How to Preview Depth-of-Field with a Canon DSLR Camera

I’d like to continue on with the theme of “depth of field” for just a little while longer. If you haven’t seen my previous post on the topic, you can click through to read up on things here:

The Basics of Depth of Field For Photography

I didn’t go nuts in that post and try to explain the universe, but I did cover enough to get familiarized with what depth of field is when it comes to photography. In today’s post, I’d like to take things a step farther and talk about depth of field in the real world. Or, at least how we can preview it with our DSLR cameras. Most modern cameras have the capability to preview what exactly will and won’t be blurred or sharp in an image and I’ll discuss how we can see all that in real time below. For this post though, I’ll be using a Canon Rebel T6i. But really, many cameras are very similar when it comes to this function.

F/5, 1/100 second, ISO 4000, 18-135mm @ 67mm

What’s the Problem?

I can remember a long time ago when I first began playing around with my new DSLR camera. I read all about the various settings and was super excited to try them out. One particular setting, Aperture Priority mode, was especially interesting to me because I thought it would give me the ultimate creative control when it came to blurring and keeping things sharp in my photographs. While I was eventually able to harness that power, I wasn’t able to immediately. I’ll explain what I mean below.

This was the situation; I would take my camera outside, change the mode to Aperture Priority and then start shooting subjects, such as flowers and other stationary objects. I would change the aperture size every now and then to see what types of shots I could get. It didn’t take me long to realize that as I was taking these photographs, the resulting images didn’t look anything like what I saw though the viewfinder or the live view screen on the back of the camera. I was purposefully going for a specific type of blurry look in the foreground and background sometimes and a much more sharp one other times. What I noticed was that the camera showed me the same exact preview through its two preview methods with every single photo I took. I thought something was broken.

The Reason Cameras Do This

When previewing a photograph, you need to be able to see things bright and crisp and as easily viewable as possible. If you’ve got the aperture set to its smallest size, not much light is going to come through the lens. That’s going to darken the scene down quite a bit as you’re looking through your camera or at the rear screen. When you have the aperture set to something quite small, such as F/22, the camera’s shutter speed is going to need to compensate for that lack of light by staying open much longer than it normally would as it’s taking the photo. Because you can’t preview shutter speed, you’re left with just the aperture size preview, which might be too dark to do you any good. I hope I’m being clear here. If I’m not, simply ask me to clarify.

Anyway, because camera manufacturers think it’s more important to have a nice bright preview before a photographer takes a photograph, they’ve chosen to show that preview while the aperture is wide open. That way, as much light as possible will come through the lens and everything will be great. Well, except for those occasions that you actually want to see what an Aperture Priority shot will look like after it’s taken. In those cases, you’ll need to take an extra step.

Previewing Depth of Field

If you’d like to preview the depth of field of your photograph before actually taking the photo, you can. It’s not a problem at all. Do me a favor and take a look at this next photo I share below.

In this photo, there are a few buttons. The large one located in the center top area is the one that you would push if you wanted to remove the lens. Do you see the smaller button right beneath it? This one is called the Depth of Field Preview button. If you were to press this button after setting up a shot and then look through one of the preview methods on your camera, you’d see the scene’s depth of field change to what it would actually look like after the shot was taken. This button allows the scene to be displayed through the actual aperture setting in the lens. Now, as a word of warning, it may not appear as you intent and I’ll explain that next.

What Will You See?

If you already have the aperture setting set to its largest size and then press the Depth of Field preview button, you’re in good shape. You won’t see much of a change at all. It’s only when you begin increasing the aperture number (shrinking the actual aperture size) that things get a bit difficult to see. As I mentioned above, we can’t preview shutter speed and that’s what’s required to compensate for a small aperture. So as you shrink your lens’s aperture down, your preview will get darker and darker. The scene will become more sharp, but it probably won’t do you much good if you can’t see it. If you’re in a very bright area, you may have a chance, but if you’re in a low light setting, this feature might not do you any good. You may need to use another method which is called trial and error. This is just a “take a shot and review it” approach. I’m sure you’re used to this one already. Overall though, this is a handy feature to have and I think you’ll find it useful if you ever need it. Just keep it in mind.

I hope I clearly explained how to use the depth of field preview button on your DSLR camera and I hope I gave you some good background information as well. If you have any questions, please let me know in the comment section down below. You may also ask any related questions in the photo discussion board any time you’d like. Thanks for reading!