We’ve talked about shutter speed...and aperture. And yes, they can be a bit confusing. Not just what each of them do, but how they affect your photos. And each other. I get it.

So why would I throw yet another something into the mix? Maybe I’m just mean like that. Or maybe it’s one of those things that I’m doing for your own good. Because you need it. Like broccoli.

What is ISO exactly? How does it affect your photos? Let’s talk about that.

ISO is a camera setting that will brighten or darken your photos. Which means it can help you capture images in darker environments. It can also help you have more flexibility with your aperture and shutter speed settings. Confused? I thought you might be. Let’s take it one step at a time…

Remember back in the day when we used film in our cameras? Well we purchased the film based on the ISO number, which was a measure of the film’s sensitivity to light.

So if we planned to make photos outside on a sunny day we might buy 100 or 200 ISO film. Not so sunny out or making photos inside? Maybe we’d grab the 400 film. When digital cameras came about, they kept the ISO measure as an indicator of light sensitivity of the camera sensor. Now this indicator of “sensor sensitivity” definition for digital cameras is debatable, as evidenced by multiple conflicting articles online. So if it helps you understand the concept, then excellent. If you want to do your own research and come up with your own definition? Then be my guest.

An image inside a museum that I would not have been able to get without ISO pushed up to 6400. Specifically this is the Musée Toulouse-Lautrec in Albi, France. I highly recommend it!

Moving on. When deciding which ISO setting to use, here are some general guidelines. Start with 100-200 if you’re making photos outside on a sunny day. If it starts to get cloudy, or the sun goes down? Bump up that ISO to say 400 or so. The higher the ISO, the darker the environment you can make photos in.

If you head inside, but it’s bright and sunny? Try ISO of 800. Now if you’re inside and there’s low light, you’re looking at 4600+ for your ISO settings. And the darker it gets? The higher the ISO number needs to go. I often shoot at 6400 inside because the lighting is often iffy.

So you can just crank up your ISO as high as you need to? Well...yes. But there’s a tradeoff. Nothing in life comes free.

What is that tradeoff? Noise. Or some say grain. It looks like tiny colored pixels or specs in your photos, similar to the grain you’d see in old photos. It sounds worse than it is. Some photographers actually like grain, and add it INTO photos for artistic effect. And then some (who are more the technical perfectionists of the crowd) do anything to avoid it. I don’t hate it, myself. And the other thing is that it’s pretty easy to improve upon in post-processing.

All right so ISO can give you the flexibility to make photos in darker conditions. Check. The darker the conditions, the higher the ISO number you want. Check. BUT the higher the ISO number the more noise you’ll get in your photos. Check.

All of that make sense so far? Okay, let’s dive in a smidge deeper then.

I mentioned that ISO can also help give you more flexibility in choosing your shutter speed and aperture settings. Stick with me here, this is where it can get a bit confusing.

Let’s say you’re going to make a photo of your sweet little dog. A shallow depth of field, portrait style photo. You’re inside your house and the light is pretty low. You’re shooting in aperture priority mode, and you choose your aperture of f/4. But the shutter speed that goes along with that aperture is only 1/30 of a second. Eek that’s pretty slow.

What happens when you shoot with a slow shutter speed? Well if it’s too slow (and 1/30 probably is) then you can’t handhold your camera steady enough to make a focused shot. What happens with a slow shutter speed, is that you’re not quite steady enough and the camera moves slightly while making the photo. And then? Your photo is blurred. Crap! The perfect expression, the perfect lighting of sweet little Princess, but the photo is blurry.

This is a painful example of the blurry photos I used to get before understanding my camera settings, and specifically ISO superpower. This was shot at f/5.6, shutter speed 1/8 second, and ISO 200…even though it was evening and the light was low. Ug… — This is a painful example of the blurry photos I used to get before understanding my camera settings, and specifically ISO superpower. This was shot at f/5.6, shutter speed 1/8 second, and ISO 200…even though it was evening and the light was low. Ugh.

And this, my friend, is where ISO comes in. Like a superhero “here I come to save the day!!” Are you picturing ISO flying in wearing a cape? You should be. Because that’s just how awesome it is, once you understand how to work together as a team. Yeah kind of like Batman and Robin.

Back to Princess and her portrait. You have your camera on aperture priority mode, and choose the aperture of f/4. And then you observe that crazy low shutter speed of 1/30 second. What do you do? You bump up your ISO to say 400, and check your shutter speed again. Still not fast enough? (I would say aim for AT LEAST 1/60 or 1/80 of a second IF Princess is sleeping. If she’s moving then you might want more like 1/250 second).

Keep adjusting your ISO up until you get the shutter speed that allows you to handhold your camera (for a still object at least 1/60 second, and for moving objects at least 1/250 second).

Now see what I mean about ISO saving the day?? You can adjust your camera settings, and make photos without bright light. And without a tripod (unless you want to avoid all noise, then you’ll need that tripod afterall). AND with the camera technology ever improving, it’s even possible to make photos at night when you’re traveling WITHOUT a tripod!

Now that does mean a LOT of noise when you’re shooting at say 10,000 ISO. But who wants to lug a tripod around with them on vacation? I’m happy to accept the noise in exchange for being able to make photos whenever I want, in whatever light I want. Even inside museums, or cathedrals (if allowed of course).

This is an example of how I was able to adjust to a hand-holdable shutter speed (I think I’ve just coined a new phrase) of 1/60 second even when the light was getting low, by increasing my ISO to 400. My aperture is f/13.

I’m telling you, ISO is going to be your new best friend. You’re going to go from those inside dim shots that are now kind of (or a lot) blurry, to inside dim with focused attention to details and some noise that you can mostly remove (if you even want to).

I’ve been outside, snapping away, when the sun starts to go down and ALL of my photos were out of focus. Did I say ALL of them?? I wanted to cry. That was before I understood the concept of slow shutter speed = blurry photos. AND before I discovered the ISO superhero hiding in my camera.

This is another example of how ISO allowed me to even remotely consider making a photo. It’s nighttime in Barcelona, Spain and I had no tripod. But with an ISO of 4000, an aperture of f/4, I was able to get a hand-holdable shutter speed of 1/80 seco… — This is another example of how ISO allowed me to even remotely consider making a photo. It’s nighttime in Barcelona, Spain and I had no tripod. But with an ISO of 4000, an aperture of f/4, I was able to get a hand-holdable shutter speed of 1/80 second.

The best way to make sense of all of this?? You guessed it. Get out your camera. Try it in aperture priority mode, and change your ISO from 100 to 200 to 400 all the way to 6000 and as high as your camera will go. And just see what the difference is. Observe how the shutter speed changes, how the brightness of your photos changes. AND observe the noise or grain in your photos.

Trust me on this. Once it makes sense you’ll have a whole new realm of possibilities, you and your camera.

To help make a little more sense of Aperture, Shutter Speed, and ISO, I created the handy Camera Setting Cheat Sheet. Grab that here.

Have fun trying out your new knowledge of ISO and let me know how it goes!