lens review please

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ShagMan

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Joined 2005
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
 
Rox

Rox

Member
Joined 2004
nobody will tell you the fov of this lens, even the lens we know the fov form the manufacturer are disscusion tophics :D.

The answer; try it yourself and share. :D

i would say it is near 15" the max you can use it with, and take care of the throw.

good luck.
 
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ShagMan

Member
Joined 2005
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!
 
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SmC252

Member
Joined 2005
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!
Click to expand...

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.
 
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SmC252

Member
Joined 2005
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.
Click to expand...

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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