Leonard Evens
26-Jul-2005, 13:42
I just got a Rodenstock center filter from B&H, but the various numbers on the cover of the case and on the filter housing are a bit confusing. It came without any instructions, and so far I haven't been able to locate any specifications for the filter anywhere on the web.
One label on the case it came in says "Centerfilter E 67/86 1.5 x", and it has what looks like what might be some sort of serial number---four groups of numbers separated by periods. The filter mount itself also says "E 67/86 centerfilter" but instead of "1.5 x" says "ND 0.45." There is nothing else on the mount except the Rodenstock name and "Made in Germany". Finally, there are two other labels on the case both of which say "Rodenstock 67 mm center filter 3 X F/Grandagon-N" and have some other different numbers, along with UPC codes.
I am trying to make sense of all these numbers. A density of 0.45 corresponds to 1 /1/2 stops, so if the 1.5 refers to number of stops, that might make sense. I checked the filter with my spotmeter and it does appear to reduce the light intensity at the center by about that amount or perhaps slightly more. If I interpret the 3 X to mean that the exposure has to be increased by that factor, that would correspond to a change of about 1.6 stops, which would be more or less consistent with the other interpretations.
I plan to use the center filter with a Rodenstock f/6.8 Grandagon-N and a Rodenstock f/4.5 Grandagon-N, each of which has a 67 mm filter mount. (The filter was clearly designed for those lenses.) Some calculations---or Kerry Thalmann's tables in the latest issue of View Camera Magazine---show that the fall off for the 90 mm lens with movements and the 75 mm lens without movements probably is just about 1.5 stops, and that is how I plan to use the filter.
Do I have this right, or is something else going on here?
The other interesting thing is that the filter itself appears to be about 86 mm in diameter, but the opening in the mount is 67 mm. I presume that means that in principle, the filter could be remounted in an 86 mm mount, and used that way. Is that right?
One label on the case it came in says "Centerfilter E 67/86 1.5 x", and it has what looks like what might be some sort of serial number---four groups of numbers separated by periods. The filter mount itself also says "E 67/86 centerfilter" but instead of "1.5 x" says "ND 0.45." There is nothing else on the mount except the Rodenstock name and "Made in Germany". Finally, there are two other labels on the case both of which say "Rodenstock 67 mm center filter 3 X F/Grandagon-N" and have some other different numbers, along with UPC codes.
I am trying to make sense of all these numbers. A density of 0.45 corresponds to 1 /1/2 stops, so if the 1.5 refers to number of stops, that might make sense. I checked the filter with my spotmeter and it does appear to reduce the light intensity at the center by about that amount or perhaps slightly more. If I interpret the 3 X to mean that the exposure has to be increased by that factor, that would correspond to a change of about 1.6 stops, which would be more or less consistent with the other interpretations.
I plan to use the center filter with a Rodenstock f/6.8 Grandagon-N and a Rodenstock f/4.5 Grandagon-N, each of which has a 67 mm filter mount. (The filter was clearly designed for those lenses.) Some calculations---or Kerry Thalmann's tables in the latest issue of View Camera Magazine---show that the fall off for the 90 mm lens with movements and the 75 mm lens without movements probably is just about 1.5 stops, and that is how I plan to use the filter.
Do I have this right, or is something else going on here?
The other interesting thing is that the filter itself appears to be about 86 mm in diameter, but the opening in the mount is 67 mm. I presume that means that in principle, the filter could be remounted in an 86 mm mount, and used that way. Is that right?