Black and White Photography

5 The Shutter


Cameras usually contain a shutter, a curtain (or set of blades) that blocks light
from entering and striking the film. To take a picture, you press the shutter
button, usually located on the top right of the camera. The shutter then opens
and closes. Note that in some cameras the shutter is contained in the lens, not
in the camera body.
On all but the very simplest cameras, the amount of time the shutter stays
open is variable, an interval called the shutter speed. Most cameras either allow
you to adjust the shutter speed or do it for you. With manual cameras, you
must always choose the shutter speed yourself.
The shutter affects how the final image is rendered in two ways. It controls
exposure (how long light is allowed to strike the film) and it determines the
appearance of motion or movement (whether a moving subject looks sharp or
blurred).
The amount of time the shutter remains open is as critical to correct film exposure
as the size of the lens opening. After all, light traveling though the lens
doesn’t reach the film until the shutter opens. Thus, exposure is controlled by
two key variables: the amount of time the shutter stays open and the size of the
lens opening.
The correct shutter speed setting is determined first of all by the prevailing
light conditions. You have to select a shutter speed that lets in the right amount
of light; too much or too little light can affect overall image quality. In low
light, you will usually need a long (also called slow) shutter speed; the shutter
must remain open for a long enough interval to allow what light there is to
reach the film. In bright light, you will usually need a short (fast) shutter speed
to prevent too much light from reaching the film.
You generally make your shutter speed choice by rotating a dial located on
the camera body, often on top. With manual cameras, choosing the shutter
speed is as simple as rotating the dial to a mark that indicates the desired speed
setting. Some automatic cameras show the selected shutter speed in an LCD
display screen located on the camera. To change the setting you usually turn a
control wheel, located on the camera’s top or back. Rotate it with your thumb

or forefinger until the screen displays the desired shutter speed. Many cameras,
both manual and automatic, display the chosen shutter speed in their viewfinders
as well, so you can check the settings without moving your eye away from
the camera.
Virtually all cameras offer these shutter speed choices, in fractions of a
second from slow to fast:
1/2, 1/4, 1/8, 1/15, 1/30, 1/60, 1/125, 1/250, 1/500, 1/1000
These are generally represented as whole numbers, dropping the fractional
1/– for simplicity. Thus, 1/250 is indicated as “250” and 1/2 as “2,” and so
forth.
Many new cameras offer shutter speeds that are faster than 1/1000, such as
1/2000, 1/4000, and 1/8000, while older models may only go as fast as 1/250
or 1/500. Point-and-shoots and medium- and large-format cameras often have
a relatively slow maximum shutter speed, such as 1/500.
You also may choose shutter speeds that are a full second or longer. Most
cameras offer 1 second, represented as “1” on the camera dial or display, and
some models offer settings as long as 2, 4, 8, or more seconds. On some
cameras, the full-second shutter speeds are distinguished from the fractional
shutter speeds by color. For example, 1/2 of a second may be shown as a black
“2” and 2 seconds may be shown as a red “2.” Or, in your camera’s display,
full seconds may have a mark (such as ") after them: 4" means 4 seconds,
rather than 1/4. Consult your camera manual for specifics.
The relationship between shutter speeds is essential to understanding film
exposure. The list above indicates full shutter speeds; each full, also called
whole, shutter speed is double the time of the setting before it and half the time
of the setting after it. Thus, “4” (1/4 of a second) represents half as much time