Graphics Reference
In-Depth Information
adjusted. This is done through setting the sensitivity rating known as the
International Standards Organization (ISO) number, and in this way it reflects
the capabilities of a range of different film stocks.
The range of settings is commonly between 200 and 800 ISO, with the higher
numbers representing the greater sensitivity and faster film speed. The
lower numbers represent less sensitivity and slower film speeds. There are
advantages and disadvantages to both fast and slow film speeds as well as
high and low ISO ratings.
Fast film, because it reacts more quickly to light, allows for very high shutter
speeds, which make it rather more suited to capturing fast action such as
sports events or animals in motion. In this way you can ensure that the
moving image is recorded sharply in focus. The other advantage of high-
speed film or high ISO numbers is that they are suited for low-light conditions,
enabling shutter speeds fast enough to capture action where lower film
speeds would require such slow shutter speeds that image sharpness would
be more difficult to achieve. However, there are downsides to high film
speeds and high ISO ratings. The higher sensitivity of photographic film is
due to the coarseness of the grains in the film emulsion. This then results in
grainier images. Likewise, digital images taken with a high ISO setting have
a higher level of digital “noise,” which looks rather like the grain in film stock.
The lower the ISO number and the slower the film speed, the finer the detail
of the final image.
Lower ISO settings may result in much finer detail in the resulting
image, but the cost of achieving this higher detail is a less sensitive CCD
that then requires slower shutter speeds to achieve correct exposures.
This makes it rather more difficult to capture fast action and at very
slow shutter speeds makes the whole process more vulnerable to camera
shake.
Lower ISO numbers around 200 result in crisper images; higher ISO ratings,
up to 800 or more, generate higher levels of digital noise, making them grainy
and less clear. This choice is the kind of compromise that you need to assess in
each situation.
You will probably find that the quality of the image needed for action analysis
can be kept to a reasonably low level. As long as the images are clear enough
for your research purposes, there should be no need to take the level of care
generally desired for high-quality prints.
Technical Issues
You need to take into account a number of technical considerations when
you choose photography as a medium for capturing action. However,
these considerations don't need to be restrictive or become an overriding
issue. Your images don't need to be works of art for them to make analysis
