Glance at the summary firstThe summary from the end of the lesson, as a road map before you start reading.
The hyperfocal distance is the focus distance at which the back end of the slice of sharpness just touches infinity; when you focus at this distance, sharpness stretches from about half of it to infinity. The distance is found by dividing the square of the focal length by the product of the aperture and the circle of confusion, and it is most useful with wide-angle lenses at medium-narrow apertures. The same idea also serves to catch moving subjects without delay by putting sharpness in a zone in advance; and on a face in the foreground, on every skin, whether it stays inside the near limit of focus is checked by looking at the eyelashes.
Learning goal
You will be able to calculate where to put sharpness in a landscape to keep everything, from the stones in the foreground to the mountains on the horizon, sharp in the same frame. You will explain why focusing at infinity and focusing on the nearest object waste the slice of sharpness; you will find the hyperfocal distance from the focal length, the aperture and the measure of acceptable sharpness; you will use the fact that when you focus at this distance, sharpness stretches from half of it to infinity; you will fix sharpness at this distance by hand on a lens without a distance scale; with the same idea you will catch a moving subject in a zone of sharpness prepared in advance; and you will check whether the face of a person in the foreground, on every skin, stays inside the near limit of sharpness.
The question
On a high pasture, there is a flowery mound in front of you, wooden houses in the middle and rows of mountains behind. To make the mountains sharp, you put sharpness at infinity; in the photo the mountains are sharp, but the flowers in front are a soft blur. This time you put sharpness on the flowers; the flowers are sharp, the mountains a blurry wall.
How does everything from the foreground to infinity become sharp? When you put sharpness somewhere in between, not at random, but at a calculated distance. In this lesson we will talk about how to find that distance, that is the hyperfocal distance, what numbers it depends on, and how it can also be used to catch a subject moving on the street or in the field.
Context
In Lesson 8.3 we saw that sharpness spreads not in a single plane but as a slice: an area in front of and behind the distance you focus at stays sharp, this area widens as the aperture is stopped down, and grows as the focus distance gets longer. We also said that at middle distances the slice stretches further behind than in front. The idea of this lesson comes exactly from this asymmetry.
When you put sharpness at infinity, the back half of the slice spills beyond infinity; since there is nothing to keep sharp there, that half is wasted. When you put sharpness on the nearest object, on the other hand, the slice doesn't reach the horizon. The hyperfocal distance is the focus distance at which the back end of the slice just touches infinity. When you focus at this distance, no part of the slice is wasted, and the sharp area stretches as close as possible.
Simple explanation
What counts as sharp?
The image of a point is truly a point only in the plane of focus; as it moves away from the plane, it turns into a small spot, a circle. This circle is called the circle of confusion. If the circle is small enough, the eye still sees it as a point, and that area counts as sharp. Acceptable sharpness is the largest size at which this circle keeps looking sharp.
This limit isn't a constant given by nature but an agreement: it changes with how big the photo will be and from how far away it will be looked at. Many tables and calculators take a circle of about 0.03 millimeters for full-frame sensors; this value was chosen with a medium-sized print looked at from normal reading distance in mind. On cameras with small sensors a smaller circle is used, because the image will be magnified more. If you are going to look at the photo magnified pixel by pixel on a screen, or print it the size of a wall, this limit may feel loose to you.
How is the hyperfocal distance calculated?
The calculation relies on three numbers: the focal length, the aperture and the circle of confusion. The hyperfocal distance is found, approximately, by dividing the square of the focal length by the product of the f-number and the circle's size. On a full-frame camera, with a 24-millimeter lens and an aperture of f/8, the calculation goes like this: twenty-four times twenty-four makes five hundred seventy-six; eight times 0.03 makes 0.24; when you divide five hundred seventy-six by 0.24, you get about two thousand four hundred millimeters, that is a distance close to two and a half meters.
When you focus at this distance, sharpness starts from about half of it, that is about one meter twenty centimeters in front, and stretches to infinity. When you stop the aperture down to f/11, the hyperfocal distance drops to one meter seventy-five centimeters, and sharpness starts from about ninety centimeters. As the focal length grows, the hyperfocal distance grows quickly: at 50 millimeters and f/8 it passes ten meters. That is why the hyperfocal distance is most useful with wide-angle lenses. You don't have to do the calculation by hand every time; many depth of field calculators written for phones do the same job in seconds.
