Angle of view describes the angular extent of a scene that is captured by a camera. It is determined by the effective focal length of the lens and the image sensor dimensions. For rectilinear images, the angle of view can be calculated using trigonometric functions based on the focal length and sensor size. The effective focal length may differ from the stated focal length for macro photography, where the object distance is close to the focal length.

1. Angle of view
In photography, angle of view describes the angular extent of a given scene that is imaged
by a camera. It is used interchangeably with the more general term field of view.
It is important to distinguish the angle of view from the angle of coverage, which describes
the angle range that a lens can image. Typically the image circle produced by a lens is large
enough to cover the film or sensor completely, possibly including some vignetting toward
the edge. If the angle of coverage of the lens does not fill the sensor, the image circle will be
visible, typically with strong vignetting toward the edge, and the effective angle of view will
be limited to the angle of coverage.
A camera's angle of view can be measured horizontally, vertically, or diagonally.
Calculating a camera's angle of view
For lenses projecting rectilinear (non-spatially-distorted) images of distant objects, the
effective focal length and the image format dimensions completely define the angle of view.
Calculations for lenses producing non-rectilinear images are much more complex and in the
end not very useful in most practical applications. (In the case of a lens with distortion, e.g.,
a fisheye lens, a longer lens with distortion can have a wider angle of view than a shorter
lens with low distortion) Angle of view may be measured horizontally (from the left to right

2. edge of the frame), vertically (from the top to bottom of the frame), or diagonally (from one
corner of the frame to its opposite corner).
For a lens projecting a rectilinear image, the angle of view (α) can be calculated from the
chosen dimension (d), and effective focal length (f) as follows:
alpha = 2 arctan frac {d} {2 f}
d represents the size of the film (or sensor) in the direction measured. For example, for film
that is 36 mm wide, d = 36 mm would be used to obtain the horizontal angle of view.
Because this is a trigonometric function, the angle of view does not vary quite linearly with
the reciprocal of the focal length. However, except for wide-angle lenses, it is reasonable to
approximate alphaapprox frac{d}{f} radians or frac{180d}{pi f} degrees.
The effective focal length is nearly equal to the stated focal length of the lens (F), except in
macro photography where the lens-to-object distance is comparable to the focal length. In
this case, the magnification factor (m) must be taken into account:
f = F cdot ( 1 + m )
(In photography m is usually defined to be positive, despite the inverted image.) For
example, with a magnification ratio of 1:2, we find f = 1.5 cdot F and thus the angle of view
is reduced by 33% compared to focusing on a distant object with the same lens.
A second effect which comes into play in macro photography is lens asymmetry (an
asymmetric lens is a lens where the aperture appears to have different dimensions when
viewed from the front and from the back). The lens asymmetry causes an offset between
the nodal plane and pupil positions. The effect can be quantified using the ratio (P) between
apparent exit pupil diameter and entrance pupil diameter. The full formula for angle of view
now becomes:
alpha = 2 arctan frac {d} {2 Fcdot ( 1 + m/P )}
Angle of view can also be determined using FOV tables or paper or software lens calculators.