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I am utilizing a built in function named "getVerticalViewAngle()" to get the Vertical View Angle of Android Device Camera. The above function returns "63.8146" degrees as the Vertical Angle.

Now if I use the tablet on a tripod so that tilt is eliminated (Keeping tablet camera lens height as 900mm) and capture a picture of a wall at a distance of 1500mm, then 1800mm of the wall(vertical) is included within the picture. Calculating the Vertical Angle based on above scenario yields 61.9275 degress which is not equivalent to 63.8146.enter image description here Can anyone please explain why there is difference between Angle values?

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  • we have tried numerous times and there is always a discrepancy. @MattGrum
    – Wm_Pooja
    Apr 9, 2015 at 11:51
  • The image will have been cropped slightly by the demosaicing process, though probably not enough to account for 1.8 degrees, so either the value returned by the function is not accurate, or your measurements are not accurate, or a combination of both
    – Matt Grum
    Apr 9, 2015 at 13:32

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The angle of could be stated at infinity focus. Focal length (and thus angle of view) usually change slightly when focusing at different distances, unless you spend 5 figures on a cine lens. However normally the focal length gets shorter the closer you focus, and I can't imaging a mobile camera lens does much more than unit focusing (moving the entire lens back and forth).

The other thing to note is that the function will just be recalling a value stored in the camera firmware, it's not measuring it directly, so if the wrong value was entered or if it was measured using a different procedure or standard, then it might disagree with what you're observing.

If you measure any lens property, focal length, aperture etc. you'll find they're not exactly as stated by the manufacturer. It's possible they calculated the FOV based on the nominal focal length rather than the true focal length, or the nominal sensor size rather than the true sensor size.

At the end of the day an Android tablet is not a scientific instrument so I would expect it to be calibrated as such. The stated value is probably enough for most camera apps to work with.

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