5 Fast lenses
I almost never set out to photograph a landscape, nor do I think of
my camera as a means of recording a mountain or an animal unless
I absolutely need a “record shot.” My fi rst thought is always of
light.
—Galen Rowell
Just as with sports cars, computer processing, bullet trains, and
Internet connections, being fast is great for camera lenses. It’s
much easier to take photographs in low light with an f/2.0 or
f/2.8 lens than with an f/4.5 or f/5.6 lens. Camera companies
don’t bury us with choices like the car manufacturers, usually
selling just two or three similar lenses in the same focal-length
range. We hope that this chapter will make understanding and
choosing lenses a bit easier. Some of this “glass” (slang for lens)
is very expensive, because it’s specialty stuff, absolutely needed
by pros in many situations; but as we’ll soon see, it’s not neces-
sary for everyone.
An understanding of the relationship of shutter speed to lens
aperture is necessary to understand the importance of lens
speed. Camera shutter speeds are measured in seconds and
fractions of seconds. An exposure can be six seconds long
