Goertz Double-Anastigmat verses Goertz Dagor

[Greg]

Could someone please tell me the difference between a Goertz Double-Anastigmat and a Goertz Dagor? Have owned samples of both nomenclatures and honestly have not been able to tell the difference between them using B&W film.

thanks in advance

[Dan Fromm]

Well, Goerz Ser. III double anastigmats (original name) are early Dagors (later name). Same design, different name. Dagor types, six elements in two groups. Two strong and two weak reflections from each cell, and the weak reflections can be hard to see. Earliest ones f/7.7, later f/7.7 and f/6.8

Other Goerz double anastigmats are dialyte types. Celor, Dogmar, Syntor, Tenastigmat, no name but double anastigmat and all in a variety of speeds including f/6.8. All four elements in four groups, four strong and no weak reflections from each cell.

[Jim Noel]

Dagor is acronym for Double Anastigmat Goerz. I have several of both nomenclatures,both late double anastigmats and early Dagors. I see absolutely no difference them visually or the negatives they roduce.

[Mark Sawyer]

The difference I noticed when I was using Dagors quite a bit was that the early versions lost resolution near the edge of the image circle. Later versions were quite sharp all the way out. Also, the earlier Dagors had just a touch of spherical aberration, that "Dagor glow" that also caused a small focus shift when stopping down. That seems to have been corrected in later Dagors. (I wonder if the Dagor was corrected with the new glasses that were coming out? Or just tweaked in some other way?) And of course, the coated ones had a bit more contrast, although having only two inner air-glass surfaces, the uncoated Dagors were had more contrast than most uncoated lenses.