So I have this Day/Night box camera that I am going to buy a new lens for (I am looking for vari-focal and auto-iris).

I came across these two lenses that interest me -- one is day/night, and one is not:

http://www.cctvimports.com/lenses-vari-focal-c-23_92/fujinon-2-9-8mm-day-night-vari-focal-dv-auto-iris-lens-p-334

http://www.cctvimports.com/lenses-vari-focal-c-23_92/fujinon-2-7-13-5mm-vari-focal-auto-iris-lens-p-337

What is the difference between a Day/Night Lens and one that is not? I know the difference between a day/night camera and one that is not. Is the lens just corrected to give a clearer picture when IR is present? Does a day/night lens have a built in IR cut filter? and if so, then i probably wouldnt need it if my camera already has this technology, right?

More importantly, do I 'NEED' a day/night lens for a day/night camera that has an IR Cut Filter, or will a regular lens work also?

Hello,


Exactly. Clearer, sharper, in focus.
In normal lens IR focuses in another point, than the visible light and so picture could not be sharp.
http://www.isorainbow.com/tech/day_night_info.htm


No, it has not.


It is not an obligatory, but if I can, I always use such lenses with cameras with IR cut filter.
IR is always present around us, many light sources gives small amount of IR too,
so I prefer to use such lenses.
When IR lighting is used, You have to use such lenses to obtain clear and sharp image.

Regards.

Yep, halogen/incandescent lighting produces a lot of IR and you will get a clearer image of faces from any camera with an IR-comped lens, in particular a day/night in night mode since none of that IR is filtered out.

Got it.

Thanks guys