Beginning Photography – ISO (Sensitivity)

ISO is simply the level of sensitivity to light.

In conventional film cameras, the film rolls had different ISO ratings. The rolls for general use had ISO 100 rating, those for use in low-light conditions had ISO 400 rating and so on. This means that ISO 400 films were more sensitive towards light and so, could give better results in low light shooting as compared to ISO 100 films.

Now replace the films used in conventional film cameras with the sensor used in digital cameras. As you increase the ISO, sensor becomes more sensitive to light and vice versa. Many P&S (Point & Shoot) cameras and all DSLRs allow the user to change ISO setting when taking a photograph. The ISO range is typically ISO 100 to ISO 1600 but expensive high-end DSLR may provide setting as low as ISO 50 and as high as ISO 3200.



So what happens when you increase the ISO? When you increase the ISO, output of the sensor is amplified and so less light is needed. But unfortunately that also amplifies the unwanted noise. This results in more grainy pics. This is similar to listening to music. Sometimes with music you hear some hissing sound from the speakers. Increase the volume and music becomes louder and so does the hissing sound (noise).

As mentioned earlier, ISO 100 is the normal setting for most digital cameras.