ISO made easy: Understanding your ISO settings

ISO allows you to increase the brightness of your image. Let’s help you find out more about ISO.

A handy ISO cheat sheet chart.

What is ISO?

ISO is sort of like volume control for listening to music. If there’s not much signal — in this case, light — you increase the brightness of your image by amplifying the signal.

Film was rated by ISO, too. However, we can now adjust the camera’s sensitivity whenever we want instead of having to change rolls of film! The higher the ISO number, the more sensitive to light our camera is. An ISO of 100 is not very sensitive. An ISO of 6400 is very sensitive.

When should I change my ISO?

We change ISO based on the scene at hand. Generally speaking, the darker the scene, the more we can consider increasing the ISO. If there is a lot of movement in a dark setting, we may want to make our ISO even higher so we can use a higher shutter speed so moving subjects don’t have as much blur. We can also use a flash to help “freeze” the movement.

What ISO setting should I use?

Generally speaking, you want to use the lowest ISO possible. Why? This will give you the “cleanest” images. This means that there is less “noise” in the images. Some might say that a cleaner image looks less “grainy.”  Let’s look at some examples!

Low ISO settings: It’s bright!

It’s bright out! No need for a super-sensitive ISO setting! A low ISO of around 100 or 200 is perfect here.

For bright scenes such as day landscape photos, day portraits, or sports during the day, you would typically use a low ISO settings. This might be ISO 100, 200 or 400, depending on the light and shadow and time of day.

Medium ISO settings

I would choose to use a medium ISO setting of about ISO 800 or so here, although I did manage to use ISO 640 because I had a flash go off.

For scenes that have less light, such as later in the day, in the shade, or in bright indoors settings, we might raise the ISO to a medium ISO setting, such as around ISO 800 or 1000. As with all settings, adjust this until you get a strong exposure with a lot of information.

High ISO settings — not too much light right now!

ISO 4000 during a 20-second exposure at night because starlight is not very bright.

You might use these for very low light settings, such as nighttime, dark indoors, concerts, plays, lower-light sports, and other events. This could be from ISO 1600 and up. 

Remember, the higher the ISO, the more noise you might have in your images. However, I’d rather have a noisy image than a blurry image (unless I want blur, of course). Many modern cameras and even phones can take surprisingly clean photos in low light. There’s also software that can help you lower the amount of noise while still retaining detail.

Concert photography. I would never use a flash this close to a performer here. Since he was moving around, I used ISO 1600, a relatively high ISO setting, to “freeze” him in place and prevent blur.

Should I use Auto ISO?

The short answer is “it depends.” Auto ISO allows the camera to choose the best ISO for a particular situation. It makes this decision for you depending on what lens you are using, how much available light there is, and what your shutter speed is. Conveniently, it does this from picture to picture!

There are some scenarios in which you could consider using Auto ISO. I would consider using it if your light is unpredictable and keeps changing, you are constantly wandering in and out, or you are photographing rapidly and don’t want to keep adjusting. A camera’s Auto ISO options are sophisticated and can do a great job of making these decisions for you. 

“Real photographers don’t use Auto ISO”

You may occasionally hear someone saying that a “real” photographer will not use Auto ISO on your camera. They say that you should be able to adjust everything manually on your camera. While I am a huge proponent of having photographers understand the exposure triangle (shutter speed, aperture, and ISO and their relationship to each other), I also am a realist. If I encounter the scenarios described above, I just might go ahead and use Auto ISO. If I get great results and it’s easier, then I’m happy.

Of course, there are times in which you might not want to use Auto ISO. Sometimes you might want to set your ISO manually for creative purposes. Or sometimes, you might know better than the camera and want to make the decisions. That’s OK too. This is why it’s good to have an understanding of ISO.

You don’t always have to increase ISO when it’s dark

Event photography
I used ISO 400, which has low-sensitivity here, even though it was indoors. Why? I was using a flash, which illuminated the subject. On this particular photo, I kept the room dark with the low sensitivity because I wanted them to pop out. Note that this is not typically how one does indoor event photography, but I wanted to do that because the windows in the back were very bright and distracting otherwise.

If you have a tripod and nothing is moving (or you don’t care if it is moving), you can still use a low ISO. You can use a longer shutter speed to make up the difference. If you are using a flash to illuminate the subject, you might not need to increase your ISO as much either. 

More tweaky stuff

Every time you double your ISO, you increase the camera’s light sensitivity by a full exposure “stop.” Typically, the full-stop ISO scale progresses like this: 100, 200, 400, 800, 1600, 3200, 6400, 12,800 and so on. See how the numbers keep doubling? The light sensitivity doubles. And so does your brightness. For example, ISO 200 is twice as bright as ISO 100. ISO 400 is twice as bright as ISO 200.


Head on over to the Ken Lee Photography website to purchase books or look at night photography and long exposure prints and more.  My books are available there and Amazon, Barnes and Noble, Target, Booktopia, Books A Million, IBS, and Aladin. If you enjoy the book, please leave a nice review, thanks!


Night photographers Tim Little, Mike Cooper and I all use Pentax gear. We discuss this, gear, adventures, light painting, lenses, night photography, creativity, and more in this ongoing YouTube podcast. Subscribe and watch to the Nightaxians today!

Ken Lee Photography Facebook Page (poke your head in, say hi, and “like” the page if you would, uh, like)

Behind the Shot video podcast – interview February 2020


How We Got the Shots: Five Photographers, Five Stories – Night Photo Summit 2022


Ken Lee’s Abandoned Trains Planes and Automobiles with Tim Little of Cape Nights Photography
Conversation about night photography and my book with Lance Keimig of National Park At Night

A Photographer Captures Haunting Nighttime Images of Abandoned Buildings, Planes, and Cars in the American Southwest – Business Insider by Erin McDowell
A Photographer Explores Southern California’s Desert Ruins – Los Angeles Magazine article by Chris Nichols



One thought on “ISO made easy: Understanding your ISO settings

  1. I tend to think of ISO as “fake light” – with the possibility of “noise” added at no additional charge. The secret is, be aware of the situation / environment you’re shooting in – as much as possible and be familiar with your particular camera.

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