Focus
Written by Abin Alex and Anu Joseph.
Abstract
Focus is the point where light from the subject meets exactly on the sensor, so that part of the picture is sharp. This guide describes the types of focus used in film, the working of autofocus, focus modes and focus points, the effect of aperture and light on autofocus, and manual focus and focus pulling. It also treats hyperfocal distance and the one-third rule, and it lists suitable focus settings for each kind of photography. It is written for photographers and cinematographers.
Keywords: focus; autofocus; manual focus; focus pulling; hyperfocal distance
- What is focus?
- What are the types of focus in filmmaking?
- How does autofocus work?
- What are the focus modes?
- What are focus points and AF area modes?
- How do aperture and light affect autofocus?
- How do I focus by hand and lock focus?
- How does focus pulling work?
- Where should I focus: hyperfocal distance and the one-third rule?
- Which focus settings suit each kind of photography?
What is focus?
Short answer. Focus is reached when the light rays from a point on the subject meet exactly on the sensor, so that point is recorded sharply. The camera does this by moving lens elements, which changes the distance between the lens and the sensor.
- A point of the subject is in focus when its light rays meet on the sensor plane. A point that is nearer or farther than the focused distance is recorded as a small blur circle.
- Focus is closely related to sharpness. The aperture and the depth of field then decide how much of the scene in front of and behind the focused distance also looks sharp.
- The lens moves its focusing elements to match the distance of the subject. Moving them can also bring small lens aberrations, where rays from one point do not meet at a single point.
- In 1839 the Paris magazine Charivari joked that a small focusing error with Daguerre's new process could give you a portrait of a parrot, a watering pot or a vase instead of your wife.
Cham tipDecide what the viewer must see sharp before you press the shutter.
Cham taskPhotograph one object from the same spot three times, focused on the front, the middle and the back. Compare the pictures.
Check yourself: A portrait has sharp ears and soft eyes. What went wrong?
The focus point sat on the wrong part of the face, or the focus plane fell a little behind the eyes. Refocus on the nearer eye.
What are the types of focus in filmmaking?
Short answer. Filmmakers use six kinds of focus to shape what the audience sees: deep, shallow, soft, rack, split-diopter and tilt-shift focus. Each one controls which parts of the frame are sharp and which are not.
- Deep focus keeps the foreground, middle ground and background sharp together. It usually means a small aperture, about f/8, f/16 or f/22, and often a wide lens. Citizen Kane (1941) is the standard example.
- Shallow focus keeps only one part of the frame sharp. It comes from a wide aperture, a longer focal length or a closer camera, and it draws the eye to one place and suggests closeness and feeling.
- Soft focus makes the whole frame slightly blurred or glowing. It needs a special lens or a filter, and it often marks a dream or a memory.
- Rack focus changes the focus during one shot and moves the sharp plane from one subject to another. The shallower the depth of field, the more obvious the change.
- A split diopter is a half lens fixed in front of the main lens. It lets two subjects at different distances look sharp in one shot, with a soft gap between them.
- A tilt-shift lens can tilt, which changes the plane of focus (the Scheimpflug principle), and shift, which changes perspective without changing focus. Shift is used to correct converging vertical lines.
- Deep focus is not the same as depth of field. Depth of field measures how much of the picture is sharp. Deep focus is the look you get when all of it is sharp.
| Type | What is sharp | How it is made | Typical use |
|---|---|---|---|
| Deep focus | Everything | Small aperture, wide lens | Show space and the relation between people |
| Shallow focus | One part | Wide aperture, long lens, close camera | Isolate a face or an object |
| Soft focus | Nothing fully sharp | Special lens or filter | Dreams and memories |
| Rack focus | Changes during the shot | Focus pull | Move the viewer's attention |
| Split diopter | Two distances at once | Half lens in front of the lens | Two subjects in one shot |
| Tilt-shift | A tilted plane | Tilting the lens | Miniature look, perspective control |
Table 1. Types of focus.
Cham tipChoose deep or shallow focus for a reason: to show space, or to direct attention.
Cham taskShoot the same scene at f/2.8 and at f/16. Write one line on what each picture tells the viewer.
Check yourself: Is deep focus the same as depth of field?
No. Depth of field measures how much of the picture is sharp. Deep focus is the look you get when all of it is sharp.
How does autofocus work?
Short answer. Autofocus either measures the distance to the subject or looks for the sharpest image, and then drives the lens to match. Active systems send out their own signal. Passive systems only analyse the light that comes through the lens.
- Active AF sends a sonar or an infrared signal to the subject and reads the reflection to find the distance. It was used in the early autofocus cameras.
