A bacon enlarger is just a mallet and a flat surface !
So, I'm wondering how you managed the film being wet for exposures, presumably it had to go back onto a second roll as it passed through, was it dried somehow ?
Those 40x40" prints must have really been something to see ?
Lots of interesting info in here. A few brief notes on the microdensitometry process, 1B sensitometer light path, application of special thin emulsion layer to prevent Newton ring formation, etc. Thanks for posting.
Actually , correction above, it was probably a matching oil, not water , used for the enlargements - but a similar issue...
I read about 30 pages today. Some mind-boggling stuff. Super-thin estar base layers to get payload-compatible reels of film that were 6000ft+ in length. Processing machines that could (eventually ) make automated frame-by-frame N-1 to N+1 development adjustments. High-res duplicating film that was exposed by two different UV mercury lines to get a sort of 'Multigrade' effect to control copy contrast. So much work and talent went into this !
Not sure if they mention it in this doc but if I remember correctly the fluid was tetrachloroethylene.
Originally Posted by Mark J
Ah, right - so would that evaporate quickly when you moved the frame on ?
Military technology is far ahead of civilian technology - but over the years the civilian world catches up; semiconductors are an exception.
Darkroom Automation / Cleveland Engineering Design, LLC
f-Stop Timers & Enlarging meters http://www.darkroomautomation.com/da-main.htm
Yes it’s basically dry cleaning fluid and it happened to have the right index of refraction.
About the BPE's lenses. There were eight different ones for different magnifications, each with their own matching condenser. You could make enlargements from 3x to 153x, depending on which lens/condenser set you used. They were designed to be diffraction-limited at their single, fixed f/stop, and were built in large and heavy barrel mounts. Focusing was by helical, a method too complicated to explain here (the training course took the better part of a week). Kodak used thorium glass for some internal elements. It was a cost-no-object device, designed to be reach the theoretical limits of enlargement, which I suppose it did. Certainly no conventional enlarger came close for its very specialized purpose (we had plenty of those too).
Of course it was useless for conventional enlarging; I wonder if any are still in use, or even if any still exist.
Last edited by Mark Sampson; 23-Mar-2023 at 19:42.
I left the DIA photolab in 1994, left the agency in 2011. I think they had the BPEs up until 2000 or so, but no idea what happened to them after that. I don't think they ever went to government surplus...
It would be rather cool to have one in the garage to surprise your photo friends !
I can imagine that focusing the high-mag lenses would have been as critical as for a microscope objective. I think they probably used a liberal selection of materials, including flourite in there, getting something to resolve >500cy/mm over 0.3" format is very much non-trivial, I did a design for something mad like that once, but the customer didn't have the stomach for it !
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