Human sight can perceive a much
wider range of light intensities than a
digital camera sensor. We can look
through a window and still see what
is inside at the same time, even
though the light conditions inside are
totally different from these outdoors.
Cameras, and especially digital
cameras, cannot. So on camera, you
will only see what's outside through
the window or what's inside.
Steady your camera
If you have a tripod, use one; if you
have a solid surface to rest on, then
do so. Not that a tripod is as
necessary as many people say it is;
but to observe the effects of
various camera settings, it's best if
you get several shots of exactly the
same thing. Tripods really come in
handy for slower shutter speeds.
Most pictures go bad because of a
camera shake. Though as
mentioned above, if your lens has
an automatic stabiliser, use it....
Play with your camera's ISO speed.
The ISO speed is a measure
of your camera's sensor's
sensitivity to light; a lower
number is less sensitive,
and a higher number is
more sensitive. Take a
photo of your subject at its
lowest ISO speed (or
"slowest", typically 50, 100
or 200), and then take one
at its highest (800, 1600 or
more).
Set your lens' aperture (also
called the diaphragm).
This might be a dial on your lens with a
series of numbers on it (which will
typically fall anywhere between around
1.4 and 22 on most lenses); otherwise,
refer to your camera's instructions. The
diaphragm is just that: a opening
towards the front of your lens that lets
more or less light onto the sensor. The
size of the diaphragm is expressed as a
ratio of focal length to aperture size
(hence, they are referred to as, for
example, f/5.6); consequently, a smaller
aperture (less light onto your sensor) is
expressed by a larger number. So, take
two photographs, one with a larger
aperture, and then stop down and take
one with a smaller aperture.
Manual
This will tell the camera to
give up all control of trying to
expose your picture properly.
Most of the time, you will not
need to use this (and
shouldn't; exposure control
exists for a reason). But we'll
need to do this if we're going
to show the effects of shutter
speed.
Shutter speed
See your manual for the exact details
of how to do this. Shutter speeds are
numbers which go up in a sequence
that roughly doubles each time, and
normally expressed as a fraction of a
second; i.e. 1 second, 1/2, 1/4, 1/16,
1/25, and so on (each one usually being
called a "stop"). Take two pictures at
shutter speeds a couple of stops apart
Lens
50mm
How human see
28mm
Wide angle
80mm
Telephoto
Flash
SLRs generally can automatically control output of
their internal flash, or an external flash with much
higher maximum power, to provide even light
across a subject. Use a flash at reduced power
(applying negative "flash exposure compensation")
in sunlight to soften but not eliminate
shape-defining shadows. Use a flash in dim light to
light the scene. Bouncing a flash off the ceiling (with
an external unit with a hinged head) will softly light
a large area. A slower shutter speed makes the
scene's ambient light more conspicuous but don't
use such a slow shutter speed that the ambient
light can blur the scene due to camera shake or
subject movement over a long exposure.