You know the dimensions of the sensor, you can put up a tape measure on a wall and take a picture at a fixed distance (to the focal plane), see what the magnification ratio is by looking at the picture and seeing what the resultant height of the image is, use the ratio to compute your focal length.
[EMAIL PROTECTED] wrote: > How is one able to tell what the exact focal length of a given lens is? > Or, more precisely, how do we, without appropriate testing equipment, make > that determination? > > As an aside, Leica marks the exact focal length of some of their lenses on > the lens barrel. Even though the lenses are "the same," there are still > focal length variations. So, even if we can accurately determine the focal > length of a given lens, it may be that the focal length of another sample > is different. > > Shel > > > > >>[Original Message] >>From: Kostas Kavoussanakis > > >>I think the K18 is also more of a 19; I seem to >>have read this on the list at some point. > > > > -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
