Focus is the adjustment of the lens to make the subject appear sharp. When light rays from the subject converge precisely on the sensor, the image is in focus. When they converge in front of or behind the sensor, the image is blurry. Focus can be adjusted manually, by turning a ring on the lens, or automatically, by the camera's autofocus system. Both have their place. Autofocus is fast and accurate in most situations. Manual focus is precise and reliable when autofocus struggles, such as in low light or when shooting through glass.

Focus is not just a technical setting. It is a creative choice. Deciding what to focus on decides what the viewer looks at first. In a portrait, the eyes are usually the focus point. In a landscape, the hyperfocal distance keeps everything from a certain point to infinity acceptably sharp. In macro photography, focus is critical and depth of field is razor-thin. Focus peaking, focus magnification, and focus assist are tools that help manual focus users. Focus is also a verb. To focus is to direct attention, and that is what the photographer does with the lens.

Focus techniques

• Autofocus. Camera adjusts the lens automatically.
• Manual focus. Photographer adjusts the lens by hand.
• Back-button focus. Separates focus from the shutter button.
• Hyperfocal distance. Focus point that maximizes depth of field.

Focus is not the same as sharpness. A lens can be sharp but out of focus. A lens can be in focus but soft. Both matter, but they are different things.