Introduction
Your depth of field calculator just told you the actor is 2 inches outside the sharp zone, and you're about to ask the gaffer to move a 12K HMI so the DP can stop down half a stop. Before you do, ask yourself: which circle of confusion value is the calculator using? If it's the generic 0.03mm that most phone apps default to, you might be solving a problem that doesn't exist on your specific sensor.
The circle of confusion is the foundation of every depth of field and hyperfocal calculation. Get it wrong and every number downstream is inaccurate. This calculator gives you the precise CoC for any sensor size and any delivery standard, from cinema projection to 8K streaming.
Understanding CoC separates technicians who trust their tools from technicians who understand them.
What This Tool Calculates
The calculator accepts two primary inputs: sensor dimensions (width and height in millimeters, either from a preset list or entered manually) and a CoC viewing standard that determines the divisor used in the calculation.
It returns four outputs. The CoC calculated from the sensor width gives you the value most commonly used in cinema depth of field formulas. The CoC calculated from the sensor diagonal provides the value used in many photography references. The sensor diagonal measurement is displayed for cross-reference. The crop factor relative to Full Frame lets you convert between systems quickly.
The Formula and How It Works
The circle of confusion is calculated as: CoC = sensor dimension / divisor. The ASC Manual uses the sensor width divided by 1500 as the cinema standard. Photography references typically use the sensor diagonal divided by 1500 or 1730.
The divisor represents the assumed viewing conditions. A divisor of 1500 assumes the image is projected or displayed at a size where a blur circle smaller than 1/1500th of the sensor width appears sharp. For 4K delivery, a divisor of 2000 produces a stricter CoC. For 8K, a divisor of 3000 ensures sharpness at extreme magnification.
Worked example: Full Frame sensor at 36mm wide. Cinema standard CoC = 36 / 1500 = 0.024mm. For 4K delivery: 36 / 2000 = 0.018mm. For 8K: 36 / 3000 = 0.012mm. On a Micro Four Thirds sensor (17.3mm wide), the cinema standard CoC = 17.3 / 1500 = 0.0115mm, roughly half the Full Frame value.
Real-World Examples
Matching DoF Calculations to 4K HDR Delivery
A post supervisor on a streaming original noticed soft backgrounds in close-ups that the DP had calculated as sharp using a standard CoC of 0.024mm on the ALEXA Mini LF. The issue was that 4K HDR magnified the image beyond what the standard cinema CoC assumed. Recalculating with a stricter CoC of 0.018mm (divisor of 2000) showed the actual depth of field was 30 percent narrower than originally estimated. The DP adjusted subsequent setups by stopping down half a stop.
Cross-Referencing Lens Charts with Actual Sensor
A rental house provided depth of field charts printed for Super 35 (CoC = 0.016mm), but the production was shooting on the Sony VENICE 2 in Full Frame mode (CoC = 0.024mm). The 1st AC used the calculator to determine the correct Full Frame CoC and discovered the rental house charts underestimated the actual DoF by roughly 50 percent. Without the correction, focus marks would have been unnecessarily conservative.
Large Format IMAX Origination
A VFX supervisor preparing for an IMAX sequence on a 65mm sensor (52.48mm width) needed the CoC for compositing depth passes. The standard cinema CoC for 65mm is 52.48 / 1500 = 0.035mm. However, IMAX projection magnifies the negative far beyond standard cinema, so the team used 52.48 / 3000 = 0.0175mm for their depth-of-field renders, ensuring CG elements matched the real photography on an IMAX screen.
Circle of Confusion by Sensor Size and Standard
| Sensor | Width (mm) | Cinema (d/1500) | 4K (d/2000) | 8K (d/3000) |
|---|---|---|---|---|
| Large Format (65mm) | 52.48 | 0.035mm | 0.026mm | 0.017mm |
| Full Frame | 36.00 | 0.024mm | 0.018mm | 0.012mm |
| Super 35 (ARRI) | 24.89 | 0.016mm | 0.012mm | 0.008mm |
| APS-C (Canon) | 22.30 | 0.015mm | 0.011mm | 0.007mm |
| Micro Four Thirds | 17.30 | 0.012mm | 0.009mm | 0.006mm |
| Super 16mm | 12.52 | 0.008mm | 0.006mm | 0.004mm |
Pro Tips and Common Mistakes
Pro Tips
- Always match your CoC to your actual delivery format. A cinema standard CoC of 0.024mm works for theatrical projection but is too lenient for 4K streaming on a 65-inch display.
- When comparing depth of field between two cameras, ensure both calculations use the same CoC standard. Mixing Full Frame cinema CoC with Super 35 photography CoC produces misleading results.
- The circle of confusion is not a hard line between sharp and blurry. It's a perceptual threshold. Objects slightly outside the calculated DoF may still appear acceptably sharp in motion at 24fps.
- For macro and close-up work, the standard CoC formula loses accuracy. At magnification ratios above 1:4, use the adjusted formula: effective CoC = CoC times (1 + magnification).
Common Mistakes
- Using a photography CoC (typically 0.03mm for Full Frame) in a cinema depth of field calculator. Cinema standards are stricter because projected images are viewed at larger relative sizes.
- Assuming all cameras with the same sensor format have identical CoC values. The ARRI ALEXA 35 has a 27.99mm wide sensor (CoC = 0.0187mm), while standard Super 35 is 24.89mm (CoC = 0.0166mm). That 12 percent difference affects every DoF calculation.
- Ignoring the viewing distance assumption. The CoC divisor of 1500 assumes viewing from a specific distance relative to screen size. If your audience watches on phones at arm's length, a stricter CoC may be warranted.
Frequently Asked Questions
What circle of confusion value should I use for my camera?
Start with the cinema standard: your sensor width divided by 1500. For the ALEXA Mini LF (Full Frame, 36mm), that's 0.024mm. For the ALEXA Mini (Super 35, 24.89mm), it's 0.016mm. If delivering in 4K for streaming, consider dividing by 2000.
Why do different DoF calculators give different results?
Almost always because they use different CoC values. Some apps default to the Zeiss photography standard (diagonal / 1730), others use the cinema standard (width / 1500), and some use a fixed 0.03mm. A 0.024mm versus 0.03mm difference on Full Frame shifts the calculated DoF by roughly 25 percent.
How does circle of confusion relate to pixel size?
The CoC is a perceptual standard, not a sensor-level measurement. However, if the CoC is smaller than the pixel pitch, you've reached the sensor's resolving limit. On most cinema cameras, the standard cinema CoC is 2 to 4 times larger than pixel pitch.
Can I use one CoC value for all my lenses?
Yes. The circle of confusion depends on the sensor and viewing standard, not on the lens. A 24mm and a 135mm lens on the same camera body use the same CoC. The lens affects depth of field through focal length and aperture, but the sharpness threshold is determined by the sensor alone.
Start Calculating
The circle of confusion is a small number with enormous consequences. Every depth of field chart, every hyperfocal table, and every focus distance calculation depends on it. Getting the CoC right for your sensor and delivery format is the first step to trusting your numbers.
Use the calculator above to find the correct CoC for your camera and delivery standard. What CoC value does your current DoF app use, and have you verified it against your actual sensor width?
