Photography 101

Part 2: Focus and depthChapter 10

Tools

Contents

Part 1: Exposure

  1. 1 Mastering the Exposure TriangleBalance aperture, shutter speed and ISO for brightness, depth, motion and noise.
  2. 2 ISO and image noiseWhen to raise ISO, why grain appears, and how to trade it for a faster shutter.
  3. 3 MeteringWhat the meter aims for, how to read it, the four metering modes, and Sunny 16 when there's no meter.
  4. 4 Shooting modes and the histogramLet the camera set one setting, steer it with exposure compensation, and check the result with the histogram and zebras.
  5. 5 Dynamic rangeHow many stops a camera can hold at once, what to keep when a scene is wider, and measured figures for real cameras.
  6. 6 Shutter speed and motionCamera shake, freezing or blurring a moving subject, and ND filters for long exposures.
  7. Part 1 cheat sheetFormulas and starting settings from chapters 1–6.
  8. Part 1 quizCheck yourself on chapters 1–6.

Part 2: Focus and depth

  1. 7 Camera LensLens anatomy and how to choose wide, standard, telephoto, prime, zoom and specialist lenses for real subjects.
  2. 8 Aperture and depth of fieldWhy a wider aperture blurs the background, what else controls blur, and the shape of bokeh.
  3. 9 Sensor size and crop factorWhat a smaller sensor crops, equivalent focal length and aperture, and why phones fake the blur.
  4. 10 Hyperfocal distanceSharp from here to infinity: focusing landscapes with blur circles, focus stacking and a cheat card.
  5. 11 Diffraction and the sharpest apertureWhy f/22 looks soft, where your lens is sharpest, and how pixel size changes it.
  6. Part 2 cheat sheetFormulas and starting settings from chapters 7–11.
  7. Part 2 quizCheck yourself on chapters 7–11.

Part 3: Composition

  1. 12 The composition reading planAll 15 chapters of The Elements of Composition, with printed page numbers and a photography lesson for each.
  2. 13 Introduction to compositionComposition as visual communication: choose what to show, compare three frames, and see how viewers read them.
  3. 14 What is composition?Arrange subject, space and edges to change what a photograph says; compare photos and make three versions of one scene.
  4. 15 Focal pointsChoose where the eye lands first, use contrast and space to build a visual path, then test thirds and diagonals in a field exercise.
  5. 16 LinesFollow straight, curved and implied lines through a photograph, then make three frames of one subject from different positions.
  6. 17 ShapesFind shapes made by subjects and space, use a frame within the frame, and compare three ways to place one subject.
  7. 18 TexturesMake a surface feel tangible with light, detail and context, then photograph one material three ways.
  8. 19 PatternsUse repetition to build rhythm, break a pattern to draw attention, and make three versions of one repeated scene.
  9. 20 SpaceUse positive and negative space, fill the frame, and simplify without losing meaning.
  10. 21 DepthLayer foreground, middle ground and background, and use perspective or deep space to show distance.
  11. 22 BalanceWeigh elements with symmetry, asymmetry and radial arrangements; explore the golden ratio as an optional guide.
  12. 23 ContrastCreate meaning and focus through contrasting subjects, light, shadows and colour.
  13. 24 ColorChoose hue, saturation and brightness, then compare complementary, triadic, analogous and monochromatic palettes.
  14. 25 ToneRead shadow, midtone and highlight; shape global and local tone while keeping meaningful detail.
  15. 26 AngleChange camera height and tilt to compare level, straight up or down, high and low viewpoints.
  16. 27 Composition conclusionBring the elements together in a four-frame story and develop your own way of seeing.

Part 4: Color Theory

  1. 28 Color Theory in PhotographyUse HSL, warm and cool depth, four color harmonies, white balance and selective editing to guide attention.
  2. 29 White balanceRead the color of light, match Kelvin and tint, and choose what to preserve when lights mix.

