■ Focus. Focus by hand or use autofocus.
■ Special lenses. Use special lenses for close-ups, panoramas, and other spe-
cial images.Carpenters must know their tools to stay in business. The same can be said for pro-
fessional photographers. Besides your creativity, nothing influences the quality of
your imagery more than the lens. Studying the characteristics of lenses will make
you a better photographer.Lens Focal Length
The most significant difference among lenses is their focal length. A lens is often
described in terms of its focal length (such as a 50mm lens) or its physical length
(short, medium, long). Technically, focal lengthis the distance between the lens’s rear
nodal point and the focal plane when the lens is focused on infinity (a far distance
from which light reaches the lens in more or less parallel rays).
The focal length controls magnification, or the size of the image formed by the lens.
The longer the lens, you will find the size of objects in the image greater. A lens of
longer focal length bends light rays less than a short lens does (see Figure 4.1). The
longer the focal length, the less the rays are bent, the farther behind the lens the
image is focused, and the more the image is magnified (see Figure 4.2). The size of
the image increases in proportion to the focal length. If the subject remains at the
same distance from the lens, the image formed by a 50mm lens will be twice as big
as that from a 25mm lens.46 ABSOLUTE BEGINNER’S GUIDE TODIGITAL PHOTOGRAPHY
FIGURE 4.1
A lens of short
focal length
bends light
sharply.Focal length 25mmFocalPlane