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90mm f/6.8 Optar Film to Flange Distance

 
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VTHokiEE



Joined: 30 Jan 2017
Posts: 13
Location: FL

PostPosted: Sat Mar 18, 2017 12:29 am    Post subject: 90mm f/6.8 Optar Film to Flange Distance Reply with quote

I was wondering if anyone knew the film to flange distance for the 90mm f6.8 Optar. I've scoured the web but so far I haven't been able to find out. I was planning on using this lens for a project with the lens focus fixed at infinity.

Thanks!
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Dan Fromm



Joined: 14 May 2001
Posts: 1982
Location: New Jersey

PostPosted: Sat Mar 18, 2017 1:01 pm    Post subject: Reply with quote

As far as I know Wollensak didn't publish flange-focal distances for their wide angle lenses.

Resist the temptation to build to published flange-focal distances. Lenses as made don't conform perfectly, or even well enough, to them. You're going to have to get the lens you'll use and measure its flange-focal distance. Then build the camera.

Zeiss worked to high standards. This isn't enough. I once bought a heap of AGI F.135 aerial cameras. Each held two 38/4.5 Biogons as were sold in Hasselblad SWCs. The F.135 is fixed focus and the camera body is precisely machined. Before mounting a lens, AGI measured its focal length and FFD, marked both on the lens' barrel and made a shim, marked with its thickness and the serial number of the lens it was for, to collimate the lens to the cameras.

I ended up with 20 Biogons. Focal lengths ranged from 38.3 mm to 38.8 mm. FFDs weren't of much interest to me but they varied too.
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VTHokiEE



Joined: 30 Jan 2017
Posts: 13
Location: FL

PostPosted: Sat Mar 18, 2017 1:14 pm    Post subject: Reply with quote

Thanks for the help and advice. I'll simply measure it then, I plan on using it stopped down so hopefully that accounts for any mistakes in my measurements.
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