I just snapped this up on eBay (had to outwit the other snipers heh)... the FL and F specs seem OK, but I couldn't find a good calculator to see what the FOV would work out to... Can somebody help me out, what's the diameter this thing can see?
Buhl Optical Lens NO. 689-12.5, F: 3.3, 12.5 in E.F.L.
The diameter is ~4", and I'm guessing the 12.5 in means 12.5" FL?
I'm hoping I didn't inadverdantly pick up a CRT Projector lens!
Here's the closed auction link, with a few pics:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7512241468
Buhl Optical Lens NO. 689-12.5, F: 3.3, 12.5 in E.F.L.
The diameter is ~4", and I'm guessing the 12.5 in means 12.5" FL?
I'm hoping I didn't inadverdantly pick up a CRT Projector lens!
Here's the closed auction link, with a few pics:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7512241468
nobody will tell you the fov of this lens, even the lens we know the fov form the manufacturer are disscusion tophics 😀.
The answer; try it yourself and share. 😀
i would say it is near 15" the max you can use it with, and take care of the throw.
good luck.
The answer; try it yourself and share. 😀
i would say it is near 15" the max you can use it with, and take care of the throw.
good luck.
Navitar has Buhl lenses. They may be able to give you some information on the lens.
http://www.navitar.com/contact_us.htm
http://www.navitar.com/contact_us.htm
Actually, Navitar IS Buhl, to an extent... bought them out in '97 according to their "about us" / company timeline page... I sent an email to a few addresses on the contact page, good idea.
Big lens.....
It looks like an opaque projector lens from one of the older opaque projectors. I have one that looks a lot like it, similar dimensions, but has an 18 inch effective focal length.
Here's one on Ebay....opaque projector lens
T.
It looks like an opaque projector lens from one of the older opaque projectors. I have one that looks a lot like it, similar dimensions, but has an 18 inch effective focal length.
Here's one on Ebay....opaque projector lens
T.
I got this lense in today, and it is indeed 12.5" FL, F3.3, it's awesome!!! Definitely a steal, I picked it up off eBay for under $50. I agree it looks like it was for some sort of opaque projector... Now if DPC would get in some 330mm fresnels, I'd be in good shape!!!
EDIT: done some testing, and not sure about the focus, it's VERY tricky to focus... it's also a doublet (I think) and the back lens is flat/no curves, weird!
EDIT: done some testing, and not sure about the focus, it's VERY tricky to focus... it's also a doublet (I think) and the back lens is flat/no curves, weird!
ShagMan said:
Isn't 3.3 your f/4? If it is, then you multiply it by 4, as it's the focal length divide by 4, and you get the actual FL. 13.2" is what it should be unless that isn't the f/4.
SmC252 said:
I don't think your "f3.3" is what I was thinking it was. I was thinking of f-stop and how you can convert it to get your focal length. What is that "f" standing for?
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