Profundidade de Campo (DOF)

Depth of Field: DOF ≈ 2·N·c·(s/f)²

Depth of Field (DOF) is how much of the scene, in front of and behind whatever you focused on, still looks sharp enough. Once your subject sits well past the hyperfocal distance, you can lean on the approximation DOF ≈ 2·N·c·(s/f)². Here N is the f-number (aperture), c the circle of confusion (around 0.03 mm for full-frame and 0.02 mm for APS-C), s the focus distance and f the focal length. Open the lens wide, say f/1.4, and the DOF goes thin enough to lift the subject off its surroundings. Stop down to f/16 and almost everything snaps into focus. Macro photography is a different world: DOF can drop to a couple of millimeters, which is why focus stacking exists. Landscape shooters tend to focus at the hyperfocal distance to squeeze out the most apparent sharpness. PhotoPills and DOFMaster work these numbers out for you. As an example, f=50 mm, N=2.8, s=3 m and c=0.03 mm give roughly 0.60 m of DOF.

Applications

Portraits where the background melts into a creamy blur (shallow DOF, f/1.4-f/2.8). Landscapes that stay sharp front to back (deep DOF, f/8-f/16 or hyperfocal focus). Macro and product shots built up with focus stacking. Cinematography, where focus pulls and rack focus are part of the storytelling. It also shows up in surveillance optics, microscopy and astrophotography.

FAQ

Why does sensor size affect DOF? To get the same framing on a smaller sensor you need a shorter focal length, and shorter focal lengths deepen the DOF. It explains why a phone looks like everything is in focus while a full-frame camera can wash the background out completely.

What is the circle of confusion? It's the biggest blur spot a viewer at normal distance still reads as a single point. The usual industry figures are 0.03 mm for full-frame, 0.02 mm for APS-C and 0.015 mm for Micro Four Thirds.

What is hyperfocal distance? It's the nearest point you can focus on while infinity still holds acceptable sharpness. Set focus there and the DOF runs as far as it can, with everything from half that distance out to infinity staying sharp.