- Canon's AF35M, marketed from November 1979, used a near-infrared beam and a receiving diode, and it could focus in low light. Canon describes it as the world's first lens-shutter 35 mm autofocus camera at the time (Canon, n.d.-b).
- Sonar systems struggle with glass, water, and subjects that are bright or far away. Active systems work best on still subjects at short range.
- Passive AF analyses the light that comes through the lens. It uses either phase detection or contrast detection.
- Phase detection compares two views of the subject taken from opposite sides of the lens. The shift between them tells the camera how far and in which direction to move the focus, so it is fast.
- Contrast detection reads the image sensor and moves the focus until the contrast is highest. It cannot know the direction in advance, so it hunts, and it is slower, mainly with moving subjects.
- Hybrid systems use both. In Canon's Dual Pixel CMOS AF every pixel has two photodiodes, so every pixel can take part in phase detection and also record the image (Canon Singapore, 2022).
- An AF-assist lamp only lights the subject so that passive AF can find contrast in the dark. It is not an active AF system.
- Passive AF needs detail. A smooth surface or a flat colour gives the system little contrast to work with.
| Active AF | Passive AF | |
|---|---|---|
| How it measures | Sends sonar or infrared and reads the reflection | Analyses the light through the lens |
| Examples | Early cameras such as the Polaroid sonar camera and the Canon AF35M | Phase detection, contrast detection, hybrid |
| In the dark | Works at short distance | Needs light and contrast |
| Moving subjects | Poor | Good with phase detection |
Table 2. Active and passive autofocus.
Cham tipIf the camera hunts, aim at an edge with contrast, then recompose.
Cham taskTry to autofocus on a plain wall, then on a book spine. Note which one the camera finds first.
Check yourself: Why does autofocus hunt on a plain white wall?
There is no contrast or detail for the system to measure. Aim at an edge or add light.
What are the focus modes?
Short answer. Cameras offer three ways to focus: once, continuously, or by hand. The names differ from brand to brand, but the ideas are the same.
- Single (one-shot) AF focuses when you press the shutter button halfway, then holds focus so you can recompose. It suits still subjects. On Canon the AF point turns green when focus is found (Canon, n.d.-a).
- Continuous (servo) AF keeps refocusing while you hold the shutter button halfway. It suits moving subjects.
- Focus priority means the shutter fires only when the camera has focus. Release priority means it fires every time you press, even if focus is not confirmed. Nikon sets this separately for AF-C (Nikon, n.d.).
- Automatic AF lets the camera switch between single and continuous depending on whether the subject moves. On Sony it needs a lens that supports phase detection AF (Sony, n.d.).
- Sony also has DMF (Direct Manual Focus), which autofocuses first and then lets you fine-tune by hand. It is useful for macro (Sony, n.d.).
- Manual focus is best when the camera cannot find the intended subject, for example an animal behind a wire fence, where autofocus would lock onto the wire.
- Fujifilm uses S and C for single and continuous AF, and MF for manual focus (Fujifilm, n.d.).
| Idea | Canon | Nikon | Sony | Fujifilm |
|---|---|---|---|---|
| Single, still subject | One-Shot AF | Single-servo AF (AF-S) | Single-shot AF | S |
| Continuous, moving subject | Servo AF (AI Servo AF on older models) | Continuous-servo AF (AF-C) | Continuous AF | C |
| Camera chooses | AI Focus AF (older models) | AF-A | Automatic AF | None |
| By hand | MF | MF | Manual Focus, DMF | MF |
Table 3. Focus mode names by brand. Canon, Sony and Fujifilm follow their manuals. Nikon's names follow its manuals (Canon, n.d.-a; Nikon, n.d.; Sony, n.d.; Fujifilm, n.d.).
Cham tipMatch the mode to the subject: still, single; moving, continuous.
Cham taskPhotograph a person walking towards you, once in single AF and once in continuous AF. Count how many pictures are sharp.
Check yourself: Which mode would you use for a bird in flight?
Continuous AF (AF-C or Servo), because the subject keeps moving.
What are focus points and AF area modes?
Short answer. Focus points are the small squares you see in the viewfinder or on the screen. They show where the camera measures focus, and mirrorless cameras can have hundreds of them across most of the frame.
- Old SLRs offered only a few points, mostly near the centre. Most DSLRs have about 10 to 60, while mirrorless cameras cover a wider area.
- The Sony a6000 has 179 phase-detection points and 25 contrast-detection points. The Sony a7 II has 117 phase-detection points and 25 contrast-detection points (DPReview, n.d.; Photography Life, n.d.).
