What Circle of Confusion Value Should You Actually Use? A Sensor-by-Sensor Guide

The Default Nobody Tells You About

Open almost any depth of field calculator app. Enter focal length, aperture, and focus distance. The calculator returns a sharp zone. What it does not tell you -- unless you dig into the settings -- is which circle of confusion value it used to produce that number. Some apps hard-code 0.029mm for every camera. Others use 0.025mm for anything labelled "cinema." A handful use 0.030mm as a blanket film standard. The number you never chose is doing most of the work.

The practical consequence: two DPs on the same production, using different apps on the same lens and the same camera, may get meaningfully different DoF numbers from the same inputs. Neither app is necessarily wrong in isolation -- they are using different hidden CoC defaults. But only one of those defaults matches the sensor format actually in the camera.

This post explains what default values popular DoF tools use, why those defaults diverge, how to identify which value your tool is using, and which value to apply for every major cinema and mirrorless sensor in production use today.

The CoC values in this post are calculated from the sensor diagonal / 1500 formula used in the ASC Manual and in most lens manufacturer depth of field charts. Where published manufacturer-specified values exist, those are noted alongside the calculated figure.

Why Calculators Disagree: The Hidden Default Problem

The circle of confusion formula divides sensor diagonal by a viewing-distance standard. The industry-standard divisor is 1500, based on an 8x enlargement to a 25 x 30cm print viewed at 25cm. Some calculators use 1442 or 1730 instead, based on different assumptions about print size or viewing distance. A calculator using 1730 produces a CoC approximately 13% smaller than one using 1500 -- and therefore a DoF prediction roughly 13% narrower from the same inputs.

The second source of divergence is how calculators handle sensor labels. When you select "Super 35" from a dropdown, the app must decide which sensor dimensions correspond to that label. Super 35 encompasses at least three meaningfully different physical sizes: the ARRI ALEXA 35 Open Gate (27.99 x 19.22mm), the ARRI ALEXA Mini LF Super 35 extraction (26.67 x 14.99mm), and a generic 4-perf Super 35 reference (24.89 x 18.66mm). Each produces a different diagonal, a different CoC, and a different DoF prediction -- yet all three may appear under the same "Super 35" dropdown entry in different apps.

A third issue is apps that have not been updated since digital cinema sensor sizes changed. A calculator written in 2015 may use Super 35 dimensions calibrated for cameras that have been discontinued, producing values that do not match any currently shipping camera. The fix is to enter a manual CoC calculated from your camera's actual spec sheet rather than selecting from any dropdown.

Common Default CoC Values and Where They Come From

0.033mm -- 35mm film standard, used in the original ASC Manual and in virtually all lens depth of field scales manufactured before 2010. This value is correct for 35mm Academy aperture projection and is still technically valid for shooting on 35mm film. It is wrong for every digital sensor.

0.029mm -- Full Frame digital standard, calculated as 43.3mm diagonal / 1500. Correct for Sony VENICE 2, Sony FX3, Canon EOS C70 in Full Frame mode, ARRI ALEXA LF, and all 35.9 x 24.0mm sensors. Many apps use this as a blanket default regardless of sensor mode -- it is the single most common incorrect default applied to Super 35 cameras.

0.025mm -- A compromise value sometimes used as a "cinema" default, falling between Full Frame (0.029mm) and Super 35 (0.019-0.023mm). It is not precisely correct for any current production camera but is less wrong than 0.029mm for Super 35 work.

0.019mm -- Correct for Sony APS-C sensors (23.5 x 15.6mm, diagonal 28.2mm / 1500). Also used as a generic Super 35 value in some apps, though the actual correct value for Super 35 depends on the specific camera and extraction mode.

0.015mm -- Correct for Micro Four Thirds sensors (17.3 x 13.0mm, diagonal 21.6mm / 1500).

