Page 98 - (DK) Advanced Photography Guide

96 EXPLAINING | FOCAL LENGTH

FOCAL LENGTH

Measured in millimeters, focal length is the controls the angle of view and the magnification
distance from the optical center of a lens to a of subjects. The shorter it is, the wider the angle
camera’s focal plane (where light is focused) of view and the lower the magnification.
when the lens is focused on infinity (∞). Along Long-focal-length lenses have a narrower
with the size of the camera’s sensor, focal length angle of view and greater magnification.

ANGLE OF VIEW 84° 63° 43°

FULL FRAME / APS-C 24MM / 16MM 35MM / 23MM 50MM / 33MM

The sensor in a full-frame
camera is the same size as
a 35mm film frame, whereas
those in ASP-C cameras
are smaller.
When a lens is attached to
an APS-C camera, the angle
of view is narrower than it
would be on a full-frame
camera. The difference can
be calculated using the crop
factor for the sensor (see
p.98). APS-C cameras require
a shorter-focal-length lens to
match the angle of view of
an equivalent lens attached
to a full-frame camera.
Manufacturers sometimes
use the full-frame equivalent
when describing the angle of
view of a lens, rather than the
actual focal length. The angles
of view in this illustration are
measured across the diagonal
of the frame.

▶ As the focal length
increases, the angle of view
becomes narrower and the
magnification greater.

US_096-097_Understand_FocalLength1.indd 96 05/02/2018 14:35