The One-Third Myth

Don't fall prey to this hyperfocal nonsense

You've seen those pictures with a sharp foreground - maybe some flowers - and an in focus background - like a mountain. These are usually made with wide angle lenses with the foreground very close to the camera, usually within a foot or two.

Getting everything in focus is done with a technique called hyperfocal focusing, which is basically focusing the lens at a point so that depth of field extends from that focus point toward the camera and away from that point towards the background. Enough so that everything appear in focus.

The big question I always get is: Where should I focus?

There's a rule of thumb out there that says to get everything in focus, set your aperture to f/22 and focus a third of the way into the frame. The idea is that you need to focus beyond your foreground so that the range of depth of field will cover the entire frame. This is true. That's the concept of hyperfocal focusing. But the advice to focus one-third into frame should be tossed onto the junk pile.

Think about it. One-third of the way into the frame. Is that one-third of the way up the frame or one-third of the way into the scene? And depending on your composition, that one-third spot, no matter how you determine at it, can vary wildly.

If you truly want to correctly use the hyperfocal technique, you need to embrace your inner geek a little more than just memorizing that one fraction.

The best way I know to determine the proper focus point is to use a hyperfocal chart. I've written about that before and you can read all about it here.

But if you don't like charts, or you forget yours, or you just don't want to mess with it, there is a better rule of thumb than "focus one-third of the way in." This is based in the reality of your composition and how far away your foreground happens to be.

First of all, if you need a lot of depth of field I hope you already know to be using a small aperture opening like f/16 or f/22.

The most effective and accurate rule of thumb I've heard is to focus at twice the distance of your foreground object. So say that your foreground is a bunch of pretty flowers that are about two feet in front of your camera measured from the focal plane (your sensor). You would then focus at four feet. You can either use the focusing scale on your lens or focus on something that's four feet away.

This will often work very well, but much still depends on focal length and aperture, which a hyperfocal chart will take into account. Say for instance you're using a 24mm lens on a full-frame sensor camera. Even at f/22, if your foreground is a foot away and you focus at two feet, your foreground will probably be in focus, but you'll sacrifice sharpness in the background. That's just the physics of the thing (or as some would say, arithmetic).

So if you try this technique, I suggest you also try bracketing your focus point a little. First focus at twice the distance of your foreground, then take a shot focusing just a little farther away and a shot focused just a little closer. Study the results and pretty soon you'll have a feel for what your lens is capable of.

But please, don't take seriously the advice of simply focusing a third of the way in. Oh, that way madness lies.

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3 responses to “The One-Third Myth

  1. Great advice Rod. It has always seemed to me that the “1/3 of the way into the frame” rule sounded easy but required too much interpretation to be reliable. Nice to know I need not worry about trying to figure it out. Too bad “hyperfocal” sounds so intimidating, because it isn’t difficult.

  2. There’s a potential future solution with the rise of EVF (electronic viewfinder) D-SLRs: focus peaking, which allows you to see in the viewfinder which areas are in sharp focus (on my A77, objects in focus show up with a yellow outline). When combined with DoF preview and manual focusing, finding the hyperfocal distance is wonderfully easy.

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