How is it applied on a lens?
On an old or manual lens with a distance scale, the job is easy: you turn the ring and match the distance you calculated against the mark on the scale. Some lenses also have depth of field marks drawn for f-numbers; when you bring the infinity mark to the f/11 line on one side, the f/11 line on the other side shows the distance where sharpness begins.
On a lens without a distance scale, on the other hand, you find an object standing at the distance you calculated: a stone two and a half meters away, a fence post, a bag you put on the ground. You can roughly measure this distance by counting your steps. You focus on that object with autofocus, then switch focus to manual, or lift your thumb from the back button; sharpness stays fixed at that distance. Now you can set up the frame as you like. This fixing is another use of the manual focus and back-button focus we talked about in Lesson 10.5.
Where does the calculation mislead, and what is it good for with a moving subject?
The calculated limits aren't sharp lines, but the places where acceptable softness begins. If you are going to print the photo large, a common way to leave a margin is to focus a little farther than calculated, or to stop down one more step. But stopping down has a limit: at very narrow apertures such as f/16 and f/22, diffraction slightly softens the whole frame and takes back part of the depth of field you gained. A narrow aperture also lengthens the shutter speed; in dim evening light a tripod may be needed.
The same idea is also a way to catch a moving subject. This is called zone focusing: you put sharpness at a distance in advance, stop the aperture down enough to keep the sharp area wide enough, and shoot as the subject passes through this zone. Because the camera isn't searching for sharpness, there is no delay at all. For people walking on the street, a cyclist passing along the village road, a running child, this gives a sharp frame even in moments autofocus can't follow.
If there is a person in the foreground, check whether their face stays inside the near limit of focus. On a face standing close to the limit, softness shows first in the finest details, the eyelashes and the strands of hair. On dark skin buried in evening shadow, as on light skin shining in noon sun, these details are low in contrast already, and the limit is easily missed. After the shot, magnify the face and look at the eyelashes; if they are soft, move the person one step back or stop the aperture down one more step.
Visual evidence
You go back to the high pasture. You have put the 24-millimeter lens on your full-frame camera. In the foreground, a meter and a half away, an elderly dark-skinned shepherd is sitting on a stone; in front of them are purple flowers, behind them houses and mountains. You set the aperture to f/11; the calculation tells you to put sharpness at about one meter seventy-five centimeters. You focus on a fence post two steps away and switch focus to manual. The sun is about to set, and because the shutter speed has lengthened, you mount the camera on a tripod.
When you magnify the photo, the petals of the flowers in front, the stitching of the shepherd's cap and the lines of their wrinkled hands are sharp. You look at their eyelashes; they can be made out too, because the shepherd is well behind the near limit of focus, at around ninety centimeters. The wooden shutters of the houses in the middle and the single pine trees on the ridge of the farthest mountain are sharp too. When you take the same frame with sharpness at infinity, the mountains are sharp again, but the flowers and the shepherd's hands have softened. The same lens, the same aperture; the difference was the distance where sharpness was put.
Common mistakes
Common mistakePutting sharpness at infinity in a landscape.
The back half of the sharp area spills beyond infinity, and the foreground softens. The fix: calculate the hyperfocal distance and put sharpness there.
Common mistakeStopping the aperture down to its narrowest value to keep everything sharp.
Diffraction softens the frame and the time lengthens. The fix: work with the hyperfocal distance and stay at a medium-narrow aperture.
Common mistakeAssuming a face in the foreground is inside the near limit of focus.
On a face close to the limit, the eyelashes and strands of hair soften first. The fix: magnify the face and check; if needed, move the person back or stop down one more step.
