How to get shutter speed slower than 1 sec while using auto iso in Av/P

[Enphyrus]

Hi, community. I've recently switched to canon and found that the cap of 1 sec in "Minimum Shutter Speed for ISO Auto" is annoying. Is there anyway of disabling the limit? I am acknowledge that shutter speed can be pushed beyond 1 sec with "Set shutter speed range", yet it does not quite fit in scenes where exposure changes dramatically, i.e. day to night timelapse.

[Waddizzle]

Don’t allow the camera to control more than one leg of the Exposure Triangle.  Don’t use ISO Auto in P, Av, or Tv modes. 

Also, the above modes can override your settings because of a feature called Safety Shift.  I keep it disabled. 

[p4pictures]

Minimum shutter speed for ISO auto works in the following way. 

AUTO - the camera uses the lens focal length to determine the minimum shutter speed to avoid camera shake when using P or Av mode with ISO set to AUTO. So for a 500mm lens, the camera will increase the ISO value to achieve 1/500 shutter speed if possible. When set to AUTO you can adjust the calculation to be up to 3-stops slower or faster, so with 3-stops slower the shutter speed can be as slow as 1/60 with a 500mm lens before the camera raises the ISO. 

If you choose a manual limit, the slowest option is 1 second and the fastest 1/8000. This means the setting is hard and not dependent on the focal length. So in low light the camera will raise ISO to achieve the minimum shutter speed set. However if that is not possible the ISO reaches the upper limit allowed by the auto ISO range then the camera will go for a slower speed. 

As pointed out by my colleague if you have safety shift enabled then it can switch the camera out of it's fixed ISO value in to auto and then the above information is valid. 

A a quick test I fitted a 40mm lens to my camera and selected f/11 aperture. With the min shutter speed set to auto, the camera selects a shutter speed of at least 1/40 until it needs to increase the ISO as the brightness of the scene reduces. With the lens cap on the lens, the ISO reaches the maximum limit set on the camera for auto ISO, and then the shutter speed goes below 1/40. In my case I see 25 seconds and ISO 25,600 on my camera with the lens cap on.

When I repeat the test with a manually set 1 second shutter speed limit the same result is as for the auto setting above. 

You didn't mention the camera you are using, but some have the ability to limit the shutter speed range. This limit is a hard limit and it is always active regardless of the mode or other settings. So if I set restrict the shutter speed to 1 sec with this, then I cannot select slower than 1 sec in any mode, and the camera can not go slower than 1 sec in any mode where it controls the shutter speed. 

[Danny]

Thanks for joining the conversation, Enphyrus!

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