On 21/10/2014 10:54, DerbyBorn wrote:
I have noticed many CCTV cameras have a ring of LEDs around the lens - but
behind a front glass (Saw this on a drone which made me wonder....)
Can the LEDs be of any use given the sort of useful distance that the
camera is expected to focus on? Does having the LEDs behind the front glass
cause scatter off dust and moisture to ruin the image. Are they just a
gimmick?
(a bit like using a flash on a camera at a stadium concert - see Inverse
Square Law of Light)


On most of them the lens has a shield to stop the leds reflecting back
into the lens.

They can be designed to illuminate from 5m to 120m but not at the same
time. You decide what when you order the camera and lens combination.
Wide angle lenses need wider illumination and have a shorter range.