- A line (vertical) sensor detects detail in one direction. A cross-type sensor detects it in two directions, so it is more accurate. Makers often state how many of their points are cross-type.
- AF point coverage tells how far the points reach towards the edges of the frame. Wide coverage helps you keep tracking a subject that moves to the edge.
- Single point uses one point and suits still subjects such as landscapes and products. A zone or group mode uses a small cluster, which helps with birds and non-team sports. A wide or auto mode lets the camera choose, often a face or the nearest subject. Tracking modes follow a moving subject.
- Fujifilm calls its modes Single Point, Zone and Wide/Tracking, with an All setting that cycles through them (Fujifilm, n.d.).
- Eye AF finds the eyes of a person or an animal and follows them.
| Job | Nikon | Canon | Sony | Fujifilm |
|---|---|---|---|---|
| One point | Single-point AF | Manual AF point | Flexible spot | Single Point |
| One point with helpers while the subject moves | Dynamic-area AF | AF point expansion | Lock-on: flexible spot | Wide/Tracking |
| A small group of points | Group-area AF | Zone AF | Zone | Zone |
| The whole frame | Auto-area AF | Auto AF area | Wide | Wide/Tracking |
| Eyes | Eye-detection AF | Eye AF | Eye AF | See manual |
Table 4. AF area mode names by brand. Names follow each maker's manual. Menus change from model to model, so check your own camera (Fujifilm, n.d.).
Cham tipMove the focus point onto the subject, then half-press. Do not focus on the middle and hope.
Cham taskOpen your camera menu and write down the name of every AF area mode it has.
Check yourself: Which area mode suits a bird that flies unpredictably?
A zone or group mode, because a small cluster of points is easier to keep on the bird than a single point.
How do aperture and light affect autofocus?
Short answer. The camera focuses with the lens opened to its widest aperture and closes it only when the picture is taken. So a lens with a wide maximum aperture helps autofocus, and a dim, low-contrast scene makes it harder.
- The camera keeps the aperture wide open while you compose and focus. It closes to the f-number you chose only when you fully press the shutter button, then opens again.
- For example, if you set f/8 on a 24-70 mm f/2.8 lens, the camera focuses at f/2.8 until the shutter fires.
- On a variable-aperture lens such as a 70-300 mm f/4-5.6, the widest aperture changes with the zoom: f/4 at 70 mm and f/5.6 at 300 mm.
- Some focus points stop working if the widest aperture is smaller than the camera needs. The cut-off is usually between f/5.6 and f/8, so a lens with a tele-extender can lose points. Then use the centre point, which is the most sensitive.
- Canon says Dual Pixel CMOS AF makes use of the full light of fast lenses and is not held back by the f-number limits of older DSLR phase-detection sensors (Canon Singapore, 2022).
- Wide apertures of f/4 and wider help autofocus because more light reaches the AF system. Small apertures such as f/8 and above make it harder.
- Low light and low contrast make autofocus harder. Bright, high-contrast subjects focus more easily than dark or plain ones.
Cham tipIf AF fails with a tele-extender, switch to the centre point.
Cham taskCheck your lens and write down its widest aperture at the shortest and the longest zoom setting.
Check yourself: You set f/16. At what aperture does the camera focus?
At the widest aperture of the lens. It stops down to f/16 only when the picture is taken.
How do I focus by hand and lock focus?
Short answer. Manual focus, back-button focus and focus lock all separate focusing from the shutter button. Tools such as focus peaking, a follow focus and focus stacking help you control exactly where the sharp plane lies.
- Back-button focus moves autofocus from the shutter button to a button on the back of the camera, usually AF-ON. You focus with your thumb and fire the shutter separately, so the camera does not refocus every time you press.
- AF-ON starts focusing without using the shutter button. In single AF, holding it keeps the focus fixed. In continuous AF, the camera keeps refocusing while you hold it.
- To set it up, open the custom controls in the menu. Make the shutter button start metering only, and make the AF-ON button start metering and autofocus. The names and menus differ between models, so check your manual.
- The AE-L/AF-L button locks exposure and focus. Exposure lock fixes the shutter speed, aperture and ISO. You can also set it to lock focus only.
- Focus peaking puts a coloured overlay on the sharpest parts of the live image to help manual focusing. It looks for strong edge contrast.
- A follow focus is a set of gears and a knob on the lens that lets the focus puller turn the focus ring smoothly and repeat the same pull. The focus puller is usually the first assistant camera operator.
- Focus stacking merges several pictures taken at different focus distances into one picture with more depth of field than any single frame.
