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What is ISO?

In film photography ISO was the indication of how sensitive a film was to light and measured in numbers such as 100, 200, 400, 800 etc. The lower the ISO number, the lower the sensitivity of the film and the finer the grain in the shots taken.

In Digital Photography ISO measures the sensitivity of the image sensor. The same principles apply as in film photography; the lower the number the less sensitive your camera is to light and the finer the grain. Higher ISO settings can be used in darker situations to get faster shutter speeds however the cost is noisier shots.

Tip1: 100 ISO is generally accepted as ‘normal’ and will give you lovely crisp shots with little noise/grain, if you bumped your ISO up from 100 to 400 you’ll notice that you can shoot at higher shutter speeds and smaller apertures.


Always ask your self these questions when choosing the ISO setting.

  • Light – Is the subject well lit?
  • Grain – Do I want a grainy shot or one without noise?
  • Tripod – Am I using a tripod?
  • Moving Subject – Is my subject moving or still?

Tip2: If the subject is well lit, need little graininess in the picture plus using a tripod and the subject is not moving; generally a pretty low ISO rating would do the magic.


Tip3: If it’s dark, want grain, not using a tripod and the subject is moving consider about increasing the ISO as it will enable to shoot with a high shutter speed and still expose the shot well. But don’t forget increase in ISO will generate noisier shots.


Don’t forget to push ISO to higher settings, at:

  • Indoor Sports Events – subject is moving fast and have limited light available.
  • Concerts – low in light and those are ‘no-flash’ zones
  • Art Galleries, Churches etc- ‘no-flash’ zones and of course low light.
  • Birthday Parties – in a dark room with candles to blow situation will be ruined by a bright flash. Increasing the ISO can help capture the scene.

ISO is an important factor of digital photography. Experimenting with different settings in your camera and compare the differences it makes on your images will help you to get more practice and knowledge.

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