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AdrianW2
11-Jan-2013, 23:30
I canít seem to find any information on the web concerning this lens. The thing thatís really throwing me off is the fast aperture of this lens (it looks like f2.3 but it might actually read f2.8 or f2.9), and yet it came off an old 5x7 large format camera. There is no indication on the lens of the focal length.

Hereís what I know... It is a C.P. Goerz Berlin Doppel Anastigmat mounted in a Wollensak shutter. The Goerz serial number (87312) indicates that it was made around 1902, while the Kodak No. 5 Cartridge 5x7 camera that it was mounted on would have been made between 1898 and 1900. The front element of the lens is about 30mm in diameter and the inner diameter of the opening of the brass lens is about 46mm.

It would be very helpful to know what the focal length of this lens is, and also if it is rare/valuable.

ScottPhotoCo
12-Jan-2013, 01:26
Sorry that I can't help with your question, but that is one beautifully designed lens!

Tim
www.ScottPhoto.co

Steven Tribe
12-Jan-2013, 01:38
Never take the indicated F value seriously on lenses which are early!
Many scales were in use at the same period.

I don't have the conversion table in front of me (wikipedia?) but I can see US on the aperture plate.
US=uniform scale.

US F2.8 is approximately modern F6.8 which is correct for the Double anastigmat Goerz.
I believe there is an engraving with either size no. or/and focal length somewhere on this lens.
But this may have been on the discarded barrel when the 2 cells were mounted in a shutter.
The possible sizes are :

1. 15cm
2. 18cm
3. 21cm

Size 0 12cm will also just cover 5x7" at small apertures.

This is another lens which would fit this description from Goerz - Series I D Syntor - also F6.8. But it is probably the quite common (but good) series III Dagor.

jcoldslabs
12-Jan-2013, 01:38
It appears the stops are measured in the "U.S. System" which is not at all the same as the f/stop system we're used to. Have a look at this conversion chart, columns one and two:

http://www.kolstad.us/ebay/diaphragmnumbers.jpg

Your lens' marked maximum aperture of U.S. 2.3 would correspond roughly to f/6.3 or f/6.8, so the lens is likely an early Dagor. Not as fast as you thought, but a nice lens nonetheless.

Jonathan

AdrianW2
12-Jan-2013, 13:01
Your information, Steven and Johnathan, was very helpful. I determined the lens to have a focal length of 21cm by comparing the image on my 4x5 camera with that of my 210mm Sinaron S lens Ė the image is virtually identical.

There are no lens markings other than what was stated in my original posting along with a DRP patent number. But this lens does seem to match the description of the #3 (8 ľ inch) Goerz Double Anastigmat Series III lens.

If anyone knows how to verify that this is Series III rather than a 1C or 1D lens Iíd be interested to hear how to do that. I know the Series III is f/6.8 vs. the Series 1C at f/6.3, but given that the US aperture scale of my lens reads something between f/2.3-2.9 (I canít quite make out the second number) I think it could be either one of those.

Louis Pacilla
12-Jan-2013, 14:12
If anyone knows how to verify that this is Series III rather than a 1C or 1D lens Iíd be interested to hear how to do that. I know the Series III is f/6.8 vs. the Series 1C at f/6.3, but given that the US aperture scale of my lens reads something between f/2.3-2.9 (I canít quite make out the second number) I think it could be either one of those.

Hey Adrian

You can count the reflections the cells. Pretty sure it's two strong, one weak reflections per cell.

I'm also pretty sure that you have a nice early Double Anastigmat Series III.

Steven Tribe
12-Jan-2013, 14:30
The series III (DAGOR) patent no. (DRP) is 74437.


"comparing the image on my 4x5 camera with that of my 210mm Sinaron S lens Ė the image is virtually identical."
Qualitywise, as well!
Goerz gave official coverage as 24x30cm stopped down for the 210mm.

Dan Fromm
12-Jan-2013, 15:07
Two weak reflections, Louis. Each cell has two air-glass (strong reflections) and two glass-cement (weak reflections) interfaces.

Tony Evans
12-Jan-2013, 15:08
If you compare with the "3" in f 32, it does not appear to be 2.3. (round top vs flat top).

Louis Pacilla
12-Jan-2013, 17:06
Two weak reflections, Louis. Each cell has two air-glass (strong reflections) and two glass-cement (weak reflections) interfaces.


Thanks Dan! What Dan said.

AdrianW2
12-Jan-2013, 19:22
Thanks for the patent number Steven. Sure enough it does say ďDRP No 74437Ē on the brass (you can make this out in the second photo that I posted), so that confirms that it is indeed a Series III lens.

Tony, thatís a great observation regarding the font of the letter ď3Ē. Therefore the large aperture must be either US f/2.8 or f/2.9Ö both of which would roughly correspond to the f/6.8 that we are familiar with.

When I close the shutter I do see two bright reflections and two dim reflections on the front cell, and when flipped around on the rear cell also Ė eight reflections total. I can see this with a strong light facing the lens, but with the light off I only see two reflections on each cell.

Iím amazed at how well this lens has held up over the last 110 years. There is only the very faintest hint of discoloration in the cement between the elements. And looking through the lens, the glass looks crystal clear with the exception of two miniscule (pin-prick) air bubbles in the front group. Goerz must have known that we would still want to use these a century later!