Archived posting to the Leica Users Group, 1999/09/14
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]At 11:42 AM 9/15/99 +1000, Rob Studdert wrote: > >When the gradation filter is placed on the Hologon the actual aperture is still >f8, but the effective aperture becomes f16 due to the light loss incurred by >the filter. Closing down the Heliar to f16 (to equal the effective aperture of the >Hologon) will lead to a loss of quality due to diffraction, therefore it becomes >an invalid comparison. > >Rob Studdert This is indeed true. The Large Format world has dealt with "center" filters for decades. These filters are v-e-r-y expensive! I have one for my 75mm f/4.5 Rodenstock Grandagon. This lens without the filter has enormous falloff. But in many cases, this is desirable. One of my greatest photographs was taken with this lens, sans center filter. This photograph has sold more than any of my other photographs. Cala Lilies and an old broken down fence. Ted... think of it as "peeling paint"... :-) . Anyway, center filters are generally two stops and, of course, as Rob said, it's the filter, not the diaphragm, that cuts the exposure. A fare comparison would be with both apertures set the same. To be really fare, the Heliar should have a center filter as well. I personally think that I would use the lens without center filter more than with. Just my point of view. Jim PS... Welcome back Godfrey... :-)