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View Full Version : Goerz Rectagon 3" (75mm) F6 coverage



dogdog
31-Jul-2017, 19:24
I recently acquired this lens, and have read conflicting information. I can't find any information on its image circle, other than that an old Goerz catalog says it has a 90 degree field of view at F6 and can cover 4x5 wide open, and a regular user has stated that it has a 100 degree FOV. Neither of these statements provides the exact circle.

I was planning on using it on a 6x12cm camera, but have read that it can cover up to 5x7 inch when stopped down to F22 and above (with some corner vignetting). This would mean it could be used on a 6x17cm setup of some kind. My understanding is that 6x17 cameras require a 179mm circle.

Can anyone confirm what the exact image circle is?

Jim Jones
1-Aug-2017, 06:06
The Lens Vade Mecum says 90 degrees, although without a source citation.

jesse
1-Aug-2017, 06:57
https://farm5.staticflickr.com/4312/36176641571_faa6212d30_o.jpg

dogdog
2-Aug-2017, 08:01
The literature at pacificrimcamera.com indicates that the 90 degree figure is wide open at F6. I'm guessing that at F16 and above, that figure is probably closer to 100 degrees, and realistically, this is where the lens should be used anyway.

There's no data on image circle, though. A 179mm circle is required for 6x17, which is 30mm shorter than the 209mm minimum required for 5x7.

Given that the Field of View for 75mm on a 5x7 is 97 degrees, my guess is that the Field of View of 75mm on 6x17 is somewhat smaller, closer to the 90 figure. Stopping down the Rectagon probably brings it very close to 6x17, if not fully covering it. What is exciting about this is that the lens' compact size means it can be closed down into a folding-plate camera kind of setup.

http://www.pacificrimcamera.com/rl/00259/00259.pdf

http://lensn2shutter.com/angleofviewchart.html

dogdog
2-Aug-2017, 10:53
Does anyone know if Field of View is calculated in terms of horizontal or diagonal length? Thank you.

Dan Fromm
2-Aug-2017, 18:08
It is a circle, 150 mm in diameter. In your terms, diagonal.

dogdog
2-Aug-2017, 21:08
Thanks, Dan. I'm going to shoot the full 6x17 frame to get a 6x15 image. Cut a hair off the top and bottom, and it's the same aspect ratio as 6x17.

Mark Tweed
3-Aug-2017, 14:11
Check out this fellow's website -

https://63alfred.smugmug.com/Shootingfilm/Cameras/Goerz-Rectagon-6-x-14-Camera/

dogdog
4-Aug-2017, 09:40
Wow, 6x14 seems to be the way to go with this lens! He also had data on the film to flange distance for this lens, which is about 72mm.