Term of the Moment

drill down


Look Up Another Term


Definition: focal length


Focal length is the optical distance in millimeters between a camera lens and the sensor or film. It determines the height and width of the scene being captured, known as the "field of view."

A prime lens has one focal length and a fixed field of view. In order to change it, the photographer has to move closer or farther from the subject. A zoom lens has a range from wide angle (35mm or less) to telephoto (60mm or greater).

Focal length is one of the two primary measurements of a camera lens. The other is the "aperture," which is the lens opening (see f-stop).






The Field of View
These photos were taken with an 18-70mm zoom lens on a digital SLR (see DSLR). At 18mm (top), the field of view is the greatest (wide angle). At 70mm (bottom), the scene is the narrowest (telephoto). This lens is equivalent to a 27-105mm lens on a 35mm SLR camera (see crop factor).






Multiple Focal Lengths on Smartphones
Smartphone lenses with different focal lengths such as these Samsung Galaxy S examples produce superior results. As smartphones advance, their cameras increasingly employ multiple lenses for better photos. See smartphone camera.





A
B
C
D
E
F
G
H
I
J
K
L
M
N
O
P
Q
R
S
T
U
V
W
X
Y
Z
misc