Depth of Field Calculator

Depth of Field: DOF ≈ 2·N·c·(s/f)²

Depth of Field (DOF) describes how much of a photo, around the point you focused on, still reads as acceptably sharp. When the subject sits well past the hyperfocal distance, the approximation DOF ≈ 2·N·c·(s/f)² comes in handy. N is the f-number (aperture), c the circle of confusion (about 0.03 mm for full-frame and 0.02 mm for APS-C), s the focus distance and f the focal length in millimeters. Shoot wide open at f/1.4 and the DOF turns shallow, pulling the subject clear of the background. Stop down to f/16 and the whole frame stays sharp. Macro work pushes this to an extreme, with DOF collapsing to millimeters until focus stacking becomes the only way through. Landscape shooters usually focus at the hyperfocal distance, which keeps things sharp from half that distance out to infinity. PhotoPills and DOFMaster crunch these figures for you. Worked example: f=50 mm, N=2.8, s=3 m and c=0.03 mm land at about 0.60 m of DOF.

Applications

Portraits with a soft, creamy background blur (shallow DOF, f/1.4-f/2.8). Landscape work that stays sharp everywhere (deep DOF, f/8-f/16 or hyperfocal focus). Macro and product photography leaning on focus stacking. Cinematography, where focus pulls and rack focus drive the shot. The same math underpins security and surveillance optics, microscopy and astrophotography.

FAQ

Why does sensor size affect DOF? A smaller sensor needs a shorter focal length to match the same framing, and shorter focal lengths give you deeper DOF. That's the reason phones look in focus everywhere, while a full-frame camera can blur the background heavily.

What is the circle of confusion? It's the largest blur spot a viewer at standard distance still takes for a single point. Common industry defaults 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 focus point that still keeps infinity acceptably sharp. Focus there and the DOF stretches as far as possible, holding everything from half that distance to infinity in focus. Landscape photographers reach for this trick all the time.