Depth of Field Calculator

Depth of field is the zone in front of and behind your subject that still looks acceptably sharp. It depends on four things: focal length, aperture (f-number), focus distance and sensor size. This calculator uses the standard thin-lens formulas to give the near limit, far limit, total depth of field and hyperfocal distance, and draws the sharp zone on a distance scale. The blur preview works like a simple depth of field simulator: it shows how strongly objects at half, double and six times the subject distance are blurred with your settings, so you can compare f/1.8 against f/8 or a 35 mm lens against an 85 mm lens before you shoot.

First the hyperfocal distance is calculated: H = f² ÷ (N × c) + f, where f is the focal length, N the f-number and c the circle of confusion – the largest blur spot that still looks sharp in a normally viewed print. The near limit is s(H − f) ÷ (H + s − 2f) and the far limit is s(H − f) ÷ (H − s) for a subject at distance s; when s reaches H, the far limit becomes infinity. The default circle of confusion is the sensor diagonal divided by 1500 (about 0.029 mm for full frame). You can type your own value if you print large or check images at 100 %, where a smaller value gives stricter results.

To make the depth of field shallower and blur the background more: open the aperture (smaller f-number), move closer to your subject, use a longer focal length, or increase the distance between subject and background. For more depth of field – landscapes, groups, product shots – stop down to f/8 or f/11, step back, or focus at the hyperfocal distance so that everything from half that distance to infinity is acceptably sharp. Very small apertures such as f/22 can soften the whole image through diffraction, so they are not always sharper.

With the same framing and f-number, a smaller sensor gives more depth of field, because you use a shorter lens or stand further away to get the same picture. That is why phone cameras keep almost everything sharp and full-frame cameras blur backgrounds more easily. Pick your sensor in the list – the calculator adjusts the circle of confusion and shows the crop factor. Phone portrait modes create their blur in software, so real phone optics behave like the 'phone' setting here.