Goerz Berlin Trieder Binocle 7X Binoculars with Case We showed these binoculars to several local collectors and it was their opinion that these are pre-WWI. If you want to use Protars and not get burned, I think you have to buy with a return privilege.Rare Early C.P. The single elements from that one perform about the same as the other. I have a slightly longer focal length B&L protar (combined) which is acceptable but isn't astounding. Its performance as single elements behind the iris is quite acceptable to me up to 16X20 prints from 5X7 negatives. I can say I have one B&L protar which is a combined 14 and 19 inch lens which is extradordinarily sharp by even modern standards when combined. Add in the fact that the lenses within and across company lines are ageing more or less gracefully with different imperfections in the surface glass and, especially, balsam separation, and I'm not sure a one on one modern test would mean much. You don't know if the two samples you test are representative of their own product line, either. (And why would you spend your money to acquire that, these aren't inexpensive lenses.) And even that one-of-a-kind test on just two samples doesn't tell you anything you can take and then apply to different samples, since the sampling is too small. So the question is which protar is being compared across company lines? Unless some historic sample to sample test data surfaces, you'd have to find someone who happened to have exactly the same lens in both product lines. The triple convertibles, doubles, single elements with smaller diameters meant to be used behind an aperture, the f:18 wide angle series, etc., etc., etc. The variety of "protars" is considerable within company lines.
A few other thoughts.I think this question is essentially unanswerable for a number of reasons.
Considering the significance of the design the amount of information which can be found "web surfing" on this subject is minimal. Does this mean the B&L are made exactly the same way but measured differently? I don't know. The official focal lengths for the B&L's are slightly different than the Zeiss numbers, for example. Ron: I have assembled some Zeiss and B&L official data and the specs per the manufacturers do not appear to be identical.
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