Computed FOV (angle of view) doesn't match the specificatoins

[MAbdo2]

I have two questions, as follows:

1) The reported intrinsic structure returns 1280 (Width) and 800 (Height) for the sensor resolution. Yet, the image has a 1280 x 720 pixel resolution. Why the discrepancy?

2) The computed FOV angles (from the intrinsic parameters) dont match closely the values given in the datasheet. My calculation is shown below. Is it normal to see so much variation between the actual and nominal (datasheet) FOV values?

With my D435 unit, the reported intrinsic parameters are shown below:

fx = 443.17

fy = 643.17

Height = 800

Width = 1280

I calculate the FOV (angle of view) as shown below:

FOV_AlongX = 2 * atan(Width / (2 * fx)) = 2 * atan(1280/(2 * 643.17)) = 89.72 (degrees)

FOV_AlongY = 2 * atan(Height / (2 * fy)) = 2 * atan(800/(2 * 643.17)) = 63.76 (degrees)

The FOV_AlongY comes to 58 degrees if I use 720 for the height instead of the reported value of 800.

The datasheet for the D435 indicates that the FOV values are 85.2 and 58 degrees.

[MartyG · Accepted solution]

The Projection section of the 400 Series documentation covers intrinsic values, including FOV. It states that "The field of view of an image may vary".

https://github.com/IntelRealSense/librealsense/wiki/Projection-in-RealSense-SDK-2.0# intrinsic-camera-parameters Projection in RealSense SDK 2.0 · IntelRealSense/librealsense Wiki · GitHub