23. SENSOR SENSITIVITY
• The ISO value is a measurement of the
cameras film/sensors sensitivity to light
• The lower the number (e.g. 100) the more
light that is needed but the better the quality
• The higher the number (e.g. 400) the less light
that is needed but the poorer the quality
• ADVICE – use the lowest ISO value that you
can !
24. SHUTTER SPEED
• The relationship between shutter speed and aperture is
fundamental to the understanding of exposure and
photography on the whole. While the latter primarily
controls depth of field, the former can transform images
with presence of blurred motion or, at the other extreme,
freeze an instant of time by thousandths of second.
• The term ‘shutter speed' refers directly to how long the
shutter within your camera remains open, and therefore
how much light is able to reach the sensor. Shutter speeds
are measured in seconds and fractions of seconds - the
longer the shutter remains open at a set aperture, the
more light will reach your camera's sensor, and vice versa.
25. • When looking to keep images sharp, a good
general rule of thumb is thus - the maximum
shutter speed you can use is 1/ your focal
length. For example, take a focal length of
50mm - the longest shutter speed from which
you can expect a sharp image is 1/50 second.
Image stabilisation goes some way to
extending this, but it's best not to rely on this
if razor-sharp images are needed.
