Understand Aperture in Photography

Episode Transcript:

G’day, and welcome to Professional Photography Tips. Today we’re going to learn to be apturelutely awesome. Wait, what does that say? A-per-tu, Oh, aperture. Today we’re going to learn about aperture. [Puzzled look, snap].

[snap] There, that’s better.

[opening credits]

Hi everyone, Josh Cripps here. In our last video we learned all about shutter speed and how you can use to control not only motion, but emotion, in your photos. [Click for this video]. Now, shutter speed is only part of the pie when it comes to understanding exposure. The other main ingredient in the exposure recipe is aperture.

The aperture, as you probably know, is an opening in our lens that allows light to enter the camera, and you can set it to be wide open, or tightly closed. And in either case you can achieve a good exposure, so why choose one over the other? To find out, let’s do a little experiment.

Put your camera in aperture priority mode, usually marked with an A or an Av. Now you need a subject and a background. I chose this tree, with those trees behind it, but you can use anything you like as long as there’s some space between you, your subject, and your background. Set your camera up on a tripod zoom in so that your subject fills a good amount of your frame and you can still see the background.

Turn the aperture control dial until the camera reads something like f/4 or as low as you can go [LCD overlay], focus on your subject, then go ahead and take a picture. Now without moving your camera turn the dial the other way till it reads f/22 or higher, and take a second picture.

If we now zoom in on those pics and compare the two and we’ll see that the shot at f/4 has a sharp subject with a blurry background, and the shot at f/22 has a sharp subject *and* a sharp background. [comparison overlay]

This is because of something called depth of field. Whenever you focus your camera on a subject, a little bit in front of it and a little bit behind it is also in focus. The size of that in-focus range is your DOF, so the more that’s in focus from front to back the deeper your DOF is.

Looking back at our test shots, we can see that the shot at f/4 has a shallow DOF, and the shot at f/22 has a deeper DOF. In other words, the bigger you f-number, the deeper your depth of field, and the more that’s in focus. [text overlay]

Why is this important? Well, it turns out that whatever is in focus in your frame will attract your viewers’ attention and whatever is out of focus will repel your viewers’ attention.

And if you think about what this means it’s pretty astounding, because what you have is a way to control exactly what your viewers look at in your photo. So if you’re shooting wildlife or portraits or flowers or anything that has a very clear, dominant subject, you’re probably going to want to choose a small f-number like f/2.8 or f/4 to create shallow dof that draws attention only to your subject. Whereas in a grand landscape photo where you want to lead your viewers on a visual journey through the entire photo from front to back you’ll want a higher f-number like 11, 16, or 22 in order to bring everything in your shot into focus.

[examples overlaid]

Now, you should note that your dof shrinks the more you zoom in, so f/22 on a telephoto lens is not the same as f/22 on a wide angle. So don’t expect to be able to get sharp focus on something right next to you and a mile away while shooting with a telephoto lens, because that means you’re defying physics!

Guys, we’ve been having a lot of fun, but can we get serious for a minute? Because there’s one aspect of aperture that, tragically, wreaks havoc on thousands of unsuspecting photographers every day. It’s the fact that the smaller your f-number is, the bigger your actual aperture is. In other words, f/2.8 represents a massive aperture, whereas f/22 is only a tiny little pinpoint. [graphic overlay]

You can think of it like crowd control: say you’ve got a horde of screaming tweens trying to get backstage at a Justin Bieber concert. If you’ve only got 2.8 security guards on duty, well then there’s a lot of space between them for those teenyboppers to make it through. But if you have 22 guards holding rank, then there’s a lot less space for the Beliebers to make it past.

And it’s exactly like that when it comes to aperture and light. Say you choose an aperture of f/2.8 for a close-up shot of a flower. f/2.8 means your aperture is a large space, which lets a lot of light enter your camera, so your shutter speed will have to be short in order to prevent overexposure.

Conversely, shoot a landscape as f/22 and you’ve chosen an itty bitty aperture. The light is just able to trickle in to your camera, so you’ll have to increase your shutter speed to compensate.

Why does a small f-number mean a big aperture and vice versa? Well, some people say it’s because f-number doesn’t actually represent a physical measurement, but rather a ratio between the size of the the focal length of your lens to light-emitting diaphragm of your lens, and other people say it’s because of magic camera pixies who want to befuddle you.

It’s hard to say who’s right, but what’s really most important is remembering that a big f-number creates a deep DOF but is actually a tiny aperture, and a small f-number makes a shallow DOF but is actually a big aperture. I know it’s confusing at first but keep practicing and it’ll become second nature. You can also leave your questions in the comments of this video and I’ll answer them. [text overlay]

As always, thanks for watching! In our next video I’ll be showing you a practical step-by-step guide to making sure you have everything in focus in your landscape photos so be sure to subscribe.

And don’t forget to visit my website joshuacripps.com for landscape photography, tutorials, workshops and more. Until next time, have fun and happy shooting!

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