Three Cases Where the Default Caused a Real Problem

Example 1: A-Camera Operator Using a Full-Frame Default on Super 35

A focus puller on a Sony FX9 Super 35 crop shoot uses a popular iOS DoF app that defaults to Full Frame (0.029mm) because the app was last updated before Super 35 crop modes were common. The app returns a DoF of 9.4 inches at 6 feet, T2.0, 50mm. The correct CoC for the FX9 Super 35 crop (23.5 x 12.7mm, diagonal 26.8mm) is 0.018mm. The correct DoF is 5.8 inches. The 3.6-inch gap is enough for a subject's near eye to be sharp while the far eye falls outside the actual sharp zone.

Example 2: Two 1st ACs on Matching Bodies Getting Different Numbers

A multi-camera commercial uses two ARRI ALEXA 35 bodies in Open Gate mode with a 1.78:1 Super 35 extraction. 1st AC on Camera A uses an app that defines "ALEXA 35" as the full Open Gate sensor (27.99 x 19.22mm, CoC = 0.023mm). 1st AC on Camera B uses an app with a generic "ALEXA" preset calibrated to the older ALEXA Mini dimensions (26.67 x 14.99mm, CoC = 0.020mm). Both are running the same lens at the same distance. At T2.8 and 8 feet, Camera A's operator expects 21 inches of DoF; Camera B's operator expects 18 inches. The intercutting in post reveals a subtle but visible difference in how aggressively the background falls off.

Example 3: Mirrorless Operator Assuming App Is Correct

A documentary DP shooting on a Blackmagic Pocket Cinema Camera 6K G2 in the 6K Super 35 mode (23.1 x 12.99mm, diagonal 26.8mm, CoC = 0.018mm) opens a DoF app that defaults to Micro Four Thirds (0.015mm) because the previous version of that app only supported the original BMPCC which was MFT-native. At T1.8 and 5 feet with a 35mm lens, the app returns 5.3 inches. The correct value at 0.018mm is 6.4 inches. The subject in the frame has more usable DoF than the operator thinks -- not a disaster, but an inaccuracy that affects every focus decision made that day.

Correct CoC by Sensor Format: The Reference Table

The table below shows calculated CoC values for current production sensors. Use these to verify or override whatever default your DoF app uses.

The ARRI ALEXA LF Open Gate produces a larger CoC (0.036mm) than Full Frame because its sensor is physically larger than a standard 35.9 x 24.0mm Full Frame. This is why LF lenses produce even shallower depth of field than Full Frame glass at equivalent focal lengths and apertures.

How to Find and Override the Default in Your DoF App

Step 1: Open your DoF app and look for a "CoC," "sensor," or "camera" settings panel. In iOS apps like pCAM, Artemis Director's Viewfinder, or Simple DoF, this is usually one tap from the main calculation screen.

Step 2: If the app shows a numeric CoC field, read the current value before entering your inputs. If it shows 0.029mm for a camera you know is Super 35, it is using the wrong default.

Step 3: Replace the default with the correct value from the table above. Use the Circle of Confusion Calculator to compute a custom value if your specific camera mode is not in the table -- enter the active image area dimensions from the manufacturer's spec sheet.

Step 4: If the app does not expose the CoC as an editable field (some consumer apps lock it), use a different tool. The Depth of Field Calculator allows manual CoC entry for any sensor format.

Step 5: Make a note of the correct CoC for your production camera mode and set it once at the start of each day. If the camera mode changes (switching from Full Frame to Super 35 crop on a Sony FX9), update the CoC before running new calculations.

Pro Tips and Common Mistakes

Pro Tip: If you are unsure which CoC value an app is using, run a quick sanity check. Enter a 50mm lens at T2.8 and 10 feet. Full Frame (0.029mm) should return approximately 24 inches of DoF. Super 35 (0.019mm) should return approximately 16 inches. If your app returns the Super 35 number while you have "Full Frame" selected, or vice versa, it is using a different CoC than expected.

Pro Tip: For the most reliable on-set DoF reference, build a printed DoF table before the shoot using the correct CoC for your specific camera mode. Run the Depth of Field Calculator for each lens in your kit at each likely aperture and focus distance, and print the results. A physical table eliminates the risk of a wrong default mid-day when there is no time to check app settings.

