In message , Andy Burns
wrote
chili-girl wrote:

For a normal CCTV camera (that is linked to a PC capture card) and on
a fine sunny day. Is there a typical distance you can read a number
plate.

Depends on the focal length of the lens ...

Assume you need the plate to be approx 10% of the image width to read
the plate (giving approximately eight pixels per character on the
plate) lets round the plate dimensions up to 1.5', so you need a field
of view of 15' to achieve the plate being 10% of the image.

For a 1/3" sensor you'd need a lens of 26mm focal length to give a
field of view of 15' at a distance of 82', unfortunately your 3.5-8mm
zoom lens isn't going to cut it.


It may need a lens with a longer focal length (longer than 26mm) as the
camera/lens combination has a resolution lower than a pixel count
suggests.

At night power of the illumination at 25m would have to be adequate and
a ' ring of leds' would probably be insufficient.

The alternative is to get some software such as is used in CSI where you
will be able to read a whole number plate from a single pixel in the
source video.
--
Alan
news2006 {at} amac {dot} f2s {dot} com