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Guide to Closed Circuit TV (CCTV)

So would you like to play "Spot the CCTV Camera?". Eagle eyed visitors may recognise the profusion of street furniture, surrounding a single heritage dome camera keeping watch over part  of Londons' prestigious Oxford Street shopping area.

All you need to know about lenses,
for all types of video surveillance.

BARREL LENSES for Printed Circuit Board (PCB) Cameras

Some Printed Circuit Board (PCB) cameras (and indeed a limited number of ‘Bullet’ cameras) have the option of fitting small interchangeable lenses. These optics are somewhat limited in range, and it has to be said, rather limited in performance.

Basically there are two versions of the same lens design. They are identical in that all of the lenses have a fixed iris, so there is no opportunity to ‘stop down’ the lens to prevent imager overload, and improve the overall optical performance.

They differ only in the way they are fitted to the camera. One version uses a smooth barrelled mount which holds the lens in its correct position using tiny grub screws. To set the correct focus, the screws must be loosened using either jewellers screwdrivers, or a miniature hex allen key (as appropriate), and the lens is then manually pushed or pulled into the correct position, before the screws are finally re-tightened (fiddly or what!!)

The other version is identical save for a fine helical thread around the lens barrel. The advantage of this arrangement is that the lens can be gently twisted to achieve the correct focus setting, before (again) being ‘locked off’ using the small grub screws; so much easier to set up, you have to wonder why all cameras that use this type of lens don’t standardise on the threaded version.

Whilst these mini optics are designed and manufactured down to a price, they are generally not staggering in terms of performance. If you bear in mind that they are really only ever going to be used on standard resolution or basic performance cameras, what they do, they do adequately.

With Doktor Jons limited experience of using these lenses, the ultra wides tend to provide a surprisingly good overall level of performance, with the telephoto’s also offering a reasonable quality of image for such a low cost optic.

It must be remembered that these lenses are not designed or intended to ‘set the world alight’, but if used sensibly, particularly with indoor ‘visual verification’ applications, they are generally pretty much ‘ok’ for the job.

Manual Iris Lenses for Industrial Cameras>

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