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Sensitivity or ISO is referred to the
ability of the sensor picking up the light hitting on it. For
conventional film camera, it is depend on the film. For film camera, in
order to change the ISO, user will need to change the film, whereas in
digital camera, ISO setting can be change easily by a press of button.
In film camera, lower ISO film means it
need more light for sufficient exposure and it produces photo with
finer grain. However for film with higher ISO rating, then lesser light
is needed for sufficient exposure, but the photos will be grainier.
Same theory applies to the DSLR nowadays. With lower ISO, more light is
needed by the sensor and the photo produced is lesser noise. However
for higher ISO, less light is needed but the photo will create more
noise.
Coincidentally, both got the same outcome, less ISO will need more
light and produce better photo, high ISO will need lesser light but
suffered grainy output in film camera and higher noise in digital
camera. For digital camera, when ISO is higher, less light is needed as
it is amplified at the sensor. However, the noise is amplified together
and causing a noisy output.
Example of photo with ISO100
Example of photo with ISO3200
Noticed the noise resulted in the photos with ISO3200 compare to the
other one with ISO100. The noise that is produce has blurred the water
drops on the tomatoes and the texture of the table that it is sitting
at.
The normal ISO setting is as below,
ISO50, ISO100, ISO200, ISO400, ISO800, ISO1600, ISO3200
The difference between the ISO settings is 1 EV. For example the
sensitivity of ISO 200 is twice as much as ISO 100 and sensitivity of
ISO 800 is twice as much as ISO 400. Similar to aperture and shutter
speed setting, the different between each ISO setting is consider as
one stop. For example, ISO200 is one stop higher than ISO100.
As discussed in how the exposure value works, ISO setting is take into
consideration when we change it to achieve sufficient exposure.
For example: F4, 1/30s, ISO800 = F2, 1/30s, ISO200
Both will gives the same exposure level, as the aperture size goes up
two stop and ISO dropped two stop.
Controlling the ISO setting enables us to take photos in low light
environment. However, increasing the ISO setting gives us a pain in the
back - the increase of noise in the photos. Hence for photographers
that seek quality photos, they tend to use lower ISO setting together
with tripods.
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