Exposure is one of the most critical elements of Photography.
There are three adjustable elements that control the exposure:
ISO, Aperture and Shutter Speed.
The measure of a digital
sensitivity to light
(5) Shutter Speed
The amount of time that
the shutter is open
The size of the opening in
the lens when a picture is
• Controls the speed at which the shutter opens and closes
• The shutter blocks all light from exposing the film UNTIL you press the button. Then
it quickly opens and closes, giving the film a brief flash of light.
• You can control the length of time the shutter remains open by setting the
• It determines how long the shutter stays open.
• The longer exposures ( like 1 second ) give much more light to the film than a
1/1000 of a second exposure. So even though the number may look bigger, don't be
Longer shutter speeds = more light
Shorter shutter speeds = less light
WHAT SHUTTER SPEED TO USE
• A standard shutter speed is 1/125 or 1/250 of a second –
these speeds are appropriate for a normally lit outdoor
• Bright, sunny day/ excessive light – use a faster speed
• Overcast or late afternoon – a slower speed should be
used, such as 1/60
• A shutter speed slower than 1/60 of a second should only
be used with a tripod
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• Before light reaches film, it must pass through an opening
called an "Aperture".
• Like the pupil in a human eye, the aperture on a camera
controls light. It does so by closing up to restrict light, and
opening up to let it through.
Smaller F-stop number = larger opening
Larger openings = more light
• The f stop number indicates a fraction of the hole’s size in
relation to the focal length of the lens
• Each f stop allows half as much light as the f stop before it
The larger the f stop number, the smaller the hole in the lens
WHAT APERTURE TO USE
• A standard aperture is around f.8 or f.11
DEPTH OF FIELD
• The eastist way to understadn how to control the zone of
focus in a photograph is to remember the following:
• Large f stop number (for example, f.22) = large DOF
• Small f stop number (for example, f.4) = small DOF
ISO (INTERNATIONAL ORGANISATION FOR STANDARDISATION )
• Is the sensitivity of the film or imaging sensor to light
• The ISO is often referred to as ‘light speed’
• The faster the film speed, the higher the sensitivity of the
film to light
• The higher the number, the higher the degree to sensitivity
High ISO =
Poor lighting conditions (for example indoors without a flash)
SITUATIONS - ISO
Situations where you might need to push ISO to higher settings
• Indoor Sports Events – where your subject is moving fast yet
you may have limited light available.
• Concerts – also low in light and often ‘no-flash’ zones
• Art Galleries, Churches etc- many galleries have rules
against using a flash and of course being indoors are not
• Birthday Parties – blowing out the candles in a dark room can
give you a nice moody shot which would be ruined by a
bright flash. Increasing the ISO can help capture the scene.
A METAPHOR FOR EXPOSURE
Imagine your camera is like a window with shutters that open and
Aperture is the size of the window. If it’s bigger more light gets
through and the room is brighter.
Shutter Speed is the amount of time that the shutters of the window
are open. The longer you leave them open the more that comes in.
Now imagine that you’re inside the room and are wearing sunglasses
(hopefully this isn’t too much of a stretch). Your eyes become
desensitized to the light that comes in (it’s like a low ISO).
There are a number of ways of increasing the amount of light in the
room (or at least how much it seems that there is. You could increase
the time that the shutters are open (decrease shutter speed), you
could increase the size of the window (increase aperture) or you
could take off your sunglasses (make the ISO larger).
A METAPHOR FOR EXPOSURE
Achieving the correct exposure is a lot like collecting rain in a bucket.
While the rate of rainfall is uncontrollable, three factors remain under
your control: the bucket's width, the duration you leave it in the rain,
and the quantity of rain you want to collect. You just need to ensure
you don't collect too little ("underexposed"), but that you also don't
collect too much ("overexposed"). The key is that there are many
different combinations of width, time and quantity that will achieve
this. For example, for the same quantity of water, you can get away
with less time in the rain if you pick a bucket that's really wide.
Alternatively, for the same duration left in the rain, a really narrow
bucket can be used as long as you plan on getting by with less water.
In photography, the exposure settings of aperture, shutter speed and
ISO speed are analogous to the width, time and quantity discussed
above. Furthermore, just as the rate of rainfall was beyond your
control above, so too is natural light for a photographer.