Photography Basics: Aperture

Have you ever wondered how photographers get those amazing blurred backgrounds, only having the subject in perfect focus? The secret to it is really no secret at all! It's simply knowing how to use your aperture! But before you can use it, you have to know what it is.

An aperture is an opening in your camera that limits the amount of light let into the camera. The aperture of the camera is similar to the pupil of your eye. When your pupil dilates (generally in low light conditions, like walking to the bathroom in the middle of the night) it gets bigger to let in more light, so things that you weren't able to see before in those dark conditions you can see now with clarity. However, when your pupil contracts (in very bright situations, like being outside at noon) it gets much smaller to limit the amount of light needed to see objects clearly. An aperture works the same way. The bigger the hole, the more light is let in. The smaller the hole, the less light.

With me so far?

Aperture is expressed in terms of f stops, for example, f/1.8 or f/16. The larger the number, the smaller the aperture is. The smaller the hole, the bigger the aperture is. It's confusing, but once you get in there and start practicing with it, it becomes a lot easier to understand. Just remember, small number, big hole. Big number, small hole.

So let's put aperture to use. Here are three examples of a photo with three very different apertures.

 f/1.8

 f/5.6

f/13

Yes, this is Chewbacca. My two year old volunteered him for a photo shoot today. ;)

You'll notice in the first picture Chewbacca stands out from the background. He's perfectly in focus while the rest of the blanket and chair behind him are blurred. However, in the last one, you can see everything in almost perfect focus. What you'll also notice is that the quality of the third picture is terrible compared to the first. I had to bump my shutter speed down to right around 1/30 and my ISO all the way up to 6400 in order to make sure the last wasn't underexposed because of the super high aperture (bigger number, smaller hole, less light). 

Another thing to remember about aperture is that it works on a geometric plane. Take a look back at the first picture.You'll notice that directly in front and behind of Chewbacca are blurred, but to the immediate left and right, it's just as equally in focus as the subject. While you're out shooting, make sure you keep on eye on the plane.

When to use a higher versus lower aperture

I know a lot of people who shoot with their aperture wide open (at the lowest f-stop), I can be one of them! There are some situations where having a higher f-stop results in a better photo than a lower one. City skylines, photos of mountains, streams, waterfalls, all are better with a higher aperture because you want every detail of it captured. A lower f-stop is preferred in portraits, pictures of your loved ones, your dog, etc, so that they are the focus of the moment. Another time to use a higher f-stop during a photo session is if you want to capture the surroundings of your subject, the flowers in the background, the beautiful landscape or mountains, etc. What aperture you decide to use is entirely up to what potential you see in that photo! 

Next week we'll finish up the last leg of the exposure triangle: shutter speed! I would love to see your examples of playing with aperture. What aperture range do you prefer the most?