Summary
The hyperfocal distance is the focus distance at which the back end of the slice of sharpness just touches infinity; when you focus at this distance, sharpness stretches from about half of it to infinity. The distance is found by dividing the square of the focal length by the product of the aperture and the circle of confusion, and it is most useful with wide-angle lenses at medium-narrow apertures. The same idea also serves to catch moving subjects without delay by putting sharpness in a zone in advance; and on a face in the foreground, on every skin, whether it stays inside the near limit of focus is checked by looking at the eyelashes.
Mini assignment
In this assignment you will use the hyperfocal distance both in a landscape and, in the module project, on a moving subject.
- With a wide-angle lens, photograph a scene with a near object in front and a distant landscape behind three times at the same aperture: with sharpness at infinity, on the nearest object, and at the hyperfocal distance you calculated.
- On a lens without a distance scale, focus on an object standing at the distance you calculated, fix the focus, and set up the frame afterward.
- Module project: photograph a running child, a dog or a cyclist sharply, either by putting sharpness in a zone in advance or by following with continuous focus; count which method gives more sharp frames.
- In a landscape with a person in the foreground, shoot while moving the person closer to and farther from the near limit of focus, and find at what distance the eyelashes soften.
Check yourself
- In the frame where you focused at the hyperfocal distance, are both the foreground and the horizon sharp?
- Among the frames you took of the moving subject, are more than half sharp at the eye or face?
- Did the eyelashes of the person in the foreground, regardless of skin tone, stay sharp inside the near limit of focus?
Glossary
| Term | Short definition |
|---|---|
| Hyperfocal distance | The focus distance at which, when you focus there, the back end of the slice of sharpness just touches infinity. |
| Acceptable sharpness | The limit of sharpness at which the blur circle still looks like a point to the eye. |
| Circle of confusion | The small spot that a point outside the plane of focus forms in the image. |
| Near limit of focus | The end of the sharp area closest to the camera; at hyperfocal focus it is about half of that distance. |
| Zone focusing | The method of putting sharpness at a distance in advance and shooting as the subject passes through that zone. |
Mini quiz
1. Why does putting sharpness at infinity in a landscape soften the foreground?
- A) Because the aperture opens by itself when you focus at infinity
- B) Because the back half of the sharp area spills beyond infinity and is wasted
- C) Because ISO rises at infinity focus
- D) Because the foreground always comes out blurry
2. On a full-frame camera at 24 millimeters and f/8, with a 0.03-millimeter circle, about how far is the hyperfocal distance?
- A) About 60 centimeters
- B) About 10 meters
- C) About 2.4 meters
- D) Infinity
3. When you focus at the hyperfocal distance, where does the sharp area begin?
- A) At about half of that distance
- B) Exactly at that distance
- C) Right in front of the camera
- D) At twice that distance
4. If the eyelashes of a dark-skinned person sitting in the foreground have softened at the near limit of focus, what do you do?
- A) Change the white balance
- B) Put sharpness at infinity
- C) Shorten the shutter speed
- D) Move the person one step back or stop the aperture down one more step
Answers
- B — Beyond infinity there is nothing to keep sharp; that half of the slice isn't used, and the near end doesn't reach the foreground.
- C — The square of twenty-four is five hundred seventy-six; divided by 8 × 0.03 = 0.24, it comes to about two thousand four hundred millimeters.
- A — At hyperfocal focus, sharpness stretches from about half the focus distance to infinity.
- D — Moving the person behind the limit, or stopping down to bring the limit closer, puts the eyelashes back into the sharp area.
Summary card
- Don't focus at infinity: half of the sharp area is wasted.
- Hyperfocal ≈ square of the focal length ÷ (aperture × circle of confusion).
- Focus at hyperfocal, and sharpness stretches from half that distance to infinity.
- No scale? Focus on an object at that distance, then fix it.
- Catch moving subjects without delay with zone focusing; on a face in the foreground, on every skin, look at the eyelashes.
Bridge to the next lesson
In the high pasture frame, everything from flower to mountain is sharp. But imagine taking that photo before the sun sets and twenty minutes after it has set: the same flowers, the same houses, the same shepherd's face, wrapped in an orange warmth in the first and a bluish coolness in the second. Does light have a color, and by what does the camera record that color? The next lesson begins with color temperature, which measures the color of light in Kelvin.