Not Using Auto ISO? You’re Missing Out

Auto ISO is one of those features that I ignored for a long time, considering it nothing more than a gimmick. It was only recently that I decided to give Auto ISO a try, and quickly realized that I was missing a valuable and convenient feature.

Auto ISO explained

As the name suggests, in Auto ISO mode, the camera selects the correct ISO value for the scene being measured. Initially, the idea of ​​letting my camera choose the ISO value not only seemed silly to me, but also like a very bad idea, because I was afraid that I would end up with grainy images if the camera chose a very high ISO. raised. I was also firmly in the mentality of a film shooter, as I grew up in a time when using ISO 800 film pushed the grain boundaries and was generally only used as a last resort. . Obviously, the world changed a long time ago, but as many of us know, old habits die hard, especially for us photographers!

The beauty of using Auto ISO is the ability to customize. The camera doesn’t just select the appropriate ISO for your exposure, but gives you a number of other options to ensure you don’t end up with extremely grainy or blurry photos. In this article and video, I explain how these features work with a Canon EOS camera, but the basics will work with any camera with auto ISO, although customization levels vary by brand. .


Once you’ve set your camera to Auto ISO, you can tell the camera the lowest and highest ISO it’s allowed to use using the “Auto Range” menu. At first I thought of auto range as a high ISO cap, leaving the low ISO at 100 and setting the high cap at around 3200, which I thought was the most grain I would want to see in my images. I quickly realized that wasn’t the best way to use the feature and now fine tune it a bit more to specific shooting conditions and not just acceptable grain levels.

For example, suppose you are shooting portraits of sports, children, or any subject that moves a lot, outdoors on a bright sunny day. In this situation, the minimum ISO level is just as important as the maximum, because in general you don’t want the camera to use 100 ISO for moving subjects, even outdoors on a sunny day. It’s much more practical to have the minimum ISO set to 400 in this situation, as you want the camera to choose as fast a shutter speed as possible if you’re shooting in auto or aperture priority mode, and the difference between 100 and 400 for most applications is negligible. If the camera chooses a slower shutter speed because you let it decide on an auto ISO of 100, for example, the photo may be blurry. As another example, if you know you’ll be in a dark room where 100, 400, or even 800 ISO won’t do, make sure your low ISO auto range reflects that. In general, my suggestion is to keep the low and high ISO range closer rather than far for best results.

This all might sound obvious, but it took me a while to figure it out, probably because I come from a time when we did our best to use the lowest possible ISO at all times, when possible. Today, I don’t think this applies everywhere as strictly as it used to, and I will even shoot at ISO 400 or 800 in my studio if the situation calls for it.

Minimum shutter speed

With a Canon EOS body, you can also choose whether the camera automatically or manually selects the minimum shutter speed it will use when shooting in program or aperture priority. When set to manual, you can tell the camera that the slowest shutter speed you want to use is 1/500s. This is another customizable security measure that helps ensure sharp photos, and the camera won’t use any speeds lower than what you dial.

Much more interesting is the automatic minimum shutter speed setting, however. With this setting, the minimum shutter speed is set automatically, but it is based on the focal length of the lens you are using. By adjusting the menu slider, you can tell the camera to use a faster or slower shutter speed than the focal length of the attached lens. So if you are using a 200mm lens for example, the camera will not use a shutter speed slower than 1/200s in the default mode. By sliding the auto setting to “faster”, you can force the camera to use a faster shutter speed in one-stop increments, up to three stops. By choosing slower, the opposite happens. This, in my opinion, makes Auto ISO a very handy and flexible feature, even for someone like me who shoots mostly manually.

Auto ISO and aperture priority: a great combination

By far the most common way to use auto ISO is when shooting in aperture priority. In this mode, the camera selects the shutter speed and ISO, and I simply dial in the aperture I want. As a portrait photographer, selecting a wide aperture is almost always my primary concern, and with two young children, I find it to be one of my favorite ways to shoot. I like not having to worry about the camera choosing too slow a shutter speed for fast-moving kids or setting an ISO so high that my images look too grainy. By dialing in my automatic ISO settings, I’m able to retain creative control in situations where I don’t have much time to play with the settings, in other words, in any situation where children are involved! I found myself using Aauto ISO with aperture priority more and more when I leave my studio and work in natural light, whether taking pictures of children or at a concert in a dimly lit room.

Exposure compensation

The final benefit of using auto ISO is that you can always adjust exposure compensation and fine-tune your image. I often like to intentionally overexpose or underexpose images to create certain effects, which is why I usually shoot in manual mode. But, as with my other misconceptions about auto ISO, I first thought it would override exposure compensation, and it doesn’t. This adds even more flexibility to Auto ISO, as I still retain a fair amount of creative control. And, I often find myself changing ISOs on the fly during a shoot, especially if the lighting situation changes quickly, so Auto ISO is an extremely handy tool that can save you a lot of time.

Try it!

Auto ISO, like any other feature of a modern camera, has to be experienced. It’s not for everyone, but I think a lot of photographers may dismiss this valuable feature as not being for them. I know I did, and I’m glad I finally tried it, because I added a valuable tool to my photography toolbox.

Leave a Comment