Compare this to the water
bucket scenario. You have a 1 gallon bucket (compare to
film sensitivity) that you have to fill in 2 minutes.
You open your faucet to 1/4 open (aperture) and let the
water flow for 2 minutes (shutter speed) but the bucket
is only half full at the end of 2 minutes
(underexposed). So to fill the bucket you have to change
one of the variables. Either the faucet opening
(aperture) or the time of water flow (shutter speed).
Since we said that you had to fill the bucket in 2
minutes you will have to change the faucet opening
(aperture). We need twice as much water in the same
amount of time so we open the faucet to 1/2.
Hopefully you have been
able to follow along and I have not made to confusing so
Things to consider when setting
your exposure controls.
When you change your
aperture or your shutter speed you are changing 2
qualities of the image other then proper exposure, Depth
of field (aperture controlled) and motion blur (shutter
With larger aperture
settings (smaller numbers) you get less depth of field
or less area in sharp focus. Therefore f2.8 would have
less area in sharp focus then f5.6. I have a related
article on this site about selective focus you should
read for a better understanding.
Click here to read it.
With shutter speed you
control how much motion blur there is in your image. By
selecting the proper shutter speed you can pan the
camera with a moving car to get a sharp car in the image
and everything else would be blurred by motion or you
could stop a tennis ball as it crosses the net by using
a fast enough shutter speed. One thing to remember about
shutter speed is that I believe camera shake ruins more
pictures then anything else. This comes from hand
holding a camera at too slow of a shutter speed. As a
rule of thumb, never hand hold a camera at a slower
shutter speed then the reciprocal of the length of the
lens. In other words, if your using a 100mm lens then
never hand hold your camera at a shutter speed slower
then 1/100 of a second. Use a tripod.
Now take these
considerations and go out and practice using them. It
doesn't matter what you photography, just do it at
different settings and study the results.