What is ISO: camera sensitivity settings (and the best ways to use them)

What is ISO: understanding your camera's sensitivity settings (and the best ways to use them)

When to change the ISO

There are so many ways to change the exposure on your DSLR that it’s easy to get lost on a sea of possibilities. It becomes simpler when you think of the ISO setting simply as a means of getting the shutter speed you need. Here are some examples of what we mean.

When to change the ISO: at night

At night on a tripod: ISO100
Always use a tripod for night shots when you can, because when you’ve got the camera locked in position you can use any shutter speed you like – and this means you don’t have to increase the ISO and risk noise, even if your exposures run into many seconds.


When to change the ISO: snapshots after dark

Snapshots after dark: ISO1600
The latest DSLRs can get great shots even at really high ISOs, so it is perfectly possible to shoot handheld indoors and after dark. But you will need a fast enough shutter speed to avoid camera shake, so try ISO1600 to start with, or use the Auto ISO function.


When to change the ISO: low-light sport

Low light sport: ISO6400
The problem here is subject movement. Sports are fast moving and you’ll need a fast shutter speed of 1/250 sec or 1/500 sec to have any chance of freezing the action. This means you may need a very high ISO indeed – but that’s better than blurred pics.

SEE MORE: ISO settings in low light – when and how to increase your camera’s sensitivity

Using Auto ISO

The main reason for increasing the ISO in dark conditions is to make sure you can shoot at a suitable shutter speed. At the same time, you’ll want to shoot at the lowest ISO you can, in order to get the best possible picture quality.

This means you can end up doing complicated mental maths right at the time when you should be concentrating on your pictures. But there’s no need, because your DSLR can do it for you!

The Auto ISO sensitivity option lets you set the minimum shutter speed you want the camera to use and the maximum ISO, then works out the best combination instantly as you shoot.

PAGE 1: What is ISO?
PAGE 2: See the difference in high vs low ISO settings
PAGE 3: Easy ways to keep the noise down at higher ISO settings
PAGE 4: When to change the ISO


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  • Jørgen Guldmann

    The ISO setting do not change the sensitivity of the camera. Digital cameras only have one sensitivity (base ISO) determined by the efficiency of the sensor. ISO is an indication of the post-sensor amplification of the signal.

    There is more on base ISO on my blog entry

  • Very clear and easy to understand

  • Mike McNamara

    Another great article. I always bookmark these for future reference.

    However I have a question; are they available as PDF’s? The reason I ask is that as well as bookmarking them I print them to PDF, but due to the enormous number of links on each web page, the PDF tends to be very ‘long’. 19 pages in the case of this item for two pages of reading content. The same is true for the follow on pages 2,3,4 of this article.

    Is there a way that your website could capture the relevant pages for printing to a PDF or that you could make them available in PDF for saving via link on the page?