12" Goerz?

[Matt_1193]

I just picked up a 12" Goerz lens in an Ilex #3Acme and I am having a heck of a time identifying the exact model. Here is the exact stamping - "C. P. Goerz Am. Opt. Co. Apochromat Artar 12in F:9 No.768079". The serial numb er is repeated on the rear elements. I cannot find this f-length/aperture combo listed in any resource that I know of . All of the Apo Artar Goerz I can find are "Red Dots" - but this lens has no dot or text indicating such - The Dagors are all f/6.8 not f/9. Any of you lens gurus/historians out there have a clue about the identity of the old boy?

[neil poulsen]

I believe it's the same formula as the Red Dot Arters, but an earlier version. Some people have suggested that the red dot on the lens was more hype than anything. Is the lens coated? The red dot Arters are f9 lenses, except for the higher focal lengths.

Kingslake said of this lens, " . . . a basic dialyte design in which the positive elements were of dense barium crown and the negative elements were made of telescope flint glass having a favroable partial dispersion, so that the secondary spectrum could indeed be reduced. This lense remained the regular Goerz process lens for some seventy years."

[Kerry L. Thalmann]

It's a pre Red Dot APO Artar. According to the serial number, it was made in ab out 1946 or 1947. The first Red Dot Artar was serial number 779612 made in Octo ber, 1953. Your lens is probably uncoated (I believe Goerz started coating thei r lenses around serial number 770000). The design is the same as the later Red Dot APO Artars (4 elements in 4 groups). If is is uncoated, it will be lower in contrast and more flare prone than a coated sample, but should otherwise be sim ilar in performance.

Kerry

[Matt_1193]

Neil, It does not appear to be coated (maybe single?). I took it apart for cleaning - the construction seems to be one frontal element air-spaced from one at the rear (two cemented?). This is true at both front and rear groups.

[Matt_1193]

Thanks Kerry. Any guesses on coverage, guys? I find that the Red Dot 270mm has an image circle of 231mm, while the 305mm Dagor is 431! I'm guessing this might be somewhere between -

[Kerry L. Thalmann]

Matt,

I don't have the official Goerz specs handy for this lens, but Artars were gener ally listed as having coverage of 46 or 47 degrees. That would yield an image c ircle in the 260mm range (at infinity) for the 12" Artar. The circle of illumin ation for an Artar will be larger than the circle of good definition. These len ses did not use mechanical vignetting (field stops) to limit the circle. What t his means is you will get a much bigger cricle of light, but it will start to ge t progressively softer as you move beyond 46 degrees. Unlike the Dagor, the ima ge circle of the Artar does not increase substantially as you stop down. It's p retty much 46 degrees from wide open down to f64. For close-up work, the 12" Ar tar would be useable on 8x10 (or even 11x14) at 1:1. For infinity use, 5x7 is p retty much the limit (if you want sharpness corner-to-corner).

Kerry

[e]

I have an old uncoated 12" Goerz that covers my 12x20 straight on.

[e]

12" Goerz dagor that is.

[Jeff Scott]

I have some literature form C.P. Goerz American Optical Company from 1960 that lists the 12" Red Dot Artar as covering 6 1/2" x 8 1/2" film size. Just for kicks the list price with the #3 Acme shutter was $325.00.

[David A. Goldfarb]

The Artars were designed for copy work, so big coverage at infinity wasn't important. More coverage would have meant more stray light bouncing around inside the camera, and would have reduced contrast.