Depth of Field Calculator

Sensor format:

Focal length: {{ focalReadout }}

Use the physical focal length printed on the lens.

Aperture: {{ apertureReadout }}

Enter the working f-number; the slider provides quick tuning.

Focus distance:

Use the lens-to-subject focus distance; changing units preserves the physical distance.

Subject distance unit

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Blur tolerance:

Standard uses the sensor baseline. Relative or custom blur tolerances refine the same focus calculation.

Circle of confusion:

Set a sensor-plane blur diameter from 0.001 to 0.200 mm.

Background distance:

Optional plane beyond focus. An invalid background affects this check only.

Background distance unit

Subject height in frame:

Optional framing coverage: zero omits the height check and leaves focus limits unchanged.

Subject height unit

Frame orientation:

Swaps the framing dimensions and leaves depth of field unchanged.

Forward/back movement:

The neutral 0 default omits the motion check.

Subject motion allowance unit

Compare a second setup:

Compare another focal length, aperture or focus distance using the same sensor and blur tolerance.

Setting B focal length:

Physical focal length for Setting B, using the same sensor and blur tolerance.

Setting B aperture:

Working f-number for Setting B; the primary setup remains unchanged.

Setting B subject distance:

Focus distance for Setting B. Invalid values affect this comparison only.

Setting B subject distance unit

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Turn on Compare a second setup in Advanced to review another lens, aperture, or focus distance.

This is a conceptual illustration of relative background blur; use the numeric blur-circle result in the focus brief. It does not model aperture-blade shape, lens aberrations, foreground blur, or the artistic character of bokeh.

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Focus is exact at one distance, but photographs are judged over a range that looks acceptably sharp. Depth of field is the distance from the nearest acceptable point to the farthest one. The transition is gradual rather than a physical boundary, so every calculated near or far limit depends on a chosen tolerance for blur.

That tolerance is called the circle of confusion. It represents the largest blur circle on the sensor that will still look like a point in the intended output. Sensor format supplies a conventional starting value, but print size, viewing distance, display resolution, cropping, eyesight, and the amount of fine detail can justify a looser or stricter value.

Camera settings and their practical depth of field effects
Change	Typical effect at the same camera position	Tradeoff
Use a higher f-number	Near limit moves closer and far limit moves farther	Less light and eventually more diffraction softening
Focus farther away	Depth of field generally becomes deeper	Subject magnification and composition change
Use a longer focal length	Depth of field becomes shallower at the same distance	Field of view narrows
Use a stricter blur tolerance	Acceptable range becomes narrower	Better suited to large output or close inspection

Focal length comparisons are easy to misread. Changing from 50 mm to 85 mm without moving changes both magnification and depth of field. Moving the camera to preserve the same framing changes focus distance as well, and the total depth of field may become much closer than a same-position comparison suggests.

Depth of field does not describe every visual quality. Background separation also depends on the background distance and the diameter of its defocused blur circles. Motion can carry a subject outside the calculated near or far allowance. Lens aberrations, focus breathing, diffraction, bokeh shape, autofocus error, and real focal length are separate limits that a thin-lens estimate cannot predict.

How to Use This Tool:

Describe the intended output and physical camera setup before comparing apertures or lenses.

Choose the Sensor format. The standard blur tolerance is ready to use; refine it in Advanced when the intended output calls for a different circle of confusion.
Enter Focal length, Aperture, and Subject distance. Subject distance is measured from the lens plane in this model and must be greater than the focal length.
Open Advanced for scene checks. Background distance, subject height, orientation, forward/back movement and comparison are optional. Invalid scene details stay unavailable without erasing valid focus limits.
Read the near and far limits before looking at total depth. Compare front and rear allowance with the subject's actual movement or physical thickness.
Turn on Compare a second setup when testing another focal length, aperture, or camera position. Keep framing assumptions explicit so the comparison answers the intended question.

Interpreting Results:

Near limit and Far limit mark where the selected circle-of-confusion tolerance is reached. They do not mean everything inside is equally sharp. Detail begins losing sharpness immediately on either side of the focus distance.

An infinite far limit means the focus distance is at or beyond the calculated hyperfocal distance. It does not mean foreground objects are sharp.
Background blur estimates the blur-circle diameter for the entered background plane. The ratio compares it with the acceptable circle of confusion; it does not rate bokeh quality.
Movement within DOF requires both the front and rear depth to meet the entered allowance, unless the far limit is infinite.
Subject coverage is a framing estimate from subject height and calculated field height. Values above 100% mean the entered subject height exceeds the frame height.

