The short version
- AF-S (One Shot) locks focus once: best for still subjects like portraits and landscapes.
- AF-C (AI Servo) tracks continuously: best for anything moving, like kids, pets and sports.
- Single-point area gives you precise control; wide/auto area lets the camera choose.
- Back-button focus separates focusing from the shutter button for faster, more deliberate shooting.
- If the camera keeps focusing on the background, your focus area is too wide or the point is in the wrong place.
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How autofocus actually works
Modern cameras focus in two main ways. Contrast detection analyzes the image on the sensor and hunts for maximum contrast, which is accurate but slow. Phase detection uses dedicated sensors (or pixels on the sensor) to measure exactly how far out of focus the lens is and drive it straight there, which is fast. Most mirrorless cameras now use on-sensor phase detection, which is why their autofocus feels instant.
What matters to you: give the system contrast to bite on. It struggles on blank walls, clear skies and in near darkness. Aim a focus point at an edge, an eye or a textured surface and it locks quickly.
AF-S vs AF-C: the only setting that matters most
| Mode | Canon name | What it does | Use for |
|---|---|---|---|
| AF-S | One Shot | Locks focus when you half-press, then holds it | Portraits, landscapes, still life |
| AF-C | AI Servo | Keeps refocusing as the subject moves | Sports, kids, pets, wildlife |
| AF-A | AI Focus | Camera guesses between the two | Beginners, unpredictable scenes |
The classic beginner error is shooting running kids in AF-S: you lock focus, the kid moves two steps, and every shot is soft. If anything in your frame might move, use AF-C. Pair it with a fast shutter speed and the camera does the hard part.
Many cameras also offer eye detection now. Turn it on for people and animals; it finds eyes automatically and is the single biggest sharpness upgrade for portrait shooters.
Focus points, zones and wide area
The focus area decides how much of the frame the camera may use:
- Single point: one small square you move with the joystick or touchscreen. Maximum control, best for portraits (put it on the nearest eye) and landscapes.
- Zone: a cluster of points. A middle ground for subjects that move a little, like a toddler in one spot.
- Wide / auto: the camera picks what it thinks is the subject. Fast and easy, but it loves high-contrast backgrounds and will happily focus on the fence behind your kid.
Start with single point for still subjects and zone for moving ones. Graduate to wide only once you trust the camera's subject detection, and check the first few shots zoomed in.
Why your shots are misfocused
- Focus point on the background. The most common cause of "my camera focused behind my subject." Move the point onto the subject, or shrink the focus area.
- Wrong mode for the subject. AF-S on moving subjects guarantees misses. When in doubt, AF-C.
- Focus and recompose at f/1.4. Locking on the eye then rotating the camera shifts the focus plane. At wide apertures the eye goes soft. Move the focus point instead; read our aperture guide for why depth of field is so thin here.
- Shooting through fences or branches. The camera grabs the nearest contrast. Switch to single point and place it precisely on the subject.
Practical autofocus tips
- For portraits, always focus on the nearest eye. Everything else is secondary.
- In low light, find the contrastiest edge near your subject and focus there, then recompose.
- Turn on eye detection for people and animals if your camera has it.
- For sports, use AF-C with a zone area and a shutter speed of at least 1/1000. See our shutter speed guide for the full chart.
- Zoom into your shots on the camera screen to check focus. The thumbnail lies.
Get the printable camera settings cheat sheet
Two pages for your camera bag: starter settings for portraits, landscapes, sports and night shots, the handheld shutter speed rule, and the five settings rules worth memorizing.
Frequently asked questions
Why is my camera focusing on the background instead of my subject?
Your focus area is probably set to wide or auto, so the camera picked the highest-contrast thing, which is often the background. Switch to single-point or zone area and place it on your subject.
Why are my photos blurry even though autofocus is on?
The usual suspects: AF-S mode on a moving subject, a shutter speed too slow for the motion, or the focus point sitting on the wrong thing. Check focus mode first, then shutter speed.
What is back-button focus and should I use it?
It moves focusing from the shutter half-press to a thumb button, so focusing and taking the picture become separate actions. It is worth learning if you shoot both still and moving subjects and hate digging through menus to switch modes.
Should I use AF-S or AF-C for kids and pets?
AF-C, always. Kids and pets never hold still, and AF-S locks focus once and stops tracking. Pair AF-C with a zone focus area.
Why does autofocus hunt back and forth in low light?
The system needs contrast to lock onto, and dark scenes have little of it. Aim at the brightest edge near your subject, use your camera's focus assist light, or switch to manual focus with magnification.
How many focus points do I actually need?
Fewer than marketing suggests. One well-placed single point beats hundreds of auto-selected ones for most shooting. Dense point coverage matters most for tracking fast action across the frame.