View Full Version : Datapoint: pre-Dagor 7" Series III coverage

john wilton
9-Jun-2008, 15:42
Looking for an 8x10 wide angle that would be brighter (easier to compose and focus in the dark woods) than my Wollensak Series IIIa f12.5, I picked up a nice 'Goerz Double Anastigmat US Pat. 528155 Series III No. 2 Focus 7" No.70258', presumably from 1902. According to 1913 Goerz PR, it should cover sharply 5x7 wide open, and 8x10 at f32. In this case, at f45 this sample is about 1/2" (radial) short of reaching the corners...darkening at 1/2" from corner and clear film in extreme corner. Acceptably sharp in corners, however.

The lens came in a working Ilex General shutter. When considering buying the lens I could see the aperture scale was factory stamped to 6.8, so I thought that even though it was hand-inscribed with 5.6 and 4.5 there was a good chance that the shutter was right for the lens. However, it was immediately obvious that the stamped apertures were way off; I recalibrated by scaling down from my 9.5" Dagor. I took a comparison shot with the Wollensak and the Series III. Wondering if spacing might be off; I shot a second time with the front cell unscrewed half a turn and refocusing. Scanning a tiny fragment of the image at 3200dpi on a V700, it seems the unscrewed shot is marginally sharper. The limiting factor seems to be the film grain (Arista 100). Both are noticeably sharper and more contrasty than the Wollensak. (I don't mean to slight the Wollensak, it is very sharp and covers corner to corner.) There is the ever-present risk of operator error so more tests needed, or maybe not...resolution is far beyond what I need for a 24x30 print.

Of course I should just use and enjoy the lens, but any comments, advice on test methodology etc appreciated.

Dan Fromm
9-Jun-2008, 16:09
Funny you should be surprised that a 7" Dagor won't cover 8x10. The question of 7" Dagors' coverage was beaten deep into the ground in this thread: http://www.largeformatphotography.info/forum/showthread.php?t=13109&highlight=lousy+dagor

Please take the time to read all of it, it just gets funnier and funnier.



john wilton
10-Jun-2008, 12:43
Dan, scary and sobering.

Does anyone have a lens like mine in its correct barrel or shutter and could caliper-measure overall length, or micrometer-measure the seat thickness of the barrel/shutter? I see mine has a wire shim around the rear cell's threads, which may or may not be a good sign.