On 08/06/2018 10:43, Dave Plowman (News) wrote:
In article ,
dennis@home wrote:
Its just a case of getting the exposure correct.
To do so may be impossible with some cameras.

It's not. Having the light source - in this case infra-red - beside the
lens means it reflects straight back into the lens.

If the IR illumination and camera were perpendicular to the number plate
I would agree, but that would be unlikely. The only other issue is with
snow/rain/fog where there is significant local reflection.

The contrast between white and black on a number plate is significant,
it really is a question of getting the right illumination and correct
shutter speed.

Some illegal number plates try and filter the IR wavelengths to reduce
the contrast, but they are still readable in the visible.

I might be more tempted to use white or yellow illumination, which would
also act as a deterrent.