lens review please

[ShagMan]

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]

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.

 

[Mikey p]

Navitar has Buhl lenses. They may be able to give you some information on the lens.
http://www.navitar.com/contact_us.htm

 

[ShagMan]

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.

 

[SmC252]

f3.3 * 4 = 13.2" Not bad at all!

 

[tgreenwood]

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.

 

[ShagMan]

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!

 

[SmC252]

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]

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?

 

[mihari]

hi all, newbie here!!!

what do you think a "102mm 152mm f:3.5" zoom lens does?
aren't 102mm and 152mm the actual efl distances?