Focus and Recompose

Focus and recompose is a technique for sharp focus on a subject that sits away from the focus point. The photographer aims the active focus point, usually the center one, at the subject, half-presses the shutter button to lock focus, and then moves the camera to the final framing while keeping the button half-pressed. The shutter is pressed fully once the composition is right. It is one of the oldest focusing habits in photography and still common with rangefinders and compact cameras.

A lens focuses on a flat plane at a fixed distance, square to the direction the camera points. When the camera pivots after locking focus, the plane pivots with it, and the subject ends up slightly in front of that plane. The sharpest zone lands behind the subject. The shift is tiny at small apertures and normal distances, but at f/1.4, close range, and a large swing it can move an eye out of the sharp zone and the photo looks back-focused.

No. Continuous autofocus (AF-C) keeps measuring and refocusing for as long as the shutter button is half-pressed, so the moment the camera moves it refocuses on whatever now sits under the point, usually the background. Focus and recompose needs single autofocus (AF-S), which locks the distance once and holds it until the shutter fires or the button is released. Back-button focus with the button released works in either mode.

Moving the point is more accurate, because the camera never turns after focusing, so it is the safer choice for portraits at wide apertures and for anything close. Focus and recompose is faster when the center point locks quickly and the framing changes every shot, as in street photography. Many photographers use both: a moved point for a seated portrait, the center point and a recompose for a quick grab shot.

There is no exact number, because the error also depends on distance and on how far the camera swings. As a rule, from f/4 with a subject more than two meters away the shift stays well inside the depth of field. At f/2 and wider with a subject under 1.5 meters, moving the subject from the center to the edge of the frame can produce visible back focus. Stop down, move the focus point, or keep the subject nearer the center.

Back-button focus moves autofocus from the shutter button to a button on the back of the camera. The photographer presses it once to focus on the subject, lets go, and the focus stays locked for as long as needed. The shutter button then only takes the picture, so there is no need to hold a half-press while recomposing, and the camera cannot refocus by accident when the shutter is pressed. Several frames can be taken from one lock.

Yes, and on a rangefinder it is the normal way to focus. The rangefinder patch sits in the center of the viewfinder, so the photographer lines up the subject in the patch, turns the focus ring until the double image merges, and then reframes. Manual focus SLRs with a split prism in the center of the screen work the same way. The geometry is identical, so the same limits apply at wide apertures and close distances.

It can. On many cameras the half-press that locks focus also locks the exposure reading, so the final frame is exposed for whatever was under the center point at the moment of the lock. That is useful when the subject is darker or brighter than the scene, and a problem when it is not. Other cameras keep metering until the shutter fires. The custom menu usually controls this, and a separate AE-L button or manual mode keeps focus and exposure independent.

On most cameras the center point is the fastest and most sensitive one. On DSLRs it is often the only cross-type point that works with slow lenses and in dim light. On mirrorless cameras the gap is smaller, but the center is still the easiest point to find without looking, and it is where a rangefinder patch, a split prism, and a compact camera's single area all live. Starting from the center also makes the habit the same on every camera.

Yes. Tapping the screen sets focus and exposure on that spot, and on most phones a long press locks both, shown as an AE/AF lock label. The phone can then be moved to the final framing and the lock holds. Because phone lenses have small sensors and deep depth of field, the focus shift from recomposing is rarely visible, though the exposure lock can matter when the final frame contains a bright sky or window.