Archived posting to the Leica Users Group, 2004/02/16
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Tim Atherton wrote: >>What happens is that that when you mount your 50 mm lens on a camera >>with a 1.5 multiplication factor, the 50 gives you the magnification and >>field of view of a 75mm lens - BUT - it still has the depth of field of >>a 50 mm lens because you are still using the central portion of the 50 >>mm lens...or something like that. ;-) >> >> > >i.e there isn't a change in depth of field? > > No there isn't. >this is where I get confused with LF lenses - and the principle is the same. > >Using the same lens with different formats (8x10 to 4x5 or 35mm to >chip/sensor) doesn't change the depth of field does it? My 250mm lens is a >moderate wide angle on 8x10, but telephoto on 4x5. But the depth of field >hasn't changed if I go from the 8x10 back to the 4x5 back - or has it? > > Correct. For example suppose your 250mm lens when focussed slightly short of a bright 1mm ball, casts a "circle of confusion" on the film of roughly 3mm (i.e. it is slightly out of focus). Regardless of the size of the film, the circle will be 3mm. The lens has no way to "know" what kind of film or digital sensor is sitting behind it. It just focusses the image on the plane of focus. Jonathan - -- To unsubscribe, see http://mejac.palo-alto.ca.us/leica-users/unsub.html