First of all, I have not looked through every thread that has covered petzvals - there are just too many! I have rechecked with VM and read CCHarrison's excellent website article. I also know that there have been discussions of "swapped" rear elements - especialy in projection petzvals. My question is basically - "did Dallmeyer's redesign become the optical standard (with necessary small variations because of patent protection) for both later camera and projection Petzvals?". I note that CCHarrison shows a Suter from 1866 which had already adopted the Dallmeyer redesign. I have often been in doubt with projection petzvals which I have collected the last year or so (my budget doesn't stretch to the real thing) as to the correct sequence. But yesterday I received one where there could be no doubt - the inner rear lens was fixed in the barrel along with a similarly fixed spacer. It was the Dallmeyer variant. It's mounting is such that I could easily fix up a softness control - gradual turns away from the spacer ring. This is the only projection lens I have where the two lens weren't loose under the locking ring and it is f2.5 rather than the usual F.6.
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