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View Full Version : Rodenstock 270mm APO Gerogon S on 7x17?



JasonC
21-Jun-2006, 06:22
Anyone tried using one on 7x17? I know Jim used the non "S" version on 11x14 and it just covered. How about the "S" version? It should have more coverage. Thanks.

Jason.

Bob Salomon
21-Jun-2006, 07:41
At 1:1 the 270 Apo Geragon covers 18 x 22" The S version covers 20x24"

the 270 has an effective focal length of 267.3mm and the S is 271.5mm.

The diagonal of a 7x17 is 18.4"
The diagonal of an 18x22 is 22" that is what the 270 covers at 1:1. At infinity it would be about half that or 11"

the diagonal of 20x24 is 24" At infinity the S would cover about a 12"

Neither will fully cover at infinity. The 270 was designed for a reproduction ratio of between 1:5 to 5:1 and optimal performance is at 1:1.
The S was made for 1:3 to 3:1 and optimal performance is also at 1:1.

Both lenses were designed so that optimal aperture is f22.

Kerry L. Thalmann
21-Jun-2006, 08:27
The diagonal of an 18x22 is 22"

the diagonal of 20x24 is 24"

Bob,

I don't dispute the rest of your comments as I have no experience with these lenses. However, the correct diagonal of 18x22 is 28.4" and the diagonal of 20x24 is 31.2", both substantially larger than the numbers you stated.

Also, rather than list what size films these lenses cover at 1:1, perhaps you could provide the angular coverage. While 18x22 and 20x24 may be the largest film sizes covered by these lenses (at 1:1), generally the coverage does not stop instantly once it hits the diagonal of those formats. With the angular coverage it would be possible to calculate the coverage at any magnification.

Kerry

Oren Grad
21-Jun-2006, 08:49
Kerry, the 270 Apo-Gerogon is specified to cover 70 degrees at f/22 and the 270 Apo-Gerogon-S is specified to cover 75 degrees.

JasonC
21-Jun-2006, 08:55
I guess now the question is will the coverage continue to increase when stopped past f22.

Jason.

Kerry L. Thalmann
21-Jun-2006, 09:05
Kerry, the 270 Apo-Gerogon is specified to cover 70 degrees at f/22 and the 270 Apo-Gerogon-S is specified to cover 75 degrees.

That equates to image circles of 378mm and 414mm respectively - not enough for 7x17 unless...


I guess now the question is will the coverage continue to increase when stopped past f22.

Can't help you with that one, but you may be better off with a 270mm G Claron. It's coverage does continue to increase as you stop down and it fits in a standard Copal No. 1 shutter.


Kerry

Bob Salomon
21-Jun-2006, 09:09
The Apo Geragon was made in 150 to 360mm focal lengths. There were 6 lenses. The only reference to coverage angle states "The six element Apo Geragon covers between 70 and 78". The literature does not state which focal length covers which angle

The S covers 75.

Apparently my calculator's memory function is flakey. Probably time to replace it but it's conversion function has worked well for the past 30 years and it was a $10.00 unit back then.

Sorry about that.

JasonC
21-Jun-2006, 09:10
Thanks Kerry. You don't happen to still have some 270mm G Clarons left over, do you?

Jason.

Oren Grad
21-Jun-2006, 09:27
The Apo Geragon was made in 150 to 360mm focal lengths. There were 6 lenses. The only reference to coverage angle states "The six element Apo Geragon covers between 70 and 78". The literature does not state which focal length covers which angle


Bob, I guess there's conflicting information about that. I have a scan of a Rodenstock product literature page with a detailed specifications table that shows all six of the Apo-Gerogons as covering 70 degrees at f/22. And I have a different one, which is just a small block of descriptive text, that mentions "covers between 70 degrees and 78 degrees".

Bob Salomon
21-Jun-2006, 09:54
Oren,

My figures are from the 1995 complete brochure that is part of a distributor catalog on Rodenstock Precision Optical given to distributors at the 1996 Photokina.

I also see a 70 reference only in a 1978 brochure.

I try to only use the data from the latest brochures we may have.

Oren Grad
21-Jun-2006, 10:20
Bob - OK, I'd guess that the detailed specification sheet I have for the Apo-Gerogons dates from the mid to late 1970's.