# Calculate Angle of View from EXIF Tags



## isovist (Jul 7, 2008)

Would anyone happen to know how to calculate the "Angle of View" based on the information given in EXIF tags?

I have found several links on the internet e.g. on Wikipedia, online calculators but they are not exactly related to EIXF tags.


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## Steph (Jul 7, 2008)

First of all the angle of view will depend on the size of the sensor in your camera? We need to know that to be able to calculate the angle of view for any given focal length? What's your camera?

Edit: here is a general formula to calculate the diagonal field of view (FOV)

FOV = 2*arctan((SQRT(a*a + b*b)/2)/f)

Where SQRT = square root
         a = lenght of sensor in mm
         b = width of sensor in mm
         f = focal length in mm


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## isovist (Jul 7, 2008)

Many thanks for the response.

I am trying to build a small web-based tool to calculate the Angle of View of photos so the solution has to be a generic one and based on EXIF tags. 
I know that there EXIF tags such as image width, image height, digital Zoom Ratio,f Number, focal length, focal length in 35 mm, focal plane unit, focal Plane X Res, focal plane Y Res, res Uni, x Res, and y Res.

At the moment, I compute the AOV as follows:

AOV = 2 * arctan ((43.27/2) / (focal length in 35 mm))

43.27 is the length of the diagonal of 24 x 36 mm dimension of 35mm frame.

Is this correct? 

Are there other ways of calculating AOV for instance when the the focal length in 35 mm value is not given?


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## Steph (Jul 7, 2008)

isovist said:


> Are there other ways of calculating AOV for instance when the the focal length in 35 mm value is not given?


 
The formula I gave above will work for any format and any focal length. You just need to know the height and width of the image and the true focal length (NOT 35mm equivalent).

The formula you are using (AOV = 2 * arctan ((43.27/2) / (focal length in 35 mm)) is only valid for a 24x36mm frame (or full frame sensor).


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## isovist (Jul 7, 2008)

I agree but that's why the eqn. uses the 24x36mm size for the frame. 35mm focal length essentially indicates the lens's focal length in terms of what would be the equivalent for the conventional 35mm (film?) camera.

Bu I should compare the values.

Would the Image Width/Height substitute for the values of a and b in your eqns.?


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## Steph (Jul 8, 2008)

isovist said:


> Would the Image Width/Height substitute for the values of a and b in your eqns.?


 
Yes.


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