This
article discusses
the interaction between shutter speed, aperture and the ISO setting
and explains the impact of changing these settings on your final
photograph.
Firstly,
it is important to note that there is an optimal exposure setting for
each photograph you wish to take. Thankfully, this is automatically
calculated by your camera (unless you are working with some very old
equipment!). You, as the photographer, however, do get the
opportunity to choose which camera settings to use at the determined
exposure.
The
exposure setting comprises 3 variables – shutter speed, aperture
and ISO. These can be summarised as:
- Shutter speed – the length of time the shutter is open while taking the photograph;
- Aperture – the amount of light which is allowed through the shutter when it is open;
- ISO – the sensitivity of the digital sensor to light hitting the sensor.
Your
camera determines the amount of light which is required to correctly
expose the particular scene. You, as the photographer, however,
should choose the settings to achieve that exposure.
Thus,
for example, the following table shows different settings, resulting
in the same exposure:
Shutter
speed - Aperture - ISO
1/125s f8 100
1/250s f5.6 100
1/15s f22 100
1/250s f8 200
Importantly,
each of the above settings would give you a perfectly exposed
photograph (in this example). However, how the photograph looks would
be different. In example 2, there would be a smaller depth-of-focus
meaning the foreground and background would be more blurred. In
example 3, there would be a larger depth-of-focus (ensuring front to
back sharpness) but the longer shutter speed would blur movement in
the picture (e.g. running water) and would likely require a tripod to
ensure a sharp end-result.
This
is where the fun really starts with photography as you can use the
different variables to create different end-results for your
photographs, depending on what you are trying to achieve as a
photographer.
You will be able to set the different
settings on your camera independently or in priority – so, say, you
know you want to use ISO 100 and an aperture of f5.6, by choosing the
Aperture priority mode and setting the ISO setting to 100, your
camera will automatically work out the correct shutter speed.
Information on how to select the particular settings should be
available in your camera manual.
You should experiment with different
settings to get an understanding of the impact on your photographs.
Hopefully
useful
