm lens with a focal length of 75mm would. But you would get exactly the same effect if you cropped out a part of your 35mm negative and enlarged it, so all the DSLR is really doing is cropping your 50mm shots enough that they look like they were taken with a 75mm lens. 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. HTH, chris
