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Choosing the Right Lens for Your Video Surveillance Cameras

By Jon Benowitz on November 5, 2013 in Surveillance Cameras, Uncategorized
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The lens that you choose for your video surveillance camera setup is going to depend upon what you are viewing and the type of surveillance setup that you will be running.  It is often easy to make the wrong lens choices when you misunderstand the confusing terminology.  Also, at times it can seem as if retailers are expecting you to have a full understanding of the terminology without providing the proper guides.  Misinformation spreads easily in the video industry, particularly when it comes to lenses.  There are a few things that need to be taken into account throughout the process of choosing a lens to ensure that you are able to have a high quality picture that is able to protect your property to the best of your ability.  Take the following tips into account when choosing a lens for your video surveillance efforts;

Sensor Size for CCD

When you are looking at different lenses, the most important thing that you need to take into consideration is going to be the CCD sensor size.  The CCD sensor size is going to affect the overall picture quality of your surveillance.  The sensor size is important because it determines how to focus the image on the surface of the sensor.  If you were to make the wrong choice in terms of the size of the lens, you can deal with variations in the images, including images being unnecessarily cropped when the image is too large for the sensor, or the barrel of the lens showing in the picture when the image is too small for the sensor.

A vast majority of CCD cameras will work great with a 1/3” sensor, although there are a variety of sizes that could be the right choice depending upon the model of the camera.  Make sure to check into what documentation the camera manufacturer provides to see if they have a recommendation regarding which CCD sensor size you should be looking for.

Irises

Another consideration that needs to be taken into account when you are looking at lenses is going to be the iris of the lens.  You have to determine whether or not you are going to be using a manual or an automatic iris.  The iris sits within the lens and adjusts to the shutter speed of the camera, based on how much lighting is available in the area.  When you are using an automatic iris on your camera, in many ways it performs very similar to the way that the human eye operates.  An automatic iris is not supported by all lenses, but usually performs better in conditions in which the light conditions vary rapidly.  Depending upon the type of automatic iris, either Video or DC, not all types of automatic irises are compatible with all CCTV video systems. Many lenses will support both types of irises, but it is important that you check your documentation.

Focal Length

The focal length of the lens is another important consideration when putting together your entire system.  The focal length refers to the distance from the center of the lens to the focal plane that is contained within the camera.  The focal length is directly responsible for the field of view and the depth of field of your camera.  The correct focal length will depend upon the scene in which you will be shooting.  Reading about the technical details of focal length measurements can help you to determine exactly which focal length will be best for you depending upon what you will be filming.  The focal length has a direct impact on the quality of your video, which will determine the level of security that you are able to provide.

Field of View

The field of view is another very important consideration when you are examining the different lenses that are available to you.  First, you have to take the angular field of view of the lens into account.  The angular field of view refers to the angles in which light can go through the lens, creating an image on the sensor.  This depends upon a number of different factors, including the focal length, and also the dimension of the sensor.

Depth of Field

The depth of field refers to the distance behind the ‘main object’ that items will appear in focus. It is easy to see why this is a very important consideration when you are setting up security or surveillance.  You want as many objects to be in focus as possible, particularly when you are viewing a large area.  You want to be sure that as many items are in focus as possible so that you can keep a close eye on the property and get all details in crystal clear focus.  A wider depth of field helps to ensure that the entirety of the scene remains in focus.  A shallow depth of field will only keep specific areas of the scene in focus. The depth of field is mostly affected by the f-number of the lens.  The f-number is a number that refers to the ratio of the focal length compared to the diameter of the pupil of the lens.  The f-number plays a key role in lens speed.

There are many key considerations that must be taken into account when you are looking for a lens for your video camera security setup.  There is a lot of misinformation available online and you need to make sure that you are properly informed regarding all of the different aspects of choosing a lens.  Remember to refer to documentation from your camera manufacturer to ensure that you are able to look at all of the available options and determine not only which lenses will be the best for your particular camera, but also which lenses will be best for your security setup.  Take your time, conduct the necessary research, and find the best possible lens for your security setup.

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Jon BenowitzView all posts by Jon Benowitz

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