| Author | Thread |
|
|
10/03/2006 12:10:04 PM · #26 |
Originally posted by rami:
what i don't understand is how they acheived an F/4 ????
isnt F-stop = focal-length/aperture diameter ?
that results in an aperture diameter of what ... 420 mm ?? |
My BPOG (big piece of glass) has an OD of 18 inches and is 38 inches in length. The focal plane is about 10 inches from the rear element. The original film format used a 12" X 12" negative. Production cost was $112,000; made on contract to the US Government by Perkin-Elmer for the U2 reconnaisance aircraft. This one never flew because the program was cancelled. 28 of this model were made and most were scrapped to be purchased by astronomy nuts like me for a paltry $250. I bought mine in 1996 from a dealer that got it from the Kirtland AFB salvage sale in Albuquerque, NM. In retrospect, this was not a wise purchase as the lens is very difficult to use! |
|
|
|
10/03/2006 12:13:46 PM · #27 |
Originally posted by ElGordo:
... In retrospect, this was not a wise purchase as the lens is very difficult to use! |
Sounds like you need to treat it like an astronomy telescope and mount it on a swivel base with a platform you can move (wheels). |
|
Home -
Challenges -
Community -
League -
Photos -
Cameras -
Lenses -
Learn -
Help -
Terms of Use -
Privacy -
Top ^
DPChallenge, and website content and design, Copyright © 2001-2025 Challenging Technologies, LLC.
All digital photo copyrights belong to the photographers and may not be used without permission.
Current Server Time: 06/17/2025 02:59:50 AM EDT.
