# Field of View

The **field of view** of a photograph or camera is a measure of the proportion of a scene included in the image. A typical fixed lens camera might have a field of view of 50�, a fisheye lens can have a field of view greater than 180� and a full equirectangular or cylindrical panorama would have a field of view of 360�.

Field of view is often abbreviated as **FoV**, it is also known as **angle of coverage** or **angle of view**.
Usually **field of view** refers to **horizontal field of view** (HFoV), some applications make use of the **vertical field of view** (VFoV) which can be calculated from the Aspect Ratio of the image:

Aspect Ratio = sin (HFoV / 2) / sin (VFoV / 2)

## Conversion from focal length

The other standard measure of the *width* or *narrowness* of a lens is Focal Length.

Assuming a 35mm negative width and a rectilinear lens, the field of view can be calculated like so:

Field of View = 2 x atan ( 35 / ( 2 x Focal Length ) )

## Conversion from horizontal to vertical and vice versa

For fisheye and equirectangular images:

vfov = height / width * hfov hfov = width / height * vfov

For rectilinear images:

vfov = 2 * atan( tan(hfov/2) * height/width) hfov = 2 * atan( tan(vfov/2) * width/height)