Tools

  1. Color wheelExplore hues, adjust saturation and luminosity, enter RGB or hex values, and preview the color live.
  2. Photo editorTry light, colour, detail and crop adjustments on a sample or your own photo, then save the result.
  3. Golden hour plannerSunrise, sunset, golden hour and blue hour for where you are, and where the sun rises and sets.
  4. ND filter calculatorYour shutter speed with an ND filter on, and a countdown timer for bulb mode.
  5. Depth of field calculatorHow much is sharp for your lens, aperture and focus distance, and the hyperfocal distance.
  6. Photo info and location removerSee a photo's camera settings and where it was taken, then remove the location before you share it.

Chapter 10Part 2: Focus and depth

Sharp from here
to infinity

Hyperfocal distance confuses almost everyone at first, because it's usually explained with formulas instead of what is physically happening. Move the focus below and watch the blur circles on the sensor grow and shrink.

Blur circle lab

Far right is infinity.

1/3 stop per step.

The mountain stays at infinity.

Sensor

The landscape

Blur circles on the sensor

Limit 0.03 mm

Rock Focus point Mountain (∞)

Dashed ring: the largest blur circle that still looks sharp. Green is inside it; amber is too big.

Sharp zone

Sharp from

Near limit
Far limit
Hyperfocal (H)

What's physically happening

Normal focus

Suppose you're photographing a person 3 m away, with a mountain 100 m behind them. You focus on the person.

Camera Very close soft Person, 3 m perfectly sharp Mountain, 100 m slightly soft

Hyperfocal focus

Instead of focusing on the person, you focus farther away, at the hyperfocal distance H. Here H is 10 m.

Camera 5 m (H/2) sharp from here 10 m (H) focus point ∞ still sharp

When focused at H, infinity is "just sharp enough", and everything from H/2 to infinity appears acceptably sharp. With H at 10 m, that is everything from 5 m to the horizon.

A real example

A 24 mm lens at f/11 on a full-frame camera has a hyperfocal distance of about 1.7 m. Focus at 1.7 m, and everything from about 0.85 m to infinity looks sharp. A rock 1 m away and a mountain 10 km away both appear sharp.

This is why landscape photographers love hyperfocal distance.

0.85 m sharp rock, 1 m 1.7 m focus ∞ sharp (mountain)

Seeing it as blur circles

Imagine the sensor tolerates a tiny blur circle. Anything that lands on the sensor as a circle smaller than that limit looks sharp to your eye.

Object at 10 m Lens Sensor
Focused at 10 m, object at 10 m. The rays meet exactly on the sensor: a tiny point, perfectly sharp.
From infinity rays cross here Lens Sensor
Focused at H, object at infinity. The rays cross just before the sensor and land as a tiny blur circle. It is small enough that your eye sees it as sharp.

Hyperfocal is chosen so the blur circle from infinity is exactly at the acceptable limit. The mystery is really just controlling how large those blur circles are on the sensor.

Why does H/2 appear?

When focused at H, objects beyond H create a tiny blur, and objects closer than H create a tiny blur too. The maths works out so the nearest acceptable point lands at H/2.

You can check it: the near limit is (H − f) × s ÷ (H + s − 2f) for a focus distance s. Put s = H and it simplifies to exactly H/2.

What hyperfocal is not

Many people think "hyperfocal means maximum sharpness." Not true. The sharpest point is always the focus point.

Hyperfocal is the focus distance that gives the largest depth of field while still keeping infinity acceptably sharp.

Calculating it

H = f2 ÷ (N × c) + f

f is the focal length, N the f-number and c the circle of confusion: the largest blur circle that still looks sharp. This page uses 0.03 mm, a common value for full-frame sensors.

