In article ,
Fredxx wrote:
On 08/06/2018 15:41, Dave Plowman (News) wrote:
In article ,
Fredxx wrote:
On 08/06/2018 14:56, Dave Plowman (News) wrote:
In article ,
Fredxx wrote:
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.

Car number plates reflect light from more than one direction.

By law the letters shouldn't, nor should any coating be added to make
the letters retro-reflective. So the contrast should be huge.

But reflecting the light source straight back down the lens also gives you
a problem with auto exposure. Not much point having a picture where the
only thing you can see is the number plate.

For Cynic's purposes the solution might likely to be more than one
camera. One with exposure specifically to capture the number plate, and
another to see what was going on.

There are cameras than can cope with a huge dynamic range, but they're
not cheap.

That's the problem with many solutions. Not cheap enough.

--
*The last thing I want to do is hurt you. But it's still on my list.

Dave Plowman London SW
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