Depth of Field Calculator

Depth of field comes from thin-lens optics: only objects at the exact focused distance form a perfectly sharp point on the sensor, but points somewhat nearer or farther still land within an acceptably small blur spot (the circle of confusion) rather than a visibly soft one. The hyperfocal distance H — the focus distance beyond which everything out to infinity stays acceptably sharp — is H = f²/(N·c) + f, where f is focal length, N is the f-number, and c is the circle of confusion.

Once H is known, the near and far limits of acceptable sharpness for a lens focused at subject distance s follow from the same thin-lens defocus relationship: near limit = s(H − f) ÷ (H + s − 2f), and far limit = s(H − f) ÷ (H − s). The far-limit formula's denominator reaches zero exactly when s equals H, which is why focusing at the hyperfocal distance sends the far limit to infinity — and it also means the near limit at that exact focus distance always comes out to precisely H ÷ 2.

Focal length and circle of confusion are entered directly in millimeters regardless of the unit toggle, since photographers worldwide specify both that way by convention; only subject distance — the one field you're likely to think of in meters or feet depending on where you are — switches with the toggle.