question about security camera performance

Can anybody direct me to some good information to compare camera
specifications ?  For example many cameras will give you a lux rating and
say it will work down to 1.0 lux light or 0.5 lux light, but I haven't been
able to discern what that means in the real world.  I've found the technical
definitions of lux, foot-candles, etc, but have a hard time seeing what that
means in the real world.  Will a 1.0 lux B&W camera show anything on a
moonlit night ?  Moonless night ?  Also how do you convert the lens size to
a magnification power or angular field of view ?  Things like that.

I would appreciate any pointers to info about camera performance and optics
for the embedded engineer layman.

Eagle Eye <ee@nospam.net> wrote:

> Also how do you convert the lens size to a magnification power or
> angular field of view ?  

You don't.  Those have nothing to do with each other.  The size of the
lense governs only the sensitivity (basically: the larger the front
hole, the more light your camera collects --> the more sensitive it'll
be).

Cameras don't have "magnifications", anyway.

As to what a Lux means: 

http://www.wordiq.com/definition/Lux


-- 
Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de)
Even if all the snow were burnt, ashes would remain.

Eagle Eye wrote:

> Can anybody direct me to some good information to compare camera
> specifications ?  For example many cameras will give you a lux rating and
> say it will work down to 1.0 lux light or 0.5 lux light, but I haven't
> been
> able to discern what that means in the real world.  I've found the
> technical definitions of lux, foot-candles, etc, but have a hard time
> seeing what that
> means in the real world.  Will a 1.0 lux B&W camera show anything on a
> moonlit night ?  Moonless night ?  Also how do you convert the lens size
> to
> a magnification power or angular field of view ?  Things like that.
> 
> I would appreciate any pointers to info about camera performance and
> optics for the embedded engineer layman.

Sounds like someone needs to do some experiments in a darkened room. I did 
this sort of thing a very large number of years ago when we were developing 
an emergency lighting scheme. Fortunately we had a large photogographers 
studio, which could be blacked out completely, at our disposal and suited 
our needs. You need to experience it to know it as I would find it 
difficult to convey in words.


-- 
********************************************************************
Paul E. Bennett ....................<email://peb@a...>
Forth based HIDECS Consultancy .....<http://www.amleth.demon.co.uk/>
Mob: +44 (0)7811-639972 .........NOW AVAILABLE:- HIDECS COURSE......
Tel: +44 (0)1235-811095 .... see http://www.feabhas.com for details.
Going Forth Safely ..... EBA. www.electric-boat-association.org.uk..
********************************************************************

In article <clee47$3om$1$8302bc10@news.demon.co.uk>, 
peb@amleth.demon.co.uk says...
> Eagle Eye wrote:
> 
> > Can anybody direct me to some good information to compare camera
> > specifications ?  For example many cameras will give you a lux rating and
> > say it will work down to 1.0 lux light or 0.5 lux light, but I haven't
> > been
> > able to discern what that means in the real world.  I've found the
> > technical definitions of lux, foot-candles, etc, but have a hard time
> > seeing what that
> > means in the real world.  Will a 1.0 lux B&W camera show anything on a
> > moonlit night ?  Moonless night ?  Also how do you convert the lens size
> > to
> > a magnification power or angular field of view ?  Things like that.
> > 
> > I would appreciate any pointers to info about camera performance and
> > optics for the embedded engineer layman.
> 
> Sounds like someone needs to do some experiments in a darkened room. I did 
> this sort of thing a very large number of years ago when we were developing 
> an emergency lighting scheme. Fortunately we had a large photogographers 
> studio, which could be blacked out completely, at our disposal and suited 
> our needs. You need to experience it to know it as I would find it 
> difficult to convey in words.

Many CCD cameras are sensitive to infrared.  You can make an extremely 
bright illuminator using some IR LEDs that will be invisible to the 
human eye.  Many "baby-cams" have them built-in.

--Gene

On 22 Oct 2004 20:50:09 GMT, Hans-Bernhard Broeker
<broeker@physik.rwth-aachen.de> wrote:

>Eagle Eye <ee@nospam.net> wrote:
>
>> Also how do you convert the lens size to a magnification power or
>> angular field of view ?  
>
>You don't.  Those have nothing to do with each other.  The size of the
>lense governs only the sensitivity (basically: the larger the front
>hole, the more light your camera collects --> the more sensitive it'll
>be).

The lens "size" is an indication of magnification as used in the
photographic world. a 50mm lens does not imply that the diameter of
the lense is 50mm. In the 35mm SLR world it implies a magnification of
x1. The F-stop of a lense gives an indication of the physical size.
i.e a 50mm lense with an F stop of 1.4 will have more light gathering
power than a 50mm lens with an F stop of 4.

>Cameras don't have "magnifications", anyway.

A camera is a sensor with an element to focus the image onto the
sensor. A CCD sensor alone is NOT a camera.

Regards
   Anton Erasmus