Circle of Confusion (CoC) Calculator

Circle of confusion (CoC) is the largest blur spot on a camera sensor that still appears sharp to the human eye in a final print or display. The CoC value for a given camera sensor feeds depth of field calculations, hyperfocal tables, and acceptable sharpness thresholds, and it shapes decisions about aperture selection, focusing technique, and print size limitations.

• Camera and sensor presets cover full frame, APS-C (Nikon/Sony and Canon), APS-H, Micro Four Thirds, medium format, one-inch sensors, smartphones, and large format film; a custom sensor width and height in millimeters computes the diagonal automatically for anything else.
• Two calculation methods are available. The Zeiss formula divides the sensor diagonal by a standard divisor. The custom visual acuity method computes CoC from print size, viewing distance, and the resolving power of the human eye.
• The Zeiss method's divisor is 1500 for the traditional standard, 1730 for stricter digital sharpness criteria, or 1000 for a more lenient threshold, with custom divisors also accepted.
• The custom method takes viewing distance, print width, print height in millimeters, and visual acuity in line pairs per millimeter. The standard 5 lp/mm at 250 mm corresponds to 20/20 vision.
• Results display in millimeters, microns, and inches, with a step-by-step derivation available showing the full formula with the entered values substituted in.
• Input fields accept decimals (0.75), fractions (3/4), and mixed numbers (5 1/16), and settings are saved automatically and restored on return.

The circle of confusion is a foundational optical parameter used across photography, cinematography, optical engineering, and print production. Knowing the correct CoC for a specific camera and output medium keeps depth of field calculations, hyperfocal tables, and sharpness evaluations accurate rather than based on generic assumptions.

• Landscape Photography: Calculate the precise CoC for a camera to determine the true hyperfocal distance. A full frame sensor at 0.029 mm yields a different hyperfocal distance than the rounded 0.030 mm, which matters for sharp foreground-to-infinity compositions.
• Portrait Photography: Comparing the CoC of a full frame camera (0.029 mm) with an APS-C body (0.019 mm) shows why larger sensors produce shallower apparent depth of field at equivalent fields of view.
• Large Format Film: Compute CoC for 4x5 or 8x10 sheet film, where 35mm values do not apply. A 4x5 camera has a CoC near 0.109 mm, changing depth of field behavior and requiring different aperture strategies.
• Print Production: The custom visual acuity method determines CoC for actual output conditions. A billboard viewed from 3 meters tolerates a much larger CoC than a gallery print viewed from 250 mm, allowing wider apertures without visible blur.
• Cinematography: Determine CoC for cinema camera sensors such as Super 35 or full frame cinema formats. Accurate CoC values are critical for focus pulling and depth of field preview on set.
• Optical Engineering: Evaluate sharpness criteria for lens design and testing. Different divisor values (1500, 1730, or custom) represent different sharpness standards used in MTF analysis and lens quality evaluation.
• Smartphone Photography: The very small CoC of compact smartphone sensors explains why smartphones have inherently deep depth of field and why computational bokeh is necessary to simulate shallow focus effects.
• Education: Teach students how sensor size, print magnification, viewing distance, and visual acuity interact to define acceptable sharpness. The step-by-step derivation shows how each variable contributes to the final CoC value.