Re: Video quality for security - camera lines

[Jim Noble <yahoo-groups@xxxxxxxxxxxxxxxxxx>]

ian.bird@xxxxxxx wrote:
> Anyway, having looked round I am now thinking of what cameras to get
> assuming I get a DVR based system. I have found systems which include
> cameras but the choices for outdoor cameras seem limited to 380 or 420
TV
> lines. I have not been able to find examples of the output from these
> anywhere. Does anyone have recommendations as to what spec camera to
get.
>

Bear in mind that the "TV Lines" metric is the horizontal line
resolution. So a 380 line camera is only just over half the full linear
PAL horizontal resolution (720 "lines"). If you're only going to
be
recording at 1/4 PAL, that isn't going to matter too much.

> I need external with night time IR and ideally available in different
lens
> specs giving different angles of view. Not a zoom camera as these are
> silly prices.
>

You *really* want a camera with infra-red cut filter removal then. My
so-called "IR-sensitive" mini dome really doesn't see anything
much in
near dark conditions, even if lit by a fairly bright IR source. (I get
grainy black and white with the porch light on though).

I now have some dome cameras with the proper IR cut filter, and early
results show that the difference is quite significant.

An auto-iris lens is much better than the electronic iris ones, and
varifocal ones are cheaper than zoom ones. 3.6-8mm is a good range to
aim for (covers ~35-90 degrees of view).

> I have not been able to find out if the extra resolution from say a
480 TV
> lines camera over a 380 or 420 will look any different once recorded
onto
> the DVR. I am looking for facial recognition if the worst came to the
> worst so detail may matter but only if it is recorded accurately.
>

1/4 PAL isn't really going to cut it for facial recognition, unless
you're recording a very close up image (and the perp is cooperative
enough to stay in frame!).

There are cameras available now that claim >500 TVL, in colour well into
dusk, and black & white in fairly low light conditions. (eg some of the
latest Samsung Techwin cameras with the "Winner III" DSP). They
seem to
be tricky to get hold of on the retail market though.

Jim