Making the case for Auto ISO

Manual ISO setting

How to set your Auto ISO - step 2

Readers often tell us that one of their most common photography problems is forgetting to adjust the ISO settings on their camera when switching between indoor and outdoor shooting. Many often ask if their camera has a reminder they can set.

Well, kind of. The sound of very slow shutter speeds is often a good reminder that you’ve forgotten to increase your ISO setting when shooting indoors or in low light!

Going outside, though, is more of a challenge. 
If you’re sightseeing, shooting a wedding, or in other situations where you’re switching between indoor and outdoor settings, it’s worth considering your digital camera’s Auto ISO function.

Now, suggesting an auto setting to a serious photographer will often draw a look of scorn, but bear with us. Your Auto ISO function will keep the sensitivity as low as possible without giving shutter speeds that are so slow that camera-shake results.

As lighting gets dimmer, Auto ISO will raise the sensitivity by only the amount that’s really necessary, so you should always get a good trade-off between sufficiently fast shutter speeds and the best available image quality.

That’s because pictures taken at very high ISOs are likely to have increased noise and a drop in fine detail. With many SLRs, you can customise the way Auto ISO operates, choosing the slowest shutter speed you want to use as well as defining the maximum ISO permissible.

There are times to avoid Auto ISO. For example, if you want to use a slow shutter speed to create motion blur, you’ll need to apply a low sensitivity setting manually (find out step-by-step how to set your Auto ISO function).

Auto ISO: when to go manual

Auto ISO works very well in most cases, but when you want a slow shutter speed to blur movement, like in this watery foreground above, you’ll need to set the sensitivity manually (learn from some of the common mistakes at every shutter speed – and the best settings to use).

Manual ISO setting

Here we’ve set the ISO manually to get more motion blur in the water and a stronger reflection.

Similarly, if you want to freeze action, you’re likely to need a faster shutter speed than Auto ISO will deliver, especially in dull lighting conditions.

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