Understanding Hyperfocal Distance

If you’re familiar with depth of field, you know that it’s a great creative tool for photographers. By manipulating DoF in your images, you can focus attention on a specific point in a shot or treat your audience to a view that’s beautifully sharp from the foreground to infinity.

The latter of these two is often, though not always, the desired effect in landscape and architectural photography. Regardless of the genre, when you want to achieve sharpness throughout the greatest range possible in a photo, hyperfocal distance is the key. Before we define that term, let’s examine why it’s important.

Why a Narrow Aperture Isn’t Enough

In our article on aperture, we explained that depth of field may be envisioned as a range of sharpness that varies with aperture size. Rather than existing at a fixed distance from the lens, however, this area of sharpness moves in relation to the focal point you choose.  Focus on a point farther away from the camera and the closest sharp point moves away, too.

By focusing too far away, your foreground may not be as sharp as you like. Focus too near the camera and the sharpness may drop off too soon, leaving distant objects blurred. Therefore, simply selecting a narrow aperture doesn’t guarantee that the result will be an image with maximum depth of field.

The Sweet Spot

It’s also important to understand that due to diffraction, using the smallest or largest available aperture sizes on a given lens can actually reduce the overall sharpness of an image. Every lens has a “sweet spot” in its aperture range, where the best sharpness is achieved.

Given these facts, you can see that producing the maximum sharpness in a photo relies on two factors:

1. Selecting an aperture that gives you the greatest depth of field without causing diffraction
2. Setting your focus to the closest possible distance while maintaining acceptable focus at infinity

That focal point for a given aperture setting and a given focal length is the hyperfocal distance.

The Definition

Hopefully, that lengthy explanation above will help you grasp the definition of hyperfocal distance. It is, simply, the closest possible point to the focal plane of the camera that can be focused on while still maintaining acceptable sharpness at infinity. If it suits your purposes better, you can also think of it as the closest point that will be in focus when a lens is focused at infinity.

Because depth of field varies with aperture size and focal points vary with focal length, hyperfocal distance calculations are based on both of those factors. Since sensor size also affects depth of field, it also factors in.

Calculating the Distance

Okay, let’s look at the formula to determine the hyperfocal distance for a particular lens at a particular aperture setting:

H=(f^2/Nc) +f

Where:

H = hyperfocal distance

f = focal length

N = f-number

c  = the circle of confusion limit

“Wait, what?”  You’re right; We sort of threw you a curve there. Not only is it a fun little mathematical puzzle, there’s a new term there. The circle of confusion is a measurement of how well a lens focuses light rays. That’s not much help, is it? Neither is this geometrical representation:

©Cmglee – shared via CC BY-SA 3.0

Let’s face it, we’re photographers, not mathematicians. What’s more, the work has already been done for us. If you’re really intent on learning to calculate it yourself, We’d recommend starting here. Otherwise, let’s try a different approach so you can start using this focusing tool.

The Easy Ways

Thanks to those clever mathematicians, you can use a hyperfocal distance chart or calculator to calculate both DoF and hyperfocal distance. You can also use an app for your mobile device or computer. There are a number of good ones available, so search your app store. DOFMaster offers a good selection of free printable charts and apps for most operating systems.

Courtesy of DOFMaster.com

One of the easiest ways to find the hyperfocal distance for a given aperture may be available on your lens. If it’s equipped with a depth of field scale like the one pictured below, there’s a clever way to set your focal point with no calculation at all.

Note how the infinity mark on the lens above is aligned with the 8 on the DoF scale. This lens is focused at the approximate hyperfocal distance for f/8. This lens also happens to have a hyperfocal scale at the top. You’ll notice that the 8 on that scale aligns with the center focus mark, confirming the setting. 

This method can be used to focus at the hyperfocal distance for an aperture setting on any lens with a depth of field scale. Pretty simple, don’t you think?

Theory vs. Reality

You can probably see that the DoF scale method above isn’t perfect. That’s alright, because the practical application of hyperfocal distance isn’t really an exact science. In fact, using a scale or calculator probably isn’t going to be accurate to a few millimeters, either.

Consider this: How often do you use a measuring device to determine how close to the focal plane of your camera your point of focus is? Chances are, you simply estimate the distance if you think about it at all. That’s what the rest of us do, too. It’s all about approximation.

The Other Direction

Before wrapping up this post, there’s one more point that should be considered. You’ll recall that the second definition listed above involved focusing at infinity. You can apply that method as well, by focusing at infinity, then ensuring that the closest item you want to be sharp is at or beyond the hyperfocal distance for the aperture setting. Use the method that works best for you.

Go Forth and Sharpen!

With this basic understanding of hyperfocal distance, you should find it easy to maximize the range of sharpness in your photos. Try it out and see the improvement for yourself!