ISO on digital cameras

Digital cameras record an image using a sensor that converts light to analogue signals, which are then processed in the camera to create a digital image. The sensitivity of the sensor (the ISO) can be increased or lowered to suit the situation you're taking photographs in. For example, If you're at a rock concert where there's going to be hardly any light you'll have to use a higher ISO (perhaps 1600 or even 3200) whereas a landscape shot outside with plenty of light can use a much lower ISO say 100 or 200.

Most DSLRs have ISO speeds which range from ISO200 to ISO3,200. Others go down as low as ISO100 or up as high as ISO6,400 and ISO12,800.

Capturing the image is important, but when you increase the ISO the more likely your pictures will be subject to digitial noise. This is where randomly-spaced, brightly coloured pixels appear in your image.

The above picture was taken on ISO12,800 and there's plenty of digital noise for you to see.

The above picture was taken on ISO100 and as a result, there's less noise.

In most situations it's best to fix the camera on a lower ISO setting so you're assured your image will be of the highest quality, but you may need to use a tripod in lower light conditions to stop camera shake spoiling your photograph.

Move the slide to see how ISO can change an image:

So to clarify, the less light you have the higher ISO you'll need but where possible, to prevent the appearance of noise and other artefacts, keep your ISO as low as possible.

We hope you enjoyed and learned a few things with this article from the ePHOTOzine Academy Series. This is just one part of a 13 part series - to view others follow the links below:

• ePHOTOzine Photography Academy - Part 1: Camera types
• ePHOTOzine Photography Academy - Part 2: Camera lenses
• ePHOTOzine Photography Academy - Part 3: File types
• ePHOTOzine Photography Academy - Part 4: Apertures explained
• ePHOTOzine Photography Academy - Part 5: Shutter Speeds explained
• ePHOTOzine Photography Academy - Part 6: Exposure modes
• ePHOTOzine Photography Academy - Part 7: Metering explained
  
• ePHOTOzine Photography Academy - Part 8: Autofocus explained
• ePHOTOzine Photography Academy - Part 9: Focus Lock
• ePHOTOzine Photography Academy - Part 10: Drive modes
• ePHOTOzine Photography Academy - Part 11: The ISO speed setting
• ePHOTOzine Photography Academy - Part 12: White Balance
• ePHOTOzine Photography Academy - Part 13: Flash modes