[rollei_list] Re: Heliar, Sonnar, Planar [WAS Re: off topic rants]

  • From: "Richard Knoppow" <dickburk@xxxxxxxxxxxxx>
  • To: <rollei_list@xxxxxxxxxxxxx>
  • Date: Fri, 4 Dec 2009 23:55:23 -0800


----- Original Message ----- From: "Laurence Segil" <ljsegil@xxxxxxx>
To: <rollei_list@xxxxxxxxxxxxx>
Sent: Friday, December 04, 2009 12:41 PM
Subject: [rollei_list] Re: Heliar, Sonnar, Planar [WAS Re: off topic rants]


Beats me, of course, but that's why one can attribute magical properties to lenses and make them your favorites for what may only be happenstance. Currently in love with an uncoated 210mm Goerz Doeppel Anastigmat Series III f/6.8 (Dagor precursor) based on a single 8x10 image taken over the summer. But the same scene shot from the same spot with a host of different lenses (including the 300mm Heliar and a state of the current art Schneider 210mm Super Symmar XL) didn't come close to the glow of the DAIII image. Probably luck and magic, maybe change in the lighting on a partly cloudy afternoon, but I choose to credit the lens as the most readily identifiable and verifiable difference between how the different images were made. Otherwise the camera (Canham Traditional 8x10) was the same, the film type (8x10 Fuji Pro 160S) and holders were the same, all film processed at the same time by the same lab (Precision Imaging, now Phoenix Imaging, Chicago), scanned by me in the same fashion on the same scanner (Epson V750) and handled in pretty similar ways in photoshop (color inverted with CF systems ColorNeg plug-in), printed on the same paper (17x22 Ilford Gold Fiber Silk) with the same printer and ink (Epson 3800) and admired (though only by me, alas) under the same lighting conditions (my mess of a "study"). Yet there are very clear differences between the different renderings (a 19" Red Dot Artar produced the sharpest image) and I love the look of the Goerz image. So do I know it's the lens? No, but I think there's a pretty good chance it's a
contributing factor.
But it's still probably mostly magic.
Best
Larry Segil
On Fri, Dec 4, 2009 at 12:57 PM, Dennis Purdy <dlp4777@xxxxxxxxxxxxx> wrote:

The Dagor is famous for this look. At large stops the Dagor has a lot of zonal spherical aberration. Spherical affects the whole image rather than being proportional to the image angle. Its main effect is a softening of the image and a sort of glow around bright highlights. This is essentially the same aberration that special soft-focus lenses rely on. The amount in the Dagor is only moderate and disappears quickly as the lens is stopped down so that by f/16 its quite sharp. Beause the Dagor has only four glass-air surfaces its flare is low even when uncoated. Dagors also have very good color correction. When stopped down to around f/45 a Dagor will cover very nearly 90 degrees so it will work as a wide-angle lens and is especially valuable on cameras with a lot of movements. However, the same spherical aberration causes the apparent point of best focus to change as the lens is stopped down. This is known as focus shift. At large stops the lens should be focused at the stop at which its going to be used. For small stops focusing at f/16 will take it past any significant shift. The focus shift makes Dagors unsuitable for cameras with rangefinders. The names of all Goerz lenses was changed in 1904 so if you have a Goerz Dopple Anastigmat it will date from somewhere between about 1892 and 1904.

--
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx

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