is there a way to find out specs of lenses just by inspecting visually?

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I recently acquired some CCTV lenses like the one in the picture. there is no writing on it, I was wondering if there is a way to figure out the specs by inspecting visually.
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bp2008

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Maybe with specialized equipment you could tell, but I wouldn't even know what to suggest.

Chances are the quality of random unmarked lenses isn't very good anyway, so even if they turn out to be compatible with a modern IP cam, they might not focus very well and might not be IR-corrected. Also some lenses have permanent IR filters built in.
 

pozzello

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If you have other lenses of known specs, ie, one that's known to be 4mm, etc, you can compare by shining a laser-pointer type light thru it from the back end and see how far it disperses (at a fixed distance from the projection surface, of course). So, holding the lens 6" above a sheet of paper or other surface, the 4mm lens will throw a narrower image than a 2.8, for example...
 
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