Sharp focus separates professional images from amateur snapshots. Even perfect exposure and composition mean nothing if your subject appears soft. Modern cameras offer sophisticated autofocus systems, but understanding how they work determines whether they help or hinder your photography.
This guide explains focus systems, autofocus modes, manual focus techniques, and strategies for achieving tack-sharp results in any situation.
Understanding Focus Points
Your camera’s viewfinder displays focus points, small squares or dots indicating where the camera can focus. Entry-level cameras might have 9-11 points, while professional bodies feature 50 or more covering most of the frame.
Cross-type focus points detect contrast in both horizontal and vertical directions, providing more reliable focus than linear points. Most cameras concentrate cross-type points centrally.
Selecting a single focus point gives you control over focus placement. Leaving all points active allows the camera to choose, which often defaults to the nearest subject, not necessarily your intended subject.
Autofocus Modes
Single-Shot AF (AF-S/One-Shot)
Single-shot autofocus locks focus when you half-press the shutter button. Focus remains fixed until you release and refocus. This mode suits stationary subjects where you can compose after focusing.
Continuous AF (AF-C/AI Servo)
Continuous autofocus tracks moving subjects, continuously adjusting focus as distance changes. Essential for sports, wildlife, and any moving subject. The camera predicts movement and pre-focuses for anticipated position.
Automatic Mode Selection
Some cameras offer automatic switching between single and continuous modes based on detected movement. This convenience comes with occasional incorrect decisions. Most experienced photographers prefer deliberate mode selection.
When to Use Manual Focus
Low light challenges autofocus systems that rely on detecting contrast. When your camera hunts without locking focus, manual focus provides reliable results.
Macro photography often requires manual focus due to extremely shallow depth of field. Precise focus placement matters when only millimetres appear sharp.
Shooting through fences, glass, or foliage confuses autofocus systems that may lock onto obstacles rather than your subject. Manual focus bypasses these distractions.
Back-Button Focus
Back-button focus separates focusing from the shutter button, assigning autofocus to a rear button (often AF-ON) while the shutter only fires. This technique provides single-shot behaviour when you press once and continuous behaviour when you hold the button.
Many professional photographers adopt back-button focus for its flexibility. Camera manuals explain the specific configuration for your model.
Common Focus Mistakes
Focus hunting occurs when the camera searches without locking, often in low contrast or low light. Switch to manual focus or find a higher-contrast area to focus on.
Focusing on the wrong subject happens when all focus points are active. Select a single point or small group and place it precisely on your intended subject.
Master focus techniques with hands-on guidance through the Certificate in Photography where tutors provide feedback on your images.
Develop confident focusing skills with professional training at Australian Photography School.
