RE: Security Camera questions

["James Hoye" <james.hoye@xxxxxxx>]

> Security cameras. I assume I should be looking at Resolution and
> Lux figures
> to work out the quality of the camera, but what is a good resolution
and
> what is a good Lux? (some of the cameras on the above mentioned site
have
> 'Min. Illumination 0.05 Lux at f1.2' what's the f1.2 mean?)

f1.2 (or more correctly, f/1.2) relates to the aperture size.

It is expressed as the ratio of the lens focal length (in mm) to the
diameter of the aperture (in mm).
For instance, on a 35mm SLR camera, a 50mm f/2.8 lens would have an
aperture
diameter of 17.86mm, exposing an area of light approx 250.5 sq mm.

A 50mm f/2 lens would expose an area approx 490 sq mm thereby allowing
twice
as much light through.  This would make it able to operate at half the
level
of light of a 50mm f/2.8 lens.

James H



http://www.automatedhome.co.uk
Post message: ukha_d@xxxxxxx 
Subscribe:  ukha_d-subscribe@xxxxxxx 
Unsubscribe:  ukha_d-unsubscribe@xxxxxxx 
List owner:  ukha_d-owner@xxxxxxx
List of UKHA Groups here - http://groups.yahoo.com/group/UKHA_Grouplists/

Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.