The Basics of Photography - ISO
Photo by Braydon Cottrell (Author)
Ah finally, the final piece of the exposure triangle. ISO. Let’s take a look at what ISO is and how it affects our images!
What is ISO?
ISO is the third side of our lovely exposure triangle. In simple terms, this dictates how sensitive our camera is to light and is measured by a whole number. For most beginners ISO is the easiest concept to grasp. The lower the ISO number, the less sensitive the camera will be to light and the higher the ISO, the more sensitive the camera will be to light. If you’ve read the other articles about shutter speed and aperture, you’ll know that there is always a downside. With ISO as the value gets higher, you will be increasing the chances of introducing grain, also known as “noise”, to your photos. A lot of beginners don’t realize they’ve introduced grain into their images until they get home and pull the image up on a larger screen. Grain is generally much harder to see on a smaller camera screen and is much more noticeable on a computer monitor. Personally, I see this with a lot of beginner photographers who are shooting indoor sports or events. A lot of the time they are using a kit lens that has a maximum aperture of around f/4 and even with it opened all the way up, their image is still too dark, so they crank the ISO up to brighten that image, and by doing so they make their picture super grainy without realizing it. Now, there are ways to reduce grain in post processing, but it isn’t always perfect. It’s also good to get in the habit of getting as many things right during your shoot and reducing the amount of “I'll just edit that out in post”.
Let’s put it all together
Finally, you now should know about the three sides of the exposure triangle. Aperture, ISO, and Shutter Speed. So lets put them all together and see how they work with a few examples!
Photo taken by Braydon Cottrell (Fujifilm XT5 - 41mm - 12800 ISO - f/10 - 1/7000s) - Clinton County Fairgrounds, IN
Alright so let’s look at what I would call an extreme example. Right from the get go you likely notice how much grain this photo above has. Why is it so grainy? Well it’s like this due to the high ISO of 12800. Now this was a creative choice on my part. I personally love grainy black and white photos as it gives them an older feel and that’s just part of my style. But I love this photo as an example because it shows us how each side of the exposure triangle works with one another. So let’s start with ISO. This image was taken during a bright sunny morning, which means lot of harsh and bright light. With an ISO of 12800, that means my camera is incredibly sensitive to the already bright sunlight. To combat this and make sure the picture is properly exposed, I needed to now look at my shutter speed and aperture. As we previously learned, aperture is the hole in our lens that lets in light. Since this photo was already very bright due to the high ISO, I needed to make it darker. So I narrowed my aperture, or made the hole smaller by increasing the f/ stop number. For this photo, I used f/10 which means the hole in my lens is going to be pretty small, letting in a much smaller amount of light and forcing more things to be in focus. Now I could’ve gone all the way up to f/16 on my lens and made the aperture super tiny, but we're still forgetting about the other side of the exposure triangle. Shutter speed. This photo is of a horse racing around a track and I wanted to freeze that action in place, but I also didn’t want my picture to be too dark. So I set my shutter speed to 1/7000s, which ensured I was able to freeze the horse in place. And by leaving my aperture at f/10 rather than f/16, there was still plenty of light being let in so that I could have the high shutter speed without the image being dark. Now I probably gone for opening the aperture a little more to brighten up the image a tad, but I’m still happy with how this photo came out.