View Full Version : Interchangeability of Zeiss and B&L Series VII Protar cells?

John Schneider
4-Jul-2013, 09:52
Interchangeability of Zeiss and B&L Series VII Protar cells?

Notwithstanding that one is probably Metric threaded and the other English, were they made such that they would be correctly positioned w.r.t. the aperture and the other cell if the threads were compatible? I have some of each (including some of the later Zeiss ones that were coated), and it would be nice to be able to use them together, even if it meant rethreading or making adapters for the cells of one manufacturer.

Steven Tribe
5-Jul-2013, 00:51
Interesting question.
I have the feeling that neither B&L and Zeiss changed the optic design during the very long period of time these were made.
They were far too busy with other products.
I would guess that, apart from the question of threads, any mixture of series VII cells from Zeiss, B&L, Ross, Krauss and all the others, will perform well as a VIIa.
The usual reason given for Zeiss' many licences to others is that they had limited own production facilities in the early/middle 1890's. This may not have applied to lens grinding etc. so it is possible that they supplied the glass to, for instance, Ross who were then responsible for the brasswork.
MW in London certainly had (has had) a "manufacturer mixture" series VII for sale for a long time

5-Jul-2013, 08:49
Real double anastigmat cells (like the VII Protars) should work together just fine not only regardless of the manufacturer but even regardless of the exact type. I've combined a half of a 6.8/135 Goerz Berlin Dagor with a half of a 6.8/135 4/4 double Gauss type Doppel-Anastigmat Hekla by Huttig one day, and the resulting lens was perfectly sharp, and had all its residual aberration somewhat in midway between the original Hekla (a really sharp lens btw covering 5x8" stopped down, but very low in contrast without coating and alas also really bad in its out of focus rendition) and the original Dagor.


Not all the old pieces of glass marked "Doppel-Anastigmat" were actually double anastigmats. The "Doppel" tag was a great sales driver those days (in a number of different books of the era one can easily find words like "dear amateurs, contrary to the popular belief, the 'double anastigmat' label does not actually mean the lens is twice as good as an ordinary anastigmat..."), and I've seen lots of celor-type and some other lenses marked as double anastigmats - though they actually aren't at all.

And a lot of the later post-WWII convertible lenses are not the classical double anastigmats either. Mixing halves of a f/5.6 convertible Symmar and a convertible Sironar do not result in a decent lens at all. And neither do these halves work if combined with a Dagor's or any other old-type double anastigmat's halves.