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
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
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: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!
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:
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.
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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