Learn How Subject To Camera Distance Impacts Depth-of-Field It's kind of important!

How can I get enough depth-of-field shooting wide open to photograph a large bird? Wouldn't it be necessary to stop down to get the sharp wingtip-to-wingtip shot? Not if the bird is hundreds of feet away. Why? There is a rule that even the most ardent pixel-peeper or measure-beater can’t refute. And this is that rule.

As camera to subject distance increases, depth-of-field increases. Always. Every time. No exceptions. Period.

This is the law. As camera to subject distance increases, depth-of-field increases. Really. Every single time, no matter the camera, the lens, or the subject.

Now let me share with you how this applies. Let's say I am photographing a bird perched 40 yards away and posed against an open sky or the water. The distance between me and the bird is so great that at even with a 300mm lens (M43) wide open at f/4, the depth-of-field covers the entire bird, from wingtip to wingtip, from beak to tail. If the bird was at my minimum close focusing distance - about five feet away, f/4 only provides enough depth-of-field to cover one of the bird's eyes - not the beak AND the eyes. That's because the inverse of this rule is also true. As camera to subject distance DECREASES, depth-of-field also decreases. The next image illustrates that concept.

(Note the killdeer (Charadrius vociferous) picture used above was shot using a 600 mm lens with a maximum aperture of f/4. I attached a 1.4 teleconverter to give me 840mm of focal length. I handheld the camera, laying on the ground and shot at f/8. Even at f/8, the DOF was less than one inch at 26 feet – hence the VERY skinny DOF leaving the photo blurry in front of and behind the bird. FYI there was a big outhouse behind the bird about 100 feet away that just disappeared because of that skinny DOF.)

When you are talking about depth-of-field, the practical reason for this discussion is to discuss the near limit of acceptable sharpness and far limit of acceptable sharpness. In other words, the part of an image that is in focus, front to back, based on the photographer's selected focus point.

When I first got into photography, I was taught that you want to assume that your depth-of-field starts about 33% of the way into the scene (at the focus point) and ends about 66% of the way into the scene (unless you are focused on infinity.)

Turns out that its a popular misconception that depth-of-field is always 33.3% in front of point of focus and 66% behind the point of focus. That is absolutely most often true in the case of standard and wide-angle lenses, and in situations where the subject to camera distance is more than 50 feet, but NOT true at all when you start to shoot with telephoto lenses and/or close subjects. Perhaps the single most neglected factor in these discussions is subject to camera distance. Subject to camera distance and lens focal length impact what the area of acceptable sharpness will be – every time - every single time.

When I shoot with a big telephoto AND I work close – i.e., at the lens close focusing limit (Under five feet in the case of the Olympus 300 f/4 IS Pro Lens) DOF becomes VERY, VERY, VERY thin. In some cases the DOF can be near ZERO! Yep, its true.

But back to my main point. With the big glass, especially when focused at less than 50 feet, DOF is NOT 33/66 – its more like 50/50. With telephoto lenses you get depth-of-field that will be an equal amount in front of and in back of the focus point.

Why does this matter? When shooting landscapes with a wide angle lens for instance, you will often put your main subject in the DOF sweet spot – knowing that you have about 1/3rd in front of the focus point to 2/3rds in back of the focus point with which to find that sweet spot. If you do that when shooting a big telephoto lens, the area of the image that you want highlighted will be wrong. Its 50/50 not 33/66. Is this confusing? Yes it can be confusing. That's why I like to point people to an amazing (and free) resource I found called DOFMaster.

Use DOFMaster to learn more about this subject. It’s worth 10-15 minutes of your time. Here’s how:

Select your camera body. Type in the focal length (mm) of the lens you want to learn about. Select an f/stop, and select the subject distance. Then see what sort of DOF you're going to be working with and what the exact near/far distance will be.

If you do take time to visit DOFMaster, you can prove out every theory I proffer here and do so, instantly.

I am using an Olympus E-PM1 camera for this test. I select a 300mm focal length, an f-stop of f/4 and a subject to camera distance of just five feet. In that scenario, my depth-of-field is a mere 0.01 feet!!!

Remember that as camera to subject distance increases, depth-of-field increases. Type in 120 feet instead of five feet and you’ll see that the DOF moves from 0.1 feet to nearly six feet! Type in 1000 feet and the DOF jumps to more than 400 feet at f/4 but the split moves to a 40/60 split.

These concepts may seem vague but they are important. Over time, if you get to be as old as I am, you eventually learn this stuff and just end up knowing what your DOF will be in most situations. But for now, use this DOF calculator to learn it. And remember the concepts.

If you work at close focusing distance with long lenses you will have razor thin DOF and it will generally be evenly split 50/50. This holds true even at very small apertures.

Don’t take my word for it. Try it for yourself. Set your subject close and then far away. Experiment with depth-of-field and you’ll find out that the rule is reliable. Hopefully moving forward, you’ll be able to take this knowledge and improve your percentage of keepers.


Photo Courtesy Levi Sim

Scott Bourne is President of US Operations at Skylum Software (Formerly Macphun,) an Olympus Visionary and a professional wildlife photographer, author and lecturer who specializes in birds. He was one of the founders of This Week In Photo, founded Photofocus.com and is co-founder of the Photo Podcast Network.

Scott is a regular contributor to several photography related blogs and podcasts and his photography has appeared in more than 200 books and magazines. He is a trainer at both ThinkTapLearn and lynda.com, and is the author of 11 photography books.

Scott is available to speak to your birding group, photography group and for both private and small group bird photography workshops. For more information on engaging Scott as a speaker or workshop leader, or for image licensing and print information, e-mail scott@scottbourne.com.


Copyright Scott Bourne 2017 - All Rights Reserved - scottbourne.com - scottbourne.photography

Report Abuse

If you feel that this video content violates the Adobe Terms of Use, you may report this content by filling out this quick form.

To report a Copyright Violation, please follow Section 17 in the Terms of Use.