Lens Angle Spec'd Differs From Lens Angle Calculator?

Recently, Carl noted that the lens angle specified in Axis M30 series cameras differed from what he calculated using a lens calculator. We verified this with a second calculator.

Here's what's in the spec:

Here was Carl's response, using a lens calculator:

  • A 2.8mm lens theoretically gives a 65 degree HFOV on a 1/4" sensor (M3004). [vs 80 degrees listed]
  • 2.8mm should give approximately 85 degree HFOV on a 1/2.7" sensor (M3005). [vs 118 degrees listed]
  • 1.6mm should give approximately 100-110 degree HFOV on a 1/3.6mm sensor (M3006). [vs 134 degrees listed]
  • My lens calculator doesn't go as low as 1.3mm, so I can't comment on the M3007.

On 3 of the lenses, the angle listed on the spec was notably wider than what the lens calculator reported.

Here is Axis' response:

"We measure the actual FOV for the cameras before stating the angles in the datasheet. As you know the FOV depends on the focal length of the lens, the sensor size, resolution, etc. Additionally any barrel distortion of the lens and can also come into play. We are working on a white paper explaining barrel distortion as it relates to wide angle lenses and other potential artifacts."

We also asked about the M10 series where two cameras had the same imager size and lens focal length but different lens angle. They responded:

"It's dependent upon how we use ‘scan’ the sensor. We don’t necessarily use all of the sensor with all products."

Let me know if anyone has any feedback or thoughts. I'll update this with Axis's white paper when it is released.

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