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View Full Version : Largest, fastest wide angle lens for ULF?



Jac@stafford.net
22-Aug-2018, 16:16
Largest, fastest wide angle lens for ULF? I might have it. It is a monster.

Front element and rear elements about 16" in diameter, with the front being convex and the rear concave. In steel mount. Super clean, not even dust.

Military origin. Any clues as to what I have are welcome.

Dan Fromm
22-Aug-2018, 16:22
Is this your window again?

MAubrey
22-Aug-2018, 16:28
Focal length?

Alan Gales
22-Aug-2018, 16:52
I don't know, Jac, but be sure to eat your Wheaties before you pick it up! ;)

Randy Moe
22-Aug-2018, 17:32
Itís a bomber window for taking pics.

I have handled one.

Randy Moe
22-Aug-2018, 17:39
I also think itís very cool. I wanted to install it in a video edit stall so we could spy at the computer nerds. The last 2 I saw sell on eBay recently went for very low prices considering how interesting they are.

Dan Fromm
22-Aug-2018, 18:33
I'd swear I've asked Jac whether his forms an image and got no response. Randy, did the one you saw form an image?

Randy Moe
22-Aug-2018, 18:52
I never tried to find focal length as it seemed to be very short. 2 concave Perspex both facing out for air pressure I presumed.

Jac would know more.



I'd swear I've asked Jac whether his forms an image and got no response. Randy, did the one you saw form an image?

neil poulsen
23-Aug-2018, 08:07
Photos of the lens?

Dan Fromm
23-Aug-2018, 10:22
We've been here before. See http://www.largeformatphotography.info/forum/showthread.php?146017-Monster-lens-or-a-window&p=1444629#post1444629

Mark Sawyer
23-Aug-2018, 12:54
Same as this?

https://www.ebay.com/itm/WWII-Military-Plane-Bomber-Machine-Gunner-Window/302706241267?hash=item467ab2aef3:g:9J8AAOSwhTBa08il

If it's a "wide-angle window", it's a negative lens and won't form an image.

Dan Fromm
23-Aug-2018, 13:30
The very one. For more details, see the link in post #10 above.

Randy Moe
23-Aug-2018, 14:34
Same as this?

https://www.ebay.com/itm/WWII-Military-Plane-Bomber-Machine-Gunner-Window/302706241267?hash=item467ab2aef3:g:9J8AAOSwhTBa08il

If it's a "wide-angle window", it's a negative lens and won't form an image.

That's exactly like what I held in my hands.

Jac may have something different.

Dan Fromm
23-Aug-2018, 14:46
That's exactly like what I held in my hands.

Jac may have something different.

Take a look at the discussion the link on post #10 above points to.

Randy Moe
23-Aug-2018, 15:32
Take a look at the discussion the link on post #10 above points to.

I have thrice

Let Jac speak for himself.

Dan Fromm
23-Aug-2018, 16:27
Thrice? Wow! Its been a while since I've seen the word.

Randy Moe
23-Aug-2018, 16:40
Thrice? Wow! Its been a while since I've seen the word.

As a child, I read the dictionary, but I am still a bad speeler and typist. :cool:

Jac@stafford.net
23-Aug-2018, 19:37
I am temporarily handicapped: I hope it is temporary (it is a periodic thing) so showing the window's image must wait until I have some help. I now have two of them, and for fun I'm speculating if I place them back-to-back they might make an interesting symmetric lens. :)

The inventor of this also patented a proper and huge lens based, in part, on my lens/window.

Dan: Thrice is a real word to us old (over 70 YO) proper English speakers. I know of no such in Canuck, my only vaguely familiar family language.

Mark Sawyer
24-Aug-2018, 08:56
...I now have two of them, and for fun I'm speculating if I place them back-to-back they might make an interesting symmetric lens. :)

As these are negative lenses, and since two negative lenses don't make a positive, I'm afraid not. Perhaps if you could separate positive elements it could be done, but I suspect these are single-element negative menisci. :(

Jac@stafford.net
24-Aug-2018, 09:38
As these are negative lenses, and since two negative lenses don't make a positive, I'm afraid not. Perhaps if you could separate positive elements it could be done, but I suspect these are single-element negative menisci. :(

I will disassemble the used one.
Here are some pics.
http://www.digoliardi.net/b-25/windoiw-pics/c.jpg
http://www.digoliardi.net/b-25/windoiw-pics/b.jpg
http://www.digoliardi.net/b-25/windoiw-pics/a.jpg

http://www.digoliardi.net/b-25/windoiw-pics/illustration-1.jpg

Mark Sawyer
24-Aug-2018, 11:56
http://www.digoliardi.net/b-25/windoiw-pics/illustration-1.jpg

That cross-section shows two elements, both thinner in the middle than the edges, so both are negative/dispersive lenses. Sorry, just ain't gonna work. :(

Jac@stafford.net
24-Aug-2018, 13:46
That cross-section shows two elements, both thinner in the middle than the edges, so both are negative/dispersive lenses. Sorry, just ain't gonna work. :(

Thanks for that, Mark. I'm glad I asked. What if I remove the rear element?

As-is it will at least be one impressive door peephole. :)

Mark Sampson
24-Aug-2018, 14:21
Time to find a couple of positive lenses of similar diameter, and commit some optical mayhem!

Jac@stafford.net
24-Aug-2018, 16:31
Time to find a couple of positive lenses of similar diameter, and commit some optical mayhem!

That is a challenge! By chance I do have two opposing 15" condenser lenses, but no other big glass. Me thinks these lenses, or whatever they are, are candidates to my remote storage locker.

Very good being in touch, Mark.

(OMG, I just remembered that I have traffic light lens that throw a beam far away. I'm considering incorporating them into the tail lights of my home-built car. :)) It is the one on the right here (http://www.digoliardi.net/brad/the_bugs.jpg).