Many cameras have more stops at either end of these scales, but these
are typical. As well, most modern cameras have half stops or third
stops. These make learning a little more difficult, but keep the above
numbers in mind to do proper exposures.Note: Completing this lesson requires a camera capable of manually setting exposure.
What is the right exposure? Not to make this
complicated, but exposure is a choice you have to make. The exposure you
choose determines how the image looks. But, we’ll start with a basic
understanding and work up from there.
Exposure consists of four factors:
- how much light is in front of you – which can be changed by adding lights or flash,
- how sensitive the film is to light – called ISO
(remember, I use the word “film” to refer to whatever medium used for
capturing the image, whether it is the Digital Camera’s sensor or
actually film,)
- the amount of light going through a lens – called the aperture,
- how long the film is exposed – called the shutter speed.
For a little more about how this works see the
Camera Basics Page.
For the moment, we’ll set an average exposure on an average scene.
If you’re camera does not have a built in meter – its really old.
But, that’s okay. You’ll just have to buy a hand held meter. If you have
an SLR or advanced point and shoot digital camera, spend some time with
the manual to find out how to bring up the “Histogram” which
graphically shows the amount of light in an exposure.
First exercise – set your ISO to 100, set your
camera to ƒ16 and the shutter to 1/125th of a second. (Some digital
cameras are limited to ISO 200 – which means you have to cut your
exposure by one stop, i.e. use 1/250th instead of 1/125th of a second)
With this setting, take your camera out during a sunny day, put the sun
behind you and shoot anything – you’ll have a well exposed image.
This is called the “Sunny 16″ rule.
To make life interesting, and your photography more creative, you can
change the setting and still have the same exposure. These are
equivalent exposures: Try going to ƒ11 at 1/250th of a second. Push it a
little further at ƒ8 at 1/500th of a second. These are all the same
exposure because the same total amount of light is hitting the film.
Of course, you’re not always going to shoot with the sun behind you
on a sunny day. For other situations you need to be able to find out
your exposure with a meter. This can be in your camera or hand held.
Looking at any scene, your meter will give you a suggestion as to
what exposure to use. Most of the time this is fairly accurate.
Using your meter, take a reading off of something with mixed tones in
shade on a sunny day – you’ll find the exposure is two or three stops
slower than the “Sunny 16.”
Second exercise
One of the best things to do for more accurate exposure is to meter
the light hitting the specific subject you’re shooting. Find a place
where there is a small patch of light such as a break in a wall, light
coming directly through a window, etc. Take a picture from far enough
back you get lots of the shadow area. You’ll probably find the patch of
light is way too bright in the picture. Walk right up to the patch of
light and see what the meter suggests you use there. Then, go back to
where you’re taking the picture from – and with the camera in manual –
set the exposure to what was suggested.
You can also use your hand to help determine exposure in a variety of
situations. First – on a sunny day, do the f16 rule, setting the camera
to f16 at 1/125 of a second. Hold your hand in the sunlight and meter
it. You’ll probably notice the meter says you should change the
exposure. Note how much the meter says your hand is off from the f16
rule and keep that in mind. Lets say the meter said you should expose
your hand at f22. That is one stop darker than what is actually needed.
Now walk into the shade and meter off your hand again. If it says f11,
you know that is one stop too dark, so set your camera to f8.
Knowing what your hand is for exposure can help you set exposure in
most situations – just make sure your hand is in the same kind of light
as the subject you’re shooting.
A little more accurate way to do exposures is to buy an “18 per cent
grey card.” Most camera stores and photo departments should have these.
To use it, just put it beside the subject you’re shooting, and meter off
of it. If you’re further away than is practical to walk up to the
subject – set the card in the same kind of light as the subject and
again meter off the card.
Third exercise – either with an 18 per cent grey
card, or using your hand as described above, meter something in dark
shade and find out the exposure there.
A final note – A meter is very handy for getting
your exposure, but it does have a limitation. As said earlier, the meter
thinks the world is 18 per cent grey. Most of the world is kind of like
18 per cent grey, but not all of it.
Look at what you’re shooting. If its black (or very dark), your meter
will try to make it grey – and make the exposure too light. Conversely,
if you’re subject is white, the meter will try to make it darker – or
18 per cent grey.
There are two more lessons on high key and low key photos which will help you handle more extreme situations.
Note: Be aware that some digital cameras have
exposure compensation built in to prevent overexposure. If exposure is
too bright the highlights could be “blown out” and detail lost in the
brightest parts of the image. By artificially “darkening” the image, the
camera makers try to make sure the exposures aren’t too bright. This
doesn’t affect all cameras but it does seem to be the case for some.
That means that the exposure needed in lessons 2, 3 and 4 may be
slightly higher than suggested in the lessons. You might use the “expose
to the right” method.