Which Security Camera Lens Size Should I Buy?

⚡⚡⚡⚡Amazon Links:⚡⚡⚡⚡
25X Dome: https://amzn.to/2qiKkyQ
Hikvision Bullet Cameras: https://amzn.to/32ydLAl

💻💻💻💻💻 Blue Iris (Security Camera Video Management Software): http://hometechdiy.com/buy-blue-iris/
Trigonometry to help figure out viewing angles: https://www.mathopenref.com/trigtangent.html
Reolink’s lens choice guide: https://reolink.com/how-to-choose-best-security-camera-lens/

My Blog post for more information on lens sizes: http://hometechdiy.com/security-camera-lens-sizes/

Today’s topic is security camera lens sizes. I’ll show the difference between a wide angle 2.8mm lens all the way up to a 12mm zoom lens. In particular, I’ll review camera footage, the difference between fixed and variable lenses, the math behind lens sizes, zoom multipliers, sensor size impacts on viewing angles, minimal focus distances and lastly, we’ll check out if the lens size has an impact on the camera’s infrared night vision. All that should provide you with everything you need to know about security camera lens sizes.
Fixed Camera Lens means the lenses don’t move. There no zooming in or out and no way to change their focus. Their fields of view or their coverage area is constant. Another name for these would be mono-focal cameras. I show a bunch of examples using a wide angle 2.8mm, 4mm, 6mm, all the way up to a zoom camera with a 12mm lens.
I also show many examples with a Varifocal Camera. It has an internal lens which does move. Its zoom level and focus are controlled through its app and it’s called a varifocal camera.
Showing many examples of nighttime footage in important to better understand the nighttime expectations for each lens size.
These are bullet style cameras, and the lens principles apply to all types (domes and turrets). On the front of the camera, we have the lens, and its not meant to be removed or interchangeable. They are usually sealed and if you break that seal it’s very challenging to re-focus the camera.
A camera’s lens size, is also referred to as the focal length. This is the distance between the back of the lens and the camera’s sensor, and it’s measured in millimeters. By comparison, there are 25.4mm in 1 inch, so when we talk about 2.8mm, we aren’t talking a very large space.
Let’s chat about varifocal cameras a little more. As I change the distance between the lens and the sensor, you can see two things happening. 1) The field of view is becoming narrower and 2) the camera needs to re-focus to ensure a sharp image at the new focal length. This is an advantage to varifocal lenses over fixed lenses, as we’ll see shortly when we test the minimal focal distances.
These can be a great option if you don’t know what lens size to buy or you will be moving the camera to various locations with different lens size requirements. These also work well if you want to zoom in on something within a short distance from the camera.
When shopping for a varifocal camera, you may see them advertised as 4X zoom, or 10X zoom or 25X or whatever. This 25X zoom camera from Hikvision has a focal length from 4.8mm – 120mm. It’s called a 25X lens because 4.8 X 25 is 120mm. 4.8 is 1X and 120 is 25x. It’s another way of wording the camera’s optical abilities in a less tech savvy manner.
There is another factor which can influence your viewing angle. The size of the sensor. I show some great examples here.
When selecting a security camera, knowing the viewing angle is more important than knowing the lens size. For me, the lens size gives a ballpark figure of wide angle or zoom. The viewing angle is an actual measurement dictating your coverage.
The exact viewing angle, gives you the exact coverage to expect.
I show an example using triganomatry and how to calculate the viewing width given the camera's viewing angle.
We do a minimal focal distance test on all the cameras and then check out how the IR lights’ hardware is impacted by the given lens size.
Tonnes of information and I hope you learn a lot!

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