- Cinema work leans on manual focus and a follow focus for focus pulls and rack focus. RED's KOMODO has an autofocus setting, marked beta in its guide, and it works only with lenses that support EF-type autofocus (RED Digital Cinema, n.d.).
| Tool | What it does | Use it when |
|---|---|---|
| Back-button focus | Separates focusing from the shutter button | You track moving subjects or recompose often |
| AF lock | Holds the focus while you recompose | You focus first, then change the framing |
| Focus peaking | Shows a coloured overlay on sharp edges | You focus by hand in live view |
| Follow focus | Gives smooth, repeatable focus pulls | You shoot film or video |
| Focus stacking | Merges frames to extend depth of field | You shoot macro or products |
Table 5. Focus aids.
Cham tipUse focus peaking to find the plane, then check the key detail with magnification.
Cham taskTurn on focus peaking and focus by hand on a book, then on a plant. Compare how easy each is.
Check yourself: Why use back-button focus?
It separates focusing from firing the shutter, so the camera does not refocus every time you press the shutter button.
How does focus pulling work?
Short answer. Focus pulling means turning the focus by hand during a shot, so the sharp plane follows the actor or moves from one subject to another. The focus puller does it, usually with a follow focus, and works from marks set before the take.
- A focus pull changes the focus during a shot. It keeps a moving subject sharp, or it moves the sharp plane from one subject to another. When it is done on purpose to change what the audience looks at, it is called a rack focus.
- The focus puller is usually the first assistant camera operator. The camera operator watches the framing and the movement. The focus puller watches the focus and turns the focus ring. They work as a pair.
- A follow focus makes the pull smooth. It clamps on rails in front of the camera. A gear on its arm meshes with a gear ring on the lens, and a knob turns it. Beside the knob is a white disc on which the puller writes marks.
- Before the take, the puller measures the distance from the sensor plane mark on the camera body to each position of the actor. Each distance gets a mark on the disc. During the take, the puller hits the marks at the right moment.
- The shallower the depth of field, the smaller the margin for error. On a close-up at a wide stop it can be a few centimetres. See the depth of field guide.
- A pull is rehearsed. The puller learns the actor's moves, watches the monitor, and keeps the eyes between the near and far limits. A slow pull feels gentle. A fast pull feels sudden.
- Autofocus is rarely used for planned pulls, because the camera cannot know which subject the director wants next.
| Term | What it means | Example |
|---|---|---|
| Focus pull | Changing the focus by hand during a shot | An actor walks towards the camera and the eyes stay sharp |
| Rack focus | A pull that moves the sharp plane from one subject to another on purpose | From a ring on the table to the face behind it |
| Follow focus | The knob and gears that turn the focus ring of the lens | Clamped on rails in front of the camera |
| Focus puller | The crew member who makes the pull, usually the first assistant camera operator | Stands beside the camera and watches the actor |
| Marks | Pencil lines on the white disc of the follow focus, one for each distance | One mark for the start position and one for the end |
Table 6. Focus pulling terms.
Cham tipMark the start and end distances on the disc before the take, then rehearse once with the actor.
Cham taskPut two bottles 1 m and 3 m from the camera. Pull focus from one to the other in two seconds, ten times. Count how many times the second bottle is sharp at the end.
Check yourself: What is the difference between a focus pull and a rack focus?
A focus pull is any change of focus by hand during a shot. A rack focus is a pull that moves the sharp plane from one subject to another on purpose.
Where should I focus: hyperfocal distance and the one-third rule?
Short answer. The hyperfocal distance is the closest focus distance at which objects at infinity still look acceptably sharp. When you focus there, everything from half that distance to infinity is sharp.
- Hyperfocal distance is the focal length squared divided by the f-number times the circle of confusion, all in the same units.
- The circle of confusion is the largest blur circle that still looks like a point. For 35 mm work, values between 0.025 mm and 0.035 mm are often chosen (Atkins, n.d.).
- Example: a 24 mm lens at f/8 with a circle of confusion of 0.03 mm gives 24 x 24 / (8 x 0.03) = 2400 mm. Focus at about 2.4 m and everything from about 1.2 m to infinity should look acceptably sharp.
- The hyperfocal distance grows with the focal length and shrinks as the f-number rises. In the field, use an app or a chart instead of calculating.
- The 1/3 - 2/3 rule says that one third of the depth of field lies in front of the focus point and two thirds behind it. It is only a rough guide, because the ratio changes with the lens, the aperture and the distance, and for close-up work the two sides are about equal (Atkins, n.d.).
- With two subjects at different distances, focus about one third of the way from the nearer to the farther one. For subjects at 8 ft and 14 ft, focus at about 10 ft.
Cham tipCheck the sharpness at the near and far edge of the scene in the playback, and zoom in.
