Depth of field calculator.

Only the plane you focus on is mathematically exact. Points in front of or behind it are projected as small discs. Depth of field (DOF) is the distance between the nearest and farthest planes whose discs remain smaller than the selected circle of confusion, so they appear acceptably sharp at an assumed viewing size.

This simulator calculates those near and far limits, total DOF, hyperfocal distance, field of view, magnification, and the blur-disc diameter at the background. The boundary is a useful convention rather than a sudden transition from sharp to blurry.

For focal length f, f-number N, acceptable circle of confusion c, and focus distance s, the hyperfocal distance is H = f²/(N × c) + f. Set q = N × c × (s − f). The near limit is f² × s / (f² + q); the far limit is f² × s / (f² − q) when s is below H, otherwise infinity.

These limits solve the same blur equation as the renderer, in millimetres. Real lenses can depart from thin-lens geometry at close focus because of focus breathing, pupil magnification, and internal focusing. Read the equations and worked example.

Background blur describes how much an out-of-focus detail spreads. Bokeh describes the character of that blur: whether highlights look smooth, nervous, circular, polygonal, swirled, or clipped near the frame edge.

The calculated background CoC is a physical blur diameter on the sensor. The preview then uses aperture blade count and roundness to illustrate highlight shape. It cannot reproduce a particular lens’s aberrations or cat-eye bokeh, so use the number for comparison and the rendering as an explanation.

After the lens is focused on the subject, light from another distance converges in front of or behind the sensor and reaches the sensor as a disc instead of a point. Increasing the subject-to-background gap generally enlarges that disc until the result approaches a practical limit.

For a portrait, moving the subject away from the wall often changes separation more predictably than buying a faster lens. Try changing only “Background distance” to see the effect while every camera setting stays fixed.

At a small aperture, light diffracts around the edges of the diaphragm blades. Bright point sources can produce rays related to the blade geometry: an even blade count commonly produces the same number of rays, while an odd count produces twice as many because opposite rays do not overlap.

Stopping down also enlarges the Airy diffraction pattern. You gain geometric depth of field, but fine detail can lose contrast. The simulator’s 550 nm Airy-disk value and star graphic explain that trade-off; they are not a full diffraction model for a specific lens or sensor.

To match framing from the same camera position, divide the full-frame focal length by the crop factor. A 50 mm full-frame view is roughly 33 mm on 1.5× APS-C, 31 mm on 1.6× APS-C, or 25 mm on 2× Micro Four Thirds.

To also approximate the same depth of field and entrance-pupil diameter, divide the full-frame f-number by the crop factor: full-frame 50 mm f/2.8 is approximately 33 mm f/1.9 on 1.5× APS-C or 25 mm f/1.4 on 2× Micro Four Thirds. Keep subject distance, aspect ratio, framing, and final viewing conditions matched. Exposure remains governed by the actual f-number—not the “equivalent” one.

If camera position and aperture stay fixed, a longer focal length magnifies the subject and usually narrows DOF. If you step backward to keep the subject the same size, the DOF difference becomes much smaller at ordinary portrait distances, although perspective and the apparent size of the background change.

Turn on “Keep subject size” in the advanced panel to distinguish a focal-length change from a framing change. Pin setup A before adjusting setup B for a direct comparison.

Hyperfocal distance is the nearest focus distance whose far DOF limit reaches infinity under the chosen CoC standard. Focusing there makes objects from roughly half that distance to infinity acceptably sharp by that standard.

It is helpful for landscapes and zone focusing, but it is not a promise of equal sharpness everywhere. If the distant subject matters most, focus farther than the calculated hyperfocal point or verify at the intended output size.

Choose your actual camera and lens, enter the camera-to-subject distance, then enter the camera-to-background distance. Change one setting at a time. Read “Sharp from” and “Sharp to” for the acceptable focus zone, and use Background CoC to compare blur quantitatively.

Depth model applies separate calculations to illustrated distance planes. Photo backdrop is useful for composition, but its original softness is baked into the image and cannot become sharp when you stop down. Always confirm an important shot with magnified live view or a test frame.