Pro Tip: When sharing a DoF setup between two operators on different apps, agree on a single CoC value before shooting begins and confirm both apps are using it. A quick verbal check -- "I'm running 0.020mm, what are you on?" -- takes 10 seconds and eliminates inter-operator inconsistency.

Common Mistake: Updating a DoF app and not re-checking the default CoC afterward. App updates sometimes reset custom settings to factory defaults. The reset may not be announced in the update notes. Make a habit of verifying the CoC setting at the start of any production where a new app version has recently installed.

Common Mistake: Using a lens manufacturer's published DoF table without checking which CoC it was calculated for. Cooke, ARRI, and Zeiss publish physical DoF tables for their cinema lenses -- but those tables may be calculated at 0.025mm or 0.030mm rather than the sensor-specific CoC for your camera. Read the footnote on any published table before trusting it.

Frequently Asked Questions

Why do different manufacturers specify different CoC values for the same sensor size?

Some manufacturers calculate CoC using 1/1730 of the diagonal (a stricter standard based on 1/30mm per mm of enlargement) while others use 1/1500. ARRI has published specific CoC recommendations for their sensor formats. Zeiss and Cooke have historically used slightly different standards for their printed DoF scales. The difference is small in absolute terms but accumulates at wide apertures and close subject distances.

Should I use a stricter CoC for 4K or 8K cameras?

Theoretically, higher sensor resolution warrants a smaller CoC because the sensor can resolve finer detail, tightening the threshold for what appears acceptably sharp. In practice, most cinematographers still use the diagonal / 1500 standard regardless of resolution, because delivery formats, compression, and viewing conditions rarely deliver the full resolution to the viewer's eye. Using a stricter CoC (smaller number) on 8K cameras produces more conservative DoF predictions -- a reasonable choice if your production is delivering for large-screen theatrical exhibition.

If I always shoot Full Frame, do I need to worry about this?

Only if your camera has multiple sensor modes. Sony FX3, FX9, and VENICE 2 all offer Full Frame and cropped modes. The FX9 in particular is frequently switched between Full Frame and Super 35 crop during a shoot day, and an app that does not track that switch will use the wrong CoC for whichever mode was not most recently confirmed. If your camera only ever shoots in one mode at one sensor size, set the CoC once and do not change it.

Can I get away with using 0.025mm as a universal cinema default?

It depends on the production. For run-and-gun documentary work where exact DoF limits are used as guides rather than hard lines, 0.025mm is accurate enough for Full Frame and conservative enough for Super 35. For narrative work with a dedicated focus puller managing exact near and far limits, using the wrong CoC by 30% is not acceptable. Use the correct sensor-specific value.

Related Tools

The Circle of Confusion Calculator computes the correct CoC from any sensor dimensions you enter, including unusual extraction modes not covered by standard dropdowns. The Depth of Field Calculator accepts a manual CoC input so you are never dependent on a dropdown's hidden default. For matching DoF across different sensor formats on multi-camera productions, the Camera Sensor Crop Calculator handles the format geometry alongside the CoC implications.

For the full explanation of how CoC feeds into the depth of field formula, What Circle of Confusion Should You Use for Your Camera? covers the derivation with worked examples. For how the resulting DoF numbers compare against what is physically marked on lens barrels, DoF Calculator vs. Lens Markings: Which to Trust on Set? covers the discrepancy and when it matters.

Check the Number Before You Trust the Output

A DoF calculator is only as accurate as the CoC it uses. The number that changes most often and matters most -- the circle of confusion -- is also the number most DoF apps never surface in normal use. Confirm your app's default against your sensor's actual dimensions once at the start of each production. When in doubt, enter a manual value from the table above rather than accepting a dropdown preset. Every near/far limit and hyperfocal distance you generate from that point will be built on a verified foundation.

This post covers single-camera digital productions. Film camera applications, optical viewfinder work, and special-format productions involve additional CoC considerations not covered here. What CoC default has surprised you most on a production, and how far off was the resulting focus decision?