Understanding Aperture, Shutter Speed, and ISO
Understanding aperture, shutter speed, and ISO should be the first thing every new photographer learns. Being aware of how they work together will not only help in getting proper exposure in a shot, but will also lend to different artist options you might want to make as a photographer. For instance, let’s assume you’re taking a picture of a waterfall. Do you want to see each speck of water as it splashes on the rocks, or would you prefer the water look more like a steady and smooth rush as it passed over the rocks? Or maybe you’re taking a portrait. Do you want everything in the picture in focus, or just the person you’re photographing where the background is a smooth blur?
Both of those choices, and several others are effected by our aperture, shutter speed, and ISO and how they work together. Let’s break down what each of them does, and how they can effect your photo.
Aperture determines the size of the opening in the lens that light passes through. If you’ve ever looked at a lens you’ve probably seen the blades inside that open and close to create a larger or smaller opening. This opening allows more or less light into the camera and is determined by the f-stop you choose. Oddly enough, the f-stop and aperture have an inverse relationship. As the f-stop gets smaller, the aperture (size of the opening) gets larger, and when the f-stop goes up the aperture gets smaller.
The aperture determines how much light passes into the camera body to capture the photo. The aperture also plays a big role in the depth of field of the photo. Depth of field is how much of the photo is in focus, and how much is out of focus. An example can be seen in photos where the person photographed is in detailed focus, and the background of the photo is blurred. That would be a small depth of field achieved by using a large aperture (small f-stop). On the opposite end of the spectrum, a small aperture achieved by using a high f-stop creates a large depth of field resulting in more of the picture being in focus.
Shutter speed is how long the shutter stays open for when you shoot a photo. The longer the shutter is open, the more light that is allowed to pass through to the sensor. Like the aperture, the shutter speed can have a huge effect on the look of photo when it’s taken. It can turn what would be a great looking photo into a horrible one. If you’re having issues where photos are coming out blurry, chances are that it’s due to your shutter speed.
The longer the shutter is open, the more light it allows the sensor to capture which creates the image. This is where the blur comes from, particularly when a subject is moving and the shutter speed is slower. A good example are the photos of highways with the streaking lights from cars. That’s caused by a slower shutter speed where the shutter is open longer and catching the movement of the subject. A faster shutter speed, one where the shutter opens and closes faster, catches more of the exact moment.
ISO is how sensitive your camera’s image sensor is to light. Higher ISO’s make it easier to capture images when there is not enough light by making the sensor more sensitive to the light that you do have. On the other hand, when you’re shooting in an area that has a lot of light, chances are you’ll want to turn the ISO down to make the sensor less sensitive to the light.
This does come with some caveats though. When you shoot a photo that tends to have a lot of grain in the picture, the ISO setting is in most cases the reason why. When shooting in low light, pushing the ISO up helps in getting a better picture as the sensor becomes more sensitive to capturing the light to get the photo. This comes with the problem of also introducing grain to the photo. How high you can push the ISO without introducing grain depends a lot on the camera. Some cameras can go higher with the ISO than others before the grain becomes noticeable.
You’ll notice that all three of these effect lighting and how light works with the camera to get the final picture. Photography can truly be said to be the ability to paint with light, not only in the way it’s used in the photo to light the subject but in how the camera manipulates it to capture the image. While the descriptions above describes how each of these items works independently, they are tied to one another in that changing one usually requires changing another to get proper exposure. In a later article we’ll discuss how they tied to one another and work together to capture the image you’re looking to achieve.