Graphics Programs Reference
In-Depth Information
Lens Focal Length
Focal length determines the magnification of the image converging on the
camera sensor. A lens with a long focal length magnifies the image as compared
to a lens with a short focal length. Focal length is measured from the center of
the outer lens to the light sensor and is typically measured in millimeters (see
Figure 1.10).
Lens focal langth
FIGURe 1.10
Focal length is measured from the outer lens to the light sensor.
The interaction of a lens's focal length with the camera's sensor size deter-
mines the angle of view. The angle of view approximating human vision is 50.
On a full-frame DSLR, this angle of view corresponds to a “normal” lens with a
43 mm focal length.
Lenses with angles of view wider than 60 are called wide-angle lenses. They
have correspondingly smaller focal lengths. Wide-angle lenses are useful in
enclosed spaces such as building interiors because the wide angle of view cap-
tures more of the space. However, extreme wide-angle lenses such as fisheyes
introduce a large amount of geometric distortion.
