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Auto ISO and Its Limits

06/18/2025

If you've taken our Photography 1 course -- or even if you haven't but you've been reading our blog for any length of time -- you already know that there are three camera settings that you need to pay attention to in order to take a properly exposed photo: shutter speed, aperture, and ISO. And you probably also know that I am an advocate for getting your camera out of auto mode and into manual. It's the ability to handle the camera in manual mode that really begins the journey of becoming a skillful photographer. That's not to say you can't take some awesome photos in auto mode, but in auto, you're giving the camera the control, and sometimes you may find you just can't get the photo you want. 
Using manual mode puts you in charge of the camera, and not the other way around. In manual mode, you have full control of those three crucial settings of shutter speed, aperture and ISO. When you get good with them, you will have a much easier time adapting to the conditions you're shooting in, which gives you a much better chance at capturing exactly the image you are envisioning. Manual all the way!

Except ... if you recall our Try This post, you may remember that the settings I recommend as a great starting place are shutter at 1/500, aperture at f/8, and auto ISO. Yes, you read that right. And here's why: when you choose auto ISO, you have only shutter speed and aperture to worry about. Those two settings are dictated, in large part, by whether your subject is in motion or not and by how fuzzy a background and foreground you want to have. That is sometimes enough to think about, so using auto ISO, especially when you use Auto-Exposure Compensation, simplifies the process of setting your camera correctly. You don't have to bear changing light conditions in mind at the same time you're managing everything else, because auto ISO will do that for you. You can focus on the scene in front of you without getting as tangled up in the technology.

Now, while those settings are a decent one-size-fits-most starting point, you may find that the results aren't as pretty as you might hope. Remember that the smaller the number of your aperture setting, the larger the aperture opening, and a larger aperture opening produces a shallower depth of field. A shallow depth of field means a pleasantly fuzzy background and foreground and is often what we strive for with portrait photography, and even some object photography, like a flower in bloom or a bird on a branch. I encourage you to give that a try, and you may find you like it better than the f/8 setting.

As usual, though, there is a caveat, and it has to do with the range of your ISO setting. Depending on your camera, your ISO may top out in the high hundreds or even in the thousands. However, the bottom of the ISO range is 100. If your ISO is at 100 and your shot is still overexposed, you cannot compensate for the overexposure with ISO. You may run into this situation on a very bright day if you have your camera set to 1/500 and f/2.8. But don't despair. If you find yourself faced with this conundrum, the solution is to increase your shutter speed by one setting -- or even higher, depending on what your camera's built-in light meter is telling you -- to compensate for the abundance of light. 

If you find that the operation of your camera controls is getting in the way of getting the images you hope for, our Photography 1 course is a great place to start getting comfortable with them. Or, if you've already been through Photography 1 and just need to brush up your camera-handling skills a bit, you might consider joining us for a Digital Camera Class workshop.

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