I’ve written about depth of field as it relates to photography before on this website, so I won’t rehash all that I’ve already covered here. What I would like to do instead is expand upon what I’ve discussed and move towards a more refined level of photographic planning. If you’re a still life or portrait photographer, you’ll want to read this. This is important stuff.
When taking photos of objects that are fairly close to your camera, you’ll definitely need to contend with blur. Depth of field. Out of focus. Whatever you want to call it. The closer you get to an object, the more blur you’ll see in front of the object as well as in back of it. It’s as if this blur is magnified the closer you go. If you were outside taking landscape shots, blur caused by a large aperture wouldn’t be nearly as intrusive as it can be when you’re inside. The window where objects remain sharp gets larger the farther you move away from them.
In today’s post, I’d like to offer you a very handy tidbit of information that will greatly assist you when it comes to determining exactly how large or small that sharp window (depth of field) will be. Depending on what type of camera you have, what your aperture size is, what your focal distance is and how far you are away from the object you’d like to photograph, you can actually calculate how much of your subject will be in focus and how much of it won’t be. If you’re new to photography or even a well seasoned amateur, this may come as news to you. I think that once you learn this concept, you’ll have a new “focus” on where you position yourself and your camera as well as what settings you use. This is all fun stuff, so read on below.
A Quick Reminder of What Depth of Field Is
Okay, fine. I’ll do it. I’ll remind you of what depth of field is, just in case someone new to this website is reading today. Depth of field is the point that is closer to you to the point that is farther away from you that is sharp in a photograph. So if you’re standing there with your camera in hand, taking a photo of someone who is facing you, depending on your camera settings, there may be some blur in front of them and some behind them. Depth of field is the distance of sharpness in between those two blurs. If this concept is completely foreign to you, I highly encourage you to read my previous post on the topic.
How to Calculate Depth of Field
Since I’m fairly certain that there are very few people on earth who want or need to know the actual depth of field calculations as they relate to photography, I’ll skip the numbers. If you are one of the few, you can find them here. Let me warn you though, they are extraordinarily boring and there are many different calculations, depending on many different factors. Personally, I use either online depth of field calculators or apps that can easily be downloaded and used on tablets and smart phones. For most photographers, there’s no sense in pulling out a pencil and paper while attempting to engage in some marvelous photography.
I found two different only calculators that might be helpful to you. The first is called DOFMaster and the second is from PhotoPills. Both of these services do the trick. If you’d like to find your own service, simply search for “Depth of Field Calculator.” It’s that easy.
Some Calculation Examples
In this section, I’d like to go over some very realistic examples of what some of these types of calculations might look like. Let’s say that you’ve got your camera set up on a tripod that’s next to a table and on top of that table, you have a small figure that you’re photographing. I’ll give you some specs and then the results of the calculations. Here goes:
Focal Length: 55mm
Aperture Setting (F-Stop): F/16
Subject Distance: 2 Feet
Near Limit: 1.89 Feet
Far Limit: 2.12 Feet
Total DOF: 0.22 Feet
In Front of Subject: 0.11 Feet (47%)
Behind Subject: 0.12 Feet (53%)
Okay, so the above information describes a situation where you’ve got a camera that’s two feet away from the object on the table. This is actually the distance from the camera’s sensor to the object. You’ve got your lens set to 55mm, which is the actual focal length, not the converted focal length for your sensor size. Most of these calculators take your camera model into account, so you won’t need to do any conversion. Finally, you have your aperture set to F/16.
Here are the results. The “near limit” is 1.89 feet. This means that this is the distance from your camera to the very closest spot in your scene that is acceptably sharp. Everything between your camera and this point will be blurry. The “far limit” is much like the near limit. It’s different though, of course. The far limit is 2.12 feet and it’s the distance from your camera to the farthest spot that’s acceptably sharp. So from your camera to the near limit is blurry (in front of the subject). Then you’ve got the area that’s sharp (the area surrounding the subject) and then you’ve got the far limit, which is the beginning of the blurry area behind the subject. The area surrounding the subject that’s sharp is called the total depth of field. In this case, it’s .22 feet, which isn’t a lot. This happens to be a very shallow depth of field.
And finally, because we’re fancy like that, we’ve got the percentages of the the distances from the focus plane to the near limit and the far limit, respectively. In this case, they are 47% and 53%.
What I’d Like to Emphasize
You can head into one of the calculators and punch in numbers all day long to get a feel of how the different variables affect depth of field. What I’d like to impress upon you in this final section is how much the distance between your camera and the subject you’re photographing can truly impact the acceptable sharp area. It’s pretty crazy.
I’m going to to keep all the variables the same from my example above, except the distance between the camera and the subject. If I change the distance from two feet to six feet, the depth of field increases from .22 feet to 2.21 feet. Now, if I increase the distance to 20 feet, the depth of field jumps all the way to 38.5 feet. That’s quite impressive.
The reason I mention this is because it’s quite common for people to associate depth of field with aperture size. While that’s a very good measure and while I’m not discounting it in any way, I’d like to just remind you that distance between your camera and the subject you’re shooting can have a profound effect on depth of field as well. I just want you to keep that in mind as you’re shopping for lenses and thinking about what type of photography you mostly engage in.
Well, I hope I clearly explained how you can calculate depth of field as it pertains to photography. As you’re engaging in this hobby or profession, it’s helpful to know exactly how much sharp area you’re dealing with, so these calculators can prove invaluable. If you have any questions regarding this post or topic, please ask down below in the comment section. If you have anything to add or further questions, you can always participate in the photography use’s forum. Thanks for reading!