Video: Understanding Auto ISO
Auto ISO, and specifically the ability to cap it at a limit you choose, is one of the more useful features in the newest generation of DSLRs and mirrorless cameras, especially so when you're shooting genres with constantly changing light and subject matter, like sports, wildlife, street and event photography.
In this video, Steve Perry takes a look at what auto ISO does, why and when you should use it, how to set it up, and how it interacts with your various exposure modes.
Although Perry speaks specifically about Nikon cameras in this video, there's enough here for you to apply the same information to other brands too, as auto ISO functionality is relatively consistent regardless of what you shoot with.
If you do happen to be a Nikon shooter you're in luck however, as Perry shares a cheat sheet with his preferred maximum ISOs for a variety of different Nikon cameras. Otherwise, if you do use auto ISO, do some test shots to find out at what ISO the level of image degradation you are comfortable with is, and then choose this as your highest possible setting.
You can see more of Steve Perry's videos on YouTube.