Archived posting to the Leica Users Group, 2008/05/10
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Seems so obvious now that I think about it. Should've paid more attention in Geometry... Phil On May 10, 2008, at 11:22 AM, Jeff Moore wrote: > 2008-05-08-13:48:57 Jim Nichols: >> I agree with Gene. If a lens will cover 36mm in width, it will >> cover the >> same dimension in height. Hence, it should cover at least 36x36mm. > > Er, what part of the Pythagorean theorem is confusing here? Don't > just > count on words which sound nice together; draw the two formats packed > into circles, with the enclosing circles just kissing the corners of > the > enclosed rectangle (which might be a square). If an image circle is > to > be guaranteed to cover a rectangular format, the circle's diameter > must > be greater than or equal to the format's diagonal. The format's > diagonal > is the square root of the squares of the sides. > > http://en.wikipedia.org/wiki/Pythagorean_theorem > > For 24x36mm, that's 43.3mm (hence the Leica MTF graphs which go from > zero to 21.6mm, half that -- the radius from center to edge of the > image > circle which covers 24x36). > > For 36x36mm that's 50.9mm. > > 50.9 is bigger than 43.3. > > Sure, some current R lenses (especially the longer ones) may have > coverage to spare, but more coverage *would* be required. > > -Jeff > > _______________________________________________ > Leica Users Group. > See http://leica-users.org/mailman/listinfo/lug for more information