Why is my Canon DSLR raising ISO in Av mode instead of using a slower shutter speed?

Asked 12/2/2016

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On a Canon EOS 7D Mark II in Av mode, I want to shoot a stationary subject in low light at f/5.6 and ISO 100, using a tripod if needed. Instead of selecting a longer shutter speed, the camera seems to stay around 1/30s and raises the ISO. Is this expected behavior, or is there a setting I should check?

auto-iso canon av-mode iso exposure

Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0

Photography Stack Exchange contributor

9y ago

2 Answers

I've found this quirk on the 5D IV.

In Av mode, if the ISO is set to A, it still allows you to change the ISO via hardware buttons. But then when you release the shutter, it decides whatever ISO it wants.

Open the quick menu and make sure your ISO is set to a specific setting, not auto.

Originally by user47050. Source · Licensed CC BY-SA 4.0

user47050

9y ago

AI Answer

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This is usually caused by Auto ISO being enabled, even if it looks like you’ve selected a manual ISO value. On some Canon bodies, Av mode with Auto ISO can favor a minimum shutter speed and then raise ISO rather than letting the shutter get longer.

Check the Quick Control screen/menu and confirm ISO is set to a fixed value like 100, not Auto. If ISO is truly fixed, Av mode should normally choose a slower shutter speed in low light.

One community member tested a 7D Mark II in Av at ISO 100 and f/5.6 and it behaved as expected, so this is likely a settings issue rather than normal operation. If all settings are definitely correct and it still happens, then a camera malfunction is possible.

Why is my Canon DSLR raising ISO in Av mode instead of using a slower shutter speed?

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