Cham taskWork out the hyperfocal distance for your lens at f/8 and at f/16, then test both on a street.
Check yourself: A 24 mm lens at f/8 and c = 0.03 mm: where do you focus, and what is sharp?
About 2.4 m. Everything from about 1.2 m to infinity should look acceptably sharp.
Which focus settings suit each kind of photography?
Short answer. Choose the AF mode by how the subject moves, and the AF area by how large the subject is in the frame. Moving subjects need continuous AF. Still subjects need single AF. Treat every line below as a starting point.
- Birds. Continuous AF, a zone or tracking area, animal eye AF if your camera has it, and back-button focus.
- Animals and pets. Continuous AF with eye AF for animals. Focus on the nearer eye.
- Reptiles. They often stay still, so use single AF with one point on the eye. Behind glass or wire, switch to manual focus.
- Insects and macro. Manual focus with focus peaking, or move the camera instead of the ring. Use focus stacking for more depth.
- Portraits. Single AF with eye AF, or one point on the nearer eye.
- Fashion. Eye AF with continuous AF when the model moves. One point for posed frames.
- Wedding and events. Single AF for posed shots. Continuous AF with a zone for the walk down the aisle.
- Product. Manual focus with magnified live view, or single AF with one point. Use focus stacking to keep the whole product sharp.
- Automotive. Continuous AF with a zone for rolling shots and panning. Back-button focus keeps the thumb in charge.
- Photojournalism. Continuous AF with a zone or wide area and back-button focus, so you can fire the moment it happens.
- Sports and action. Continuous AF, a zone or tracking area, and back-button focus.
- Landscape. Single AF with one point, or manual focus set to the hyperfocal distance.
- Street and documentary. Set the hyperfocal distance and shoot, or use continuous AF with a zone.
- Night and astro. Manual focus with magnified live view on a bright star or light. The AF-assist lamp reaches only a few metres.
- Cinema. Manual focus with a follow focus. Continuous AF only for run and gun.
Questions beginners ask
What is focus?
Focus is the point where light from the subject meets on the sensor, so that part of the picture is sharp. The camera moves lens elements to set it.
What is the difference between active and passive autofocus?
Active autofocus sends out its own sonar or infrared signal and reads the reflection. Passive autofocus only analyses the light that comes through the lens, with phase detection or contrast detection.
Which focus mode should I use for moving subjects?
Use continuous AF, called AF-C on Nikon and Sony, Servo AF on Canon, and C on Fujifilm. It keeps refocusing while you hold the shutter button halfway.
What is back-button focus?
It moves autofocus from the shutter button to a button on the back, usually AF-ON, so you focus with your thumb and fire the shutter separately.
References
- Atkins, B. (n.d.) Depth of Field in Depth! Bob Atkins Photography. bobatkins.com/photography/technical/depth_of_field.html
- Canon Singapore (2022, updated 2026) ‘Canon Technology Explainer: What is Dual Pixel CMOS AF?’, Snapshot, 16 December. snapshot.asia.canon/en/article/canon-technology-explainer-what-is-dual-pixel-cmos-af
- Canon. (n.d.-a) AF Operation. Canon EOS R6 Advanced User Guide. cam.start.canon/en/C004/manual/html/UG-04_AF-Drive_0040.html
- Canon Inc. (n.d.-b) Film Cameras: AF35M. Canon Camera Museum. global.canon/en/c-museum/product/film102.html
- DPReview. (n.d.) Sony Alpha a6000 Review, autofocus page. www.dpreview.com/reviews/sony-alpha-a6000/4
- Fujifilm. (n.d.) AF/MF SETTING (Still Photography). X-T4 Owner’s Manual. fujifilm-dsc.com/en/manual/x-t4/menu_shooting/af_mf_setting/index.html
- Nikon. (n.d.) a1: AF-C Priority Selection. D850 Online Manual. onlinemanual.nikonimglib.com/d850/en/18_menu_guide_05_a01.html
- Photography Life. (n.d.) Sony a7 II Review: Autofocus / Manual Focus Performance and Metering. photographylife.com/reviews/sony-a7-ii/4
- RED Digital Cinema. (n.d.) Autofocus (BETA). KOMODO Operation Guide, v1.3. docs.red.com, KOMODO Operation Guide, Autofocus (BETA)
- Sony. (n.d.) Focus Mode. ILCE-6400 Help Guide. helpguide.sony.net/ilc/2450/v1/en/contents/0405C_focus_mode.html
How to cite this guide. Alex, A., & Joseph, A. (2026). Focus: A guide for photographers and cinematographers. Creative Hut Academy. https://creativehut.org/library/what-is-focus/
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