84 Technical Issues: Killing the Gremlins
generally, the higher the quality of the image. Most cameras have a
base ISO of between 50 and 200. As you increase the ISO, more ampli-
fi cation is used to compensate for the reduced amount of light, leading
to noise. This can be useful. The shutter speed for correct exposure
for a given lens aperture will increase, meaning you can shoot hand-
held without visible camera shake or use smaller lens apertures for a
greater depth of fi eld. The trade-off is more noise—how much more
will depend upon the characteristics of the image sensor and (when
shooting JPEGs) the effi ciency of the camera maker’s noise-reduction
algorithms.
Your camera should have an ISO setting on a dial (Figure 5.4) or
a menu from which you can select the ISO. Some cameras will select
the ISO automatically, increasing it to prevent camera shake. Do not
be tempted to leave the choice of ISO to the camera if you are shooting
for stock. Set the ISO manually, as low as possible for the light level
you are shooting in.FIGURE 5.4 An ISO dial on a quality
compact camera. Avoid Auto and Hi (high)!
Stick to settings below 200 ISO. Not all
cameras have a separate dial for ISO settings;
some have ISO settings buried in a submenu.
© Douglas Freer