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Photography: ISO sensitivity

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Formerly known as ASA, ISO sensitivity specifies the ability of your camera's sensor to detect light. The higher the ISO setting, the more responsive the sensor will be to light and hence the less time that will be required to capture a scene, thereby letting you work with faster shutter speeds to avoid blur.

1. Values

On most cameras, ISO sensitivity is set as a whole number, where each subsequent value is double the previous value, meaning the sensor is twice as sensitive to light: 100, 200, 400, 800, 1600, 3200,etc. On some models, intermediate values (100, 125, 160, 200, etc) may be available.

  • Values up to 200 ISO are considered to be a low, while 800 ISO or above is considered to be high

2. High ISO settings

High sensitivity settings (higher than ISO 400) lead to a reduction in the sensor's dynamic range: its ability to sense subtle differences is limited. it will also tend to make dark tones appear black and make light tones appear white.

  • With SLRs: work with ISO 400, as this will allow you to use a fairly fast shutter speed without degradation of image quality. Some newer SLRs offer usable quality at up to ISO 3200 and others may even go up to record values of 102,400 ISO!
  • Compacts and bridge models: quality is degraded from 400 ISO upwards, and particularly so as you exceed this value.

3. Noise

As the ISO setting is increased, more and more noise will appear in the form of blue and green speckles either in specific areas or across the entire image. These speckles are liable to obscure fine details, thereby reducing picture quality.

  • Noise reduction is still possible using image processing software. Note: noise cannot be removed completely without degrading the actual image.
  • It is best to avoid excessively high ISO settings. Save high ISO settings for cases where you cannot use flash in low-light conditions and where a fast shutter speed is required to capture a still image of the subject.


Convert your picture to black and white, thereby turning the noise into grain, which always blends in better with monochrome pictures. Try it!