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How To Figure Out What MM Lense I Need

Getting Started

You may have noticed that many of our cameras are available with different lenses.  Common size lenses are 3.6, 6, 8, 12, 16, 25, and 35mm.  You also may not know which one is right for you. The goal of this article is to address that.

Before you can know mm lense you need, you need to understand what it means.

How Different MM Lenses Affect Your Picture

The larger the mm lense, the more narrow your field of view. This means that a 3.6mm lense will have a wider field of view than a 6 mm lense and that a 12mm lense will have a more narrow field of view than an 8mm lense.  The key to remember is the larger the mm lense, the more narrow the field of view.

Some people have a hard time grasping a field of view.  An example which helps people is taking a family picture.  You can pull back and view the whole family, but each person will be pretty small.  This is a wide angle field of view, which is what you would get from a 3.6mm lense.  Or, you can zoom in an individual's face.  You'll see the face clearly, but you won't see anyone else on either side of them.  This is a narrow field of view, which is what you would get from a 12 or 16mm lense.

Determining What Lense You Need

To determine what mm lense you need, you will need to know two things.
  1. The distance away of what you're trying to see
  2. The width you need at that distance
You may have to measure or you might already know. For example, if you're trying to watch a door, and the camera's 50ft ft away from the door, then you know you need to see a 3ft width (the door) at 50ft away.  Another example: If you're trying to watch a vehicle gate.  You know the camera will be 25ft away from the gate, and the road width is 15ft.  Then you know you need to see 15ft wide at 25ft away.  These are the types of dimensions you need.

Once you have this information in hand, the rest is easy.  You can go to our FOV calculator page or use the on page tool on all of our security camera pages. Enter in the width and distance, and it will shoot out the exact mm lense you need.

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