# What is mFT FoV?

Started Jan 27, 2013 | Questions thread
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 Re: practical measurement with 20mm In reply to Anders W, Jan 28, 2013

Anders W wrote:

Vlad S wrote:horizontal field of view: 19 7/32 in - 3 7/32 in = 16 7/32 in = 16.21875 in.

19 7/32 - 3 7/32 = 16 as far as I know

A typo. It's rather 19 7/16 instead. The pic shows it. I hate the fractions that the imperial tapes use. Only unnecessary complications for math.

diagonal field of view: 16.21875 / 4 * 5 = 20.2734375 in.

Diagonal angle of view: 2 * arctan (20.2734375 / 2 / 20) = 53.7550599 degrees

I suppose 20 in this formula corresponds to the distance from the sensor plane to the horizontal measuring tape. But that's not what you want for the formula to work. You want the distance from the principal plane of the lens to the measuring tape.

Sure. But a I am already satisfied with 6.7% accuracy, and I would rather spend the time on figuring out the lighting for my next project, instead of figuring out how many inches I can fit in the frame to the first decimal.