Technical Details:

The model uses classical thin-lens depth-of-field equations. Focal length, circle of confusion, subject distance, near and far limits, and hyperfocal distance are converted to millimetres before calculation. Aperture is the dimensionless f-number.

Formula Core:

Hyperfocal distance H is set by focal length f, f-number N, and circle of confusion c.

H = \frac{f^{2}}{N c} + f

For subject distance s, the near limit always remains finite. The far limit becomes infinite when s is at least H.

D_{n} = \frac{s (H - f)}{H + s - 2 f}, D_{f} = \frac{s (H - f)}{H - s} when s < H

Front depth is s − D_n. Rear depth is D_f − s when the far limit is finite, and total depth is D_f − D_n. Numeric results retain up to 12 significant digits before display formatting. Small focus spans use appropriate smaller metric units or inches and remain nonzero in the result.

Sharpness targets:

Sensor circles of confusion and sharpness multipliers
Sensor format	Standard c	Profile adjustment
Full frame, 36 × 24 mm	0.030 mm	Relative tolerances: 1.35×, standard 1×, 0.7× or 0.5×. These are explicit planning multipliers, not calibrated print-size requirements.
APS-C, 23.6 × 15.7 mm	0.020 mm
Canon APS-C, 22.3 × 14.9 mm	0.019 mm
Micro Four Thirds, 17.3 × 13 mm	0.015 mm
1-inch type, 13.2 × 8.8 mm	0.011 mm
Medium format, 44 × 33 mm	0.040 mm

A smaller c demands a smaller blur circle and therefore narrows the acceptable range. A custom value must be from 0.001 to 0.200 mm.

Background blur and framing:

The background-plane estimate first calculates the image distance v for the focused subject and background with the thin-lens relation. It then measures the defocus circle produced by the aperture diameter f/N.

v (x) = \frac{f x}{x - f}, b = | \frac{f}{N} \times \frac{v (x_{b}) - v (s)}{v (x_{b})} |

x_b is background distance and b is the sensor-plane blur diameter. The reported blur ratio is b/c. Framing uses sensor dimensions after orientation is applied:

F_{w} = \frac{s S_{w}}{f}, F_{h} = \frac{s S_{h}}{f}

All 11 aperture points remain in the chart and CSV at every screen width. Chart images identify the lens, focus distance and blur tolerance; CSV includes those same assumptions alongside the raw millimetre results. The aperture ladder recalculates near limit and hyperfocal distance at f/1, 1.4, 2, 2.8, 4, 5.6, 8, 11, 16, 22, and 32 while keeping focal length, subject distance, sensor, and sharpness target fixed.

Accuracy Notes:

The equations describe an ideal thin lens and an acceptability threshold. They are useful for planning, but the captured image remains the final test.

Macro and close-up work may require pupil magnification and lens-specific focus behavior that are not modeled.
Marked focal length, aperture, and focus distance may differ from their effective values.
Diffraction, aberrations, focus shift, camera movement, autofocus error, and subject movement can reduce usable sharpness.
The blur-circle estimate describes size at one background plane, not highlight shape, edge character, or bokeh quality.

Worked Examples:

Full-frame 50 mm setup at f/8

With a standard 0.03 mm circle of confusion and focus at 5 m, the hyperfocal distance is about 10.47 m. The near limit is about 3.39 m and the far limit about 9.53 m, giving roughly 6.14 m of modeled depth. A background at 10 m produces a 0.0316 mm blur circle, only about 1.05 times the acceptable tolerance, so strong background separation should not be assumed.

Wide-angle focus beyond hyperfocal

For 24 mm at f/8 on full frame with focus at 3 m, the hyperfocal distance is 2.424 m. Because the subject distance is beyond that value, the far limit is reported as infinity while the near limit remains about 1.34 m. Objects closer than the near limit are still outside the chosen tolerance.

FAQ:

Why does changing sensor format change depth of field?

In this model, sensor format selects a conventional circle of confusion and sensor dimensions. A fair camera-format comparison must also decide whether focal length, camera position, framing, output size, and sharpness tolerance stay fixed; changing those assumptions can change the conclusion.

References:

Depth of Field Equations, DOFMaster, 2003.
Understanding Depth of Field in Photography, Cambridge in Colour.