A Dagor Dilemma!

[John Kasaian]

I am under the impression that a series lll Dagor is the "standard" field while the series lV is the "wide" field. Now I've recently come across a series ll. Series ll? Whats a series ll? Whats the difference is between a series ll Dagor and the series lll and lV? Can anyone offer any insight regarding the series ll? Thanks much!

[Bob Fowler]

Get a copy of "a lens collector's vade mecum" by M. Wilkinson and C. Glanfield (available at http://members.aol.com/oct0969/sell.htm). There is a huge section on the Goerz lenses - far too much to quote here.

To answer your question...

From the vade mecum...

Doppel Anastigmat (Layout Goe010)
Series 11a f5.5/f5.6 This was a 5+5 glass anastigmat, with single components fully corrected for use at f11. It dated 1895 or 1897, and sold from 1897, and it was patented by von Hoegh as Brit. Pat. 2854/1899. It
was usually sold as the Satz (ie Set) Anastigmat, as the Dagor was not sold this way (Lummer, p77). It does seem overcomplex but the design was defended by Goerz and von Hoegh as good as the positive glasses were set into the hollows in the negatives, helping the centering, which must otherwise have been a production problem. This is a scarce lens in the UK, probably due to its original price. By 1901 it was no longer advertised.

Series II This was the same as Series II but with two cells of the same focus, working at f5.5. The glasses are (from the front outer glass) 1.61; 1.54; 1.52; 1.61; 1.51. The correction procedure is discussed by Lummer- basically the surfaces are used one by one for the different aberrations.

Clear as mud, isn't it? The whole Goerz article by itself is worth the price of the CD.

[Ernest Purdum]

Another excellent source, easier to use than the Vade Mecum, is Rudolph Kingslake's "A History of the Photographic Lens". It's out of print, but shows up on eBay and elsewhere occasionally.

[John Kasaian]

I've got Kingslake's book---excellent! But he doesn't delve into the differences between series of Dagors.