Ime looking for a day night camera with perfect {or near enough} resolution, that can read number clearly from about 10 to 20 metres, what should i be looking for spec wise ? big lens more lines ime stuck again.

10 or 20 meters ? - your going to need to decide which first

20mtrs

12mm lens, 420tvl +

depends what your trying to read.

is it numberplates?

predominantly day time, nightime or both. If its general viewing I would always go with a high res day / night, ex-view chipset and moveable ir cut filter.

If your trying to get numberplates a proper number plate capture camera is best but they can cost a thousand to many thousands of pound. As a rule of thumb, numberplate capture should be 50% rotakin or better or 2m target width.

Try this quick calculation for determining focal lengths:

Focal Length = (Chip size x distance to target) / Target width

chip sizes are: 1/3" = 4.8, 1/4 = 3.6

In your example, on a 1/3" chipset and 2m target width would be:

at 10m: (4.8 x 10) / 2 = 24mm focal length

at 20m: (4.8 x 20) / 2 = 48mm focal length

a 5-50mm varifocal lens should be adequate.

Edited February 10, 200818 yr by sjonley

Thank fer that ime lookin on the net fer a 12mm cam with about 450tvl....

Thank fer that ime lookin on the net fer a 12mm cam with about 450tvl....

so you dont want to read number plates then ?