Archived posting to the Leica Users Group, 1999/09/15
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]Frank Filippone wrote: > Marc... what is the equation for light fall off in the Hologon and > Heliar? > Is it the secon/third/fourth power? In Fstops works as well.....DItto > the > super wide angle view camera lenses.... I just forget the name....Super > Angulon? For a simple lens, the light fall off is a function of the cosine of the angle of incidence (the angle off the lens axis) to the 4th power. The so called 'cos 4th' law. I know Schneider lists a graduated centre spot ND for the 90mm Super Angulon XL (see http://www.schneideroptics.com/large/super_angulon/super.htm). I keep meaning to order one for mine. David Morton dmorton@journalist.co.uk