[OSM-dev] OpenStreetView: Digital Photos: Getting the field of view angle

[Vincent MEURISSE]

On Sunday 16 August 2009 14:42:26 Nick Whitelegg wrote:
> The thing I don't really know much about is: how can you get the
> field-of-view angle of a photo taken from a digital camera (either a
> standalone camera or within a phone)? 
The formula is :
Tan(angle/2)=size of film/(2*focal)

for a standard film you get and a 50mm objective:
size of film = 24x36 (diagonal=43.3)
so angles are:
vertical 27°
horizontal 39.6°
diagonal 46.8°

> I've seen a few explanations on the
> web on how you get it from the focal length (which appears to be quoted in
> e.g. the N95 specs) but they also require another parameter (the "size of
> the film"). Where might I get this from?
In fact you don't really need the size of film (captor size). Most of the 
camera store the focal in both real and equivalent distance.
If I take a random picture from a nikon D300 the exif information contain 
this:
Focal Length: 70mm
Focal Length In 35mm Film: 105mm
Digital zoom ratio: 1.0

So with the equivalent focal and the digital zoom, you can get your angle.

-- 
Vincent MEURISSE