Exposure is the amount of light collected by the
sensor in your camera during a single picture.
If the shot is exposed too long the photograph will
be washed out. If the shot is exposed too
short the photograph will appear too dark.
Almost all cameras today have light meters which
measure the light in the given shot and set an ideal
exposure automatically. Most people depend on
the light meter which is fine, but if you know
how to control your exposures you can get some
creative and sometimes better pictures. (The
photo on the left is with low shutter speed and
narrow aperture (high f/stop).
The two primary controls your camera uses for
exposure are shutter speed
(the amount of time the sensor is exposed to light) and aperture (the
size of the lens opening that lets light into the camera). Shutter
speeds are measured in seconds and more commonly fractions of a second.
(1/2000 of a second is very fast and 8' seconds is extremely slow).
Apertures are measured in something called f/stops (a very wide aperture is
f/2.8 and a very small aperture is f/19).
You might wonder why there is not just a constant
shutter speed or a constant aperture so that you
would only have to worry about one control.
The reason is that even though they both control the
amount of light getting to the sensor they also
control other aspects of the picture. Shutter
speed for example can be used to freeze subjects in
midair with a fast speed or it can be used to blur
water with a slow speed. Aperture controls the
depth-of-field which is what is in focus in the
picture. Aperture can be used to draw
attention to one subject (like the flower on the
right) by blurring the background with a wide
aperture (low f/stop). Aperture can also be
used to focus everything in a picture with a narrow
aperture (high f/stop). (The photo on the left
is with Wide aperture (low f/stop) and corresponding
shutter speed).
On most digital SLR's (Single Lens Reflex) cameras today you can even change the
sensitivity of the sensor when collecting light which is called the ISO
speed. The common span of ISO speed is 100 to 800. The higher
the ISO speed the faster the camera collects light but it also adds more
noise to the photograph than the lower speeds. For example if your
trying to take pictures in dim light without a tripod you might want to
raise the ISO speed in order to get a picture that's not blurry. Most
of the time you should keep it at a lower ISO speed if there is enough light, but it makes
a big difference when there isn't.
Low shutter speed and slightly narrow
aperture (pretty high f/stop)
The best way to learn how to use shutter speed and
aperture is to just keep experimenting with them.
Exposure is the amount of light collected by the
sensor in your camera during a single picture.
If the shot is exposed too long the photograph will
be washed out. If the shot is exposed too
short the photograph will appear too dark.
Almost all cameras today have light meters which
measure the light in the given shot and set an ideal
exposure automatically. Most people depend on
the light meter which is fine, but if you know
how to control your exposures you can get some
creative and sometimes better pictures. (The
photo on the left is with low shutter speed and
narrow aperture (high f/stop).
You might wonder why there is not just a constant
shutter speed or a constant aperture so that you
would only have to worry about one control.
The reason is that even though they both control the
amount of light getting to the sensor they also
control other aspects of the picture. Shutter
speed for example can be used to freeze subjects in
midair with a fast speed or it can be used to blur
water with a slow speed. Aperture controls the
depth-of-field which is what is in focus in the
picture. Aperture can be used to draw
attention to one subject (like the flower on the
right) by blurring the background with a wide
aperture (low f/stop). Aperture can also be
used to focus everything in a picture with a narrow
aperture (high f/stop). (The photo on the left
is with Wide aperture (low f/stop) and corresponding
shutter speed).
