Depth of Field and Circle of Confusion
Computes total depth of field in meters between near and far limits from focal length, f-number, subject distance and circle of confusion.
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Depth of field and circle of confusion
The circle of confusion (CoC) is the biggest blur spot your eye still reads as sharp. A common way to pin it down is c = d / 1500, with d being the sensor diagonal. That puts full-frame ≈ 0.030 mm, APS-C ≈ 0.020 mm and Micro Four Thirds ≈ 0.015 mm. Once your subject sits well short of the hyperfocal, depth of field is close to DOF ≈ 2·N·c·(s/f)², where N is the aperture, s the subject distance and f the focal length. Run a 50 mm at f/5.6, 3 m, CoC 0.03 mm through that and you land around 1.2 m of DOF.
Applications
Photographers lean on depth-of-field calculations for portrait, landscape and product shoots, and to match gear to whatever sensor format they want to work with. In macro work it underpins focus stacking, where you take overlapping slices of shallow DOF and merge them into one image that is sharp front to back.
FAQ
Why does a smaller sensor seem to have more DOF? A smaller CoC does ask for a tighter focus tolerance, which would pull the other way. But to keep the same field of view you reach for a shorter focal length, and that effect wins out. The (s/f)² term grows and DOF expands with it.
What CoC should I pick? For prints, the manufacturer default for your sensor (d/1500) does the job. If you are pixel-peeping on a 4K monitor, drop to something stricter like d/3000, which matches what you will actually see.
What is hyperfocal distance? It is the nearest point you can focus on while still keeping the far edge of DOF out at infinity. The formula is H = f² / (N·c) + f, and focusing there keeps everything from H/2 to infinity acceptably sharp.
Related Tools
Depth of Field (DOF) Calculator
Focal length in mm, f-number, subject distance in m and circle of confusion in mm return the total in-focus range in meters, from the hyperfocal formula.
Depth of Field Calculator
Calculate depth of field from aperture, focal length and subject distance. Result in meters: near, far and total distance.
Circle of Confusion by Sensor Size
Pick a sensor format to get the CoC in mm that depth of field and hyperfocal math need: full frame 0.030, APS-C 0.020, MFT 0.015, 1 inch 0.011.
Lens Field of View by Focal and Sensor
Computes horizontal, vertical and diagonal angle of view of a lens from focal length in mm and sensor size in mm.
Circle and Ellipse Area Calculator
Computes circle area from radius and ellipse area from semi-axes a and b using the standard pi formulas.
Second-Leg Flaw Depth (Angle-Beam Ultrasonics)
Computes the true depth of a discontinuity found on the second leg of the beam in angle-beam ultrasonics, d = 2 × t − S × cos(θ), where S is the sound path read on the instrument and θ is the probe refracted angle. After bouncing off the back wall the beam travels back upwards, so depth stops growing with sound path and starts shrinking: depth is now counted from the back wall, not from the scanning surface, which is the classic mistake of applying the first-leg formula out of range. The tool only accepts sound paths whose projection falls between one and two thicknesses, which is exactly the second-leg band — below that the reflector is on the first leg and d = S × cos(θ) applies. Enter the part thickness, the sound path and the refracted angle.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.