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- Mar 23, 2005
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Dante, you don't need to be told what to do. I've occasionally had spells of focusing and general blurriness problems, have responded by testing carefully with everything locked down tight and varying possible causes one at a time. The diagnosis has always been the same. Operator error, not equipment problems. That said, if you can't solve it yourself the likely thing to do is to have the lens checked properly.
Rodenstock says explicitly somewhere or other that their CFs contain two pieces of glass of the same RI and dispersion, one with a neutral colorant. The dark piece's curvature is calculated to give the necessary density where needed, the clear piece fits the dark one. The VM says that R'stock first made center filters this way before WW I.
I've seen center filters for Metrogons that were a pattern of metallic dots on a piece of flat glass, denser towards the center than at the edges. So that approach is known and works well enough. I've always thought that Schneider's CFs were made like R'stock's.
Rodenstock says explicitly somewhere or other that their CFs contain two pieces of glass of the same RI and dispersion, one with a neutral colorant. The dark piece's curvature is calculated to give the necessary density where needed, the clear piece fits the dark one. The VM says that R'stock first made center filters this way before WW I.
I've seen center filters for Metrogons that were a pattern of metallic dots on a piece of flat glass, denser towards the center than at the edges. So that approach is known and works well enough. I've always thought that Schneider's CFs were made like R'stock's.