Tips About CCTV Lens Features
By Christian M Gillman
CCTV lenses have a lot of different features and it is a good idea to know some of the different ones available and how they affect your surveillance system or your security cameras. So before purchasing a cctv lens for your camera, take the time to read through this and gain some insight to some of the more popular features and what they do.
There are few different types of CCTV lenses out there including C/CS, M12, & M9; we will be going over features and styles indicative of the C/CS mount style however, as they are the most common and applicable.
The main difference between these types of lenses that you should know about is that M9 and M12 are board type lenses used with board, miniature, and bullet style security cameras; whereas C/CS mount lenses are used on C/CS mount cameras.
Additionally M9 and M12 lenses are usually set focal length lenses, and they will have to be replaced with a new lens to have a different focal length. We will talk more about varifocal vs. fixed focal length later on.
To begin with when someone is talking about a lens focal length, it is related to how wide or narrow your image angle will be. The smaller a lenses focal length, then the wider the image viewing angle will be. Adversely the larger the focal length, the narrower your viewing angle will be.
Tying into focal length is fixed vs. varifocal type lenses. A varifocal lens has a range of focal lengths that it can be set at to help you get the best viewing angle for your application. A fixed length however is made to be used at one focal length and cannot be made to be wider or narrower if needed.
An example of a varifocal lens would be one advertising a 2.9mm - 8mm length; this indicates it can be set at any focal length within that range. A fixed lens would be advertised as something solid such as 4mm, 6mm, 2.8mm, etc...
Auto Iris vs. Manual
The iris is a device on your lens that determines how much light the lens will allow in, just as the iris in your eye does. In bright situations an iris needs to be smaller so as not to over expose an image; where as in dark situations the iris will be bigger to allow in as much light as possible to make a clearer image.
A CCTV lens with an auto iris feature can sense and automatically adjust its iris in accordance with how much light is present. A manual iris lens on the other hand is better in conditions where the light is unchanging, as it needs to be manually set to the correct exposure.
Auto Focus vs. Manual Focus
Just as with an auto iris, a lens with an auto focus is able to adjust its picture to gain a focus on an object automatically. This is useful if you don't mind a wide focus range, but if you want your focus to be specific on a certain object, then you will want to be able to adjust your focus manually.
There are a number of other features that lenses have, and if you are confused by any of them it may be a wise choice to consult a surveillance dealer such as Industrial Covert Unlimited before purchasing.
Christian M Gillman has worked in the surveillance industry for over 6 years. Subscribe to our monthly newsletter, learn more about surveillance, and find great products at http://www.cu1.com
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