Lancaster Rapid Rectigraph - unknown aperture scale

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Matthijs

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Jun 2, 2004
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Groningen, N
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Hi all. I've recently purchased a nice looking Lancaster & Sons Rapid Rectigraph 1/2 plate lens. The aperture ring is marked 10 wide open and then closes down by 20, 30, 40 and 50. There is a parallel marking named 'time', starting with 1 (at marking 10) and decreasing in steps of 2, 4, 8, 16, etc.

I've found the conversion table at largeformatphotography.info (here) and I suspect that my lens has the Dallmeyer aperture scale. However, I found (there was a url link here which no longer exists) by Ole, who owns a lens from the same maker, and has determined that it's an actual f/stop scale.

So, which one is it, the Dallmeyer scale or the 'normal' f/stop scale? Before I start measuring and doing math, I hope someone can just give me the answer :wink:
 

Ole

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I always suspect any old aperture scale to be marked in AN, unless I can prove otherwise.

AN seems to have been one of the most popular scales in Britain for quite a long period - it's my abbreviation for "Arbitrary Numbers".
 
Joined
Jul 17, 2006
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Measure the size and focal length and work out the ratio. Mine is surprisingly apparently a real f stop scale with similar markings, though it may just be that the ANs happen to be close enough.
 
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