you have AV mode turned
on, you can change the f-number by rotating
the main dial above the shutter button.
Note: this is for Canon
digital cameras. You may need to refer
to your manual to find out how to change
the F stop for your specific
brand of camera.
the f number is small, the lens diaphragm
is actually wide open. So if someone says
to you that you need to open your lens
more, they mean to lower the aperture
or F number. Alternatively, if the aperture
is a large number, say F22 then the lens
diaphragm is smaller or more closed. This
often causes much confusion with beginners.
your lens more refers to lowering the
• Closing your lens more refers
to a higher f number.
best way to understand how aperture works
is to take numerous photographs with different
f-number values and see what the difference
images at both ends of the scale. One
with as low a F number as possible and
one with as high a F number as possible.
More importantly, when you view them on
your computer take notice of how much
of the photo is in focus.
below is a couple of examples I've done
myself to help explain aperture.
the first photograph shown below, the
aperture (f number) was set at f/11 so
all the image is in focus.
for the second photo, the aperture was
set at a smaller number f/5.6 so only
the rocks and sand at the foreground are
in sharp focus while the background elements
here is an example of a close object photographed
with an aperture value of f/5.6. As you
can see the foreground object is in sharp
focus and the background is blurry.
also important to note that results from
aperture settings can change from one
lens to another. For example just because
an aperture value of f/5.6 for your macro
lens results in a blurred background,
it doesn't mean you should also set your
telephoto or wide angle lens to the same
f stop. Therefore its important to experiment
with all your camera lenses so you know
your equipment better.
photographs shown on this page are taken
with a Canon 400D (Rebel XTi) Digital