It seems like I’ve been hearing about depth of field forever. Even before I was into photography, I heard about depth of field. Depth of field this and depth of field that. It was and is all over the place. And do you want to know the truth about it? I don’t think I ever actually knew a definition for this phrase. I mean, I knew what it was, but I don’t think I could have ever explained it to anyone in any coherent way.
Let me change all that today. I’m going to do my best to alter the trajectory of your life so you don’t fall into the same trap that I fell into. You know, practicing your photography and having all sorts of fun out there with your camera, all the while having no idea what “depth of field” means.
In today’s post, I’ll try to explain the basics of depth of field, when it comes to photography. I’ll give you my very own definition, I’ll talk about what effects the “depth” of the “field” and how you can use the tools at your disposal to add your own creative flair to your photos by way of blurring things out or keeping things sharp. Once you’re finished with this post, you should have the knowledge to rub elbows with the best of them at dinner parties, all the while, explaining the basics of depth of field. You’ll get the “wows,” trust me.
What Is Depth of Field?
Through the ages, there have been many technical definitions for this concept and through the ages, men and women have heard or read those definitions and have forgotten them about 30 seconds later. That’s the shame of technical things. They’re boring and people shy away from them. With this in mind, I’m going to break the concept down for you so can remember these ideas forever.
Photographers talk about a “range that’s in focus when we shoot a picture” when they discuss this topic. That’s fine, but let’s go one step further by tearing the phrase “depth of field” apart. We’ll do this my way.
Okay, let’s pretend you’re looking through the viewfinder on your camera. It can be any camera, it doesn’t matter. They all operate similarly when it comes to this. What you see when you look through that viewfinder we’ll consider the field. The field in depth of field is the scene you see when you’re looking through your camera. Easy enough.
Now, the way cameras work is a bit tricky. Certain things happen in the lens that can alter what is actually in focus when you look through that viewfinder. I’m sure you’ve seen those photos out there that display the foreground as blurry, the center very clear and in focus and the area to the rear blurry again. This is a prime example of how camera lenses affect the depth of field of a scene. To keep things simple, we’ll consider the in-focus area the depth part of the phrase. How “deep” is the in-focus area of your photo? What’s the sharp area’s “depth”? Let me give you an example photo to show you exactly what I’m talking about. I took this photo last night as I was trying to think of something clear to show you today. Something that would help me explain my points. Puzzle pieces are perfect for this type of thing.
F/4.5, 1/50 second, ISO 6400, 18-135mm @ 42mm
If you’ll notice the above photo, the blur, sharp and then blur again follows what I was saying above. Because of a few different factors, the camera lens can only really focus on one very shallow area of the scene. In this case, we’d consider this a shallow depth of field. The in-focus area is shallow, while the rest of the scene is left out of focus. So again, depth of field identifies the area of the scene that’s in focus. To have a shallow depth of field means that a relatively thin or narrow band that travels across the scene is in focus and to have a deep depth of field means that the in-focus band that travels across the scene is much fatter or wider. You can choose the terminology you’d like to use for this.
The example photo up above wasn’t the only example I took. I took many, but definitely won’t need them all here. I do want to give you another example though, this time, of a photo that has a deep depth of field. Notice the difference between this shot below and then one above.
F/29, .80 second, ISO 6400, 18-135mm @ 42mm
In this latest photo, almost everything is in focus. That’s interesting because I didn’t move the camera at all or zoom in or out. All I did was make one small change. Would you like to know what that change was? Read on.
But first, take a look at this nifty comparison shot I just put together.
Factors that Affect Depth of Field
I have these magnifying filters that I screw onto the end of my lens when I want to take really close up photos of things. When I first began using them, I noticed that the depth of field was extremely shallow. When I say shallow, I mean, one nostril hair on a cricket was in focus and all the other ones were out of focus. I wondered why that was and then I remembered that a few different conditions cause changes in the depth of field of a scene. I’ll explain those conditions here.
Focal Length: Have you ever seen those long telephoto lenses out there? Or perhaps you have a lens that you can zoom in really far. Focal length is the capability of a lens to magnify an object that’s far away. In general, lenses that have greater focal lengths also offer shallower depths of field. This happens for a variety of reasons, which I won’t discuss here. I’m trying to stay “focused” on the topic and hand.
Conversely, lenses with shorter focal lengths, such as wide angle lenses, offer deeper depths of field. Again, this happens for a variety of reasons.
Distance of the Camera From the Subject: If you go ahead and begin experimenting with your camera, you’ll find that where you position it in relation to your subject will alter the depth of field you see through your lens and in your photos. You may not change one setting on the camera all day long, but when you go ahead and review your photos at the end of the day, you’ll find that you’ll have a wide variety when it comes to blur and sharpness. In general, the closer your camera is to a subject, the narrower the depth of field will be. Conversely, the farther away from the subject you are, the wider the depth of field will be, all other things being equal.
When I spoke about my magnifying filters above, this is the factor I was referring to. Because the magnifying filters allow me to bring my camera much closer to the subject than I would normally be able to, I experienced a narrower depth of field than I would normally experience. This was all because of the distance of the camera from the subject.
Aperture Size: This is the big one. This is the one everyone knows. When you switch your camera over to use its Aperture Priority mode, you’re essentially telling the camera what you’d like your scene’s depth of field to be, within reason. If you’re going for a creative shot where you’d like some blur in front and behind the subject with the subject itself being sharp, you’ll want a larger aperture. Larger apertures use lower numbers. You can read all about aperture here. By the way, for the first demo photo I showed up above (the one with the blur), you can see that I used a large aperture. That setting was F/4.5.
Now, if you would like to have as much clarity in your shot as possible, you’d want to shrink down the size of the aperture. Shrinking the aperture means increasing the number. In the second photo I displayed (the sharper one), I used an aperture of 29. That’s pretty small, but you see the results.
When to Use Certain Depths of Field
Of course, you can do anything you’d like with your camera and your photography, but there are some pretty simple rules to follow when it comes to setting your own depth of field. When you’re going for a creative look with blur, use a more shallow depth of field. When you’re taking a photo of something that you would like isolated in your shot, such as a person sitting for a portrait or a bird in a tree, use a more shallow depth of field. Doing this will soften the subject’s surroundings and will keep the subject clearly in focus. If you’re looking for as much clarity and sharpness as possible in the entire scene, then use a deeper depth of field. This is usually the case when it comes to landscape photography, but not always. Sometimes I like to frame a landscape in some branches and I want those branches soft. But in general, landscape shots use a deep depth of field. Really though, the sky’s the limit with this type of thing and it’s your own desires and creativity that matters.
I hope I clearly explained the basics of depth of field when it comes to photography. If you have any questions, please let me know in the comment section down below. You can also always ask anything in the photography discussion forum.