For a 50 mm lens at f/8:

50² ÷ (8 × 0.03) + 50 ≈ 10,467 mm ≈ 10.5 m

Sensor size, and why charts disagree

Smaller sensors are enlarged more for the same print, so they use a smaller c, about 0.03 ÷ crop factor. With the focal length held fixed, this pushes H farther: a 28 mm lens at f/16 on a 1.6× crop camera uses c ≈ 0.019 mm, giving about 2.6 m. But to keep the same framing you usually choose a shorter lens. At f/11, 24 mm on full frame gives H ≈ 1.77 m, while a similarly framed 16 mm on 1.5× APS-C gives H ≈ 1.18 m. See the sensor and viewing-size explanation.

The acceptable blur is a convention, not a law of physics. Published charts and apps use anywhere from 0.019 to 0.03 mm for full frame, so their numbers differ. A 100 mm lens at f/16 gives 20.9 m with 0.03 mm, but about 33 m with 0.019 mm.

What moves it

Focal lengthAt f/8At f/16
24 mm2.42 m1.22 m
50 mm10.47 m5.26 m
70 mm20.49 m10.28 m

Stopping down brings it closer: one stop divides it by about 1.4, and two stops (f/8 to f/16) halve it. Zooming in pushes it much farther, because the focal length is squared. At the same focal length, a stricter sharpness standard (a smaller c, for big prints or smaller sensors) also pushes it farther.

In the field

Tips

  • If in doubt, focus a little beyond H, not short of it. Short of H, infinity turns soft. A little beyond costs only a little near sharpness.
  • If the farthest thing is closer than infinity, a treeline for example, you can focus slightly closer than H and gain more foreground.
  • Check on the camera. Zoom into the playback image at the nearest and farthest points. It is not always possible to get everything sharp.
  • Focusing at infinity wastes depth of field. The near limit then sits at about H instead of H/2.

Try it in the lab

  1. Press Focus on the rock. The rock is sharp, but the mountain's blur circle is too big.
  2. Press Focus at infinity. The mountain is sharp, but the near limit sits at H, so the rock turns soft.
  3. Press Focus at hyperfocal. Both blur circles fit inside the limit, and the sharp zone runs from H/2 to ∞.
  4. Open the aperture to f/4, or zoom to 70 mm, and watch H move far away.

The lab holds the lens focal length fixed when you change sensors, so the framing would change on a real camera. It uses the thin-lens model with a circle of confusion of 0.03 mm ÷ crop factor. The scene is an illustration whose blur follows the calculation. Real lenses also have aberrations and diffraction, which this ignores.

When hyperfocal isn't enough: focus stacking

A flower 35 cm from a 24 mm lens and mountains on the horizon can't both be sharp in one shot at f/8: hyperfocal only reaches down to 1.2 m. Stopping down to f/22 brings it to about 0.45 m, but diffraction softens the whole picture. Instead, take several photos focused at different distances and merge the sharp parts.

Shot 1, focus 0.4 m Shot 2, focus 0.55 m Shot 3, focus 0.9 m Shot 4, focus 2.4 m (H) Merged 0.3 m0.6 m1 m2 m∞

How to shoot it

  1. Put the camera on a tripod and switch to manual focus and manual exposure, so nothing changes between shots.
  2. Focus on the nearest thing and take a photo. Turn the focus ring a little farther and take the next one.
  3. Keep going until you reach the hyperfocal distance. Each sharp zone should overlap the one before.

Merging the photos

Software lines up the photos and keeps the sharpest part of each: Photoshop (Auto-Blend Layers), Affinity Photo, Helicon Focus or Zerene Stacker.

Many cameras can take the series for you. Look for focus bracketing or focus shift in the menu. Wind or moving water between shots makes ghosts, so it suits still scenes.

Hyperfocal cheat card

Pick your sensor and print this card, or save it to your phone. Each cell is the hyperfocal distance: focus there and everything from half that distance to the horizon is sharp. Use the focal length marked on the lens.

Hyperfocal distances

Lensf/8f/11f/16

Focus at the distance shown; sharp from half of it to infinity. Photography 101, photography101.codekunda.com