Introduction
You're on set at call time. The DP has chosen an 85mm T1.4 on the ALEXA Mini LF, and the first shot of the day is a tight two-shot where both actors need to be sharp. Your gaffer asks how close the actors can stand before the far one goes soft. You need a number, not a feeling.
The depth of field calculator removes the guesswork. Enter your sensor size, focal length, aperture, and subject distance, and it returns your near and far focus limits alongside your total depth of field in feet or meters, whichever you pull focus in. No charts. No mental math on set.
Understanding what the calculator is actually doing, and why the numbers change the way they do, makes you faster and more confident whether you're pulling on a full-frame sensor or a Super 16.
What This Tool Calculates
The calculator takes four inputs: sensor size (the width of your camera's imaging area in millimeters), focal length of the lens in millimeters, aperture expressed as an f-stop or T-stop, and subject distance in meters or feet.
It returns four outputs. Near focus limit is the closest point to the camera that still appears acceptably sharp. Far focus limit is the farthest point from the camera that remains sharp. Total depth of field is the distance between those two limits. Hyperfocal distance is the focus distance at which everything from half that distance to infinity falls within acceptable sharpness.
The Formula and How It Works
The calculator uses the hyperfocal distance equation, as defined in the ASC Manual (American Society of Cinematographers): H = (f squared) / (N times c) + f, where f is the focal length in millimeters, N is the f-stop number, and c is the circle of confusion.
The circle of confusion (CoC) represents the largest blur spot that the human eye still perceives as a point. For cinema work, the standard CoC is typically calculated as the sensor width divided by 1500. For a Full Frame sensor at 36mm wide, that gives a CoC of 0.024mm. For Super 35 at 24.89mm wide, the CoC is roughly 0.016mm.
Once the hyperfocal distance is known, the near limit equals (H times d) / (H + (d minus f)), and the far limit equals (H times d) / (H minus (d minus f)), where d is the subject distance in millimeters. If d is greater than or equal to H, the far limit extends to infinity.
Worked example: an 85mm lens at f/2.8 on a Full Frame sensor (CoC = 0.024mm) with the subject at 3 meters. H = (85 squared) / (2.8 times 0.024) + 85 = 7225 / 0.0672 + 85 = 107,589mm + 85mm = 107,674mm, or roughly 107.7 meters. Near limit = (107,674 times 3000) / (107,674 + (3000 minus 85)) = 323,022,000 / 110,589 = 2,921mm, or 2.92 meters. Far limit = (107,674 times 3000) / (107,674 minus (3000 minus 85)) = 323,022,000 / 104,759 = 3,083mm, or 3.08 meters. Total DoF = 3.08 minus 2.92 = 0.16 meters, roughly 6.3 inches. That's tight enough to rack focus between two actors seated 6 inches apart.
Real-World Examples
Narrative Close-Up with 85mm on ALEXA Mini LF
A first AC on a period drama needed to hold both the lead actress and a candlestick in the foreground acceptably sharp during a dialogue close-up. The DP selected an 85mm at T2. On the ALEXA Mini LF (Full Frame, 36mm sensor width), with the actress at 1.5 meters, the calculator returned a total DoF of just 3.8cm. The AC requested the props department move the candlestick 2cm closer to the actress, which placed it inside the sharp zone without a split-diopter.
Documentary Run-and-Gun with 24mm on Canon R5
A documentary crew shooting a street protest needed to keep subjects sharp from 2 meters to roughly 5 meters while moving handheld. Using a 24mm lens at f/5.6 on the Canon R5 (Full Frame), the calculator showed a DoF stretching from 1.3 meters to 18.9 meters, well beyond the needed range. The operator stopped down one more stop to f/8 and gained a DoF from 1.02 meters to infinity, essentially zone focusing for the entire shoot.
Commercial Product Shot with 100mm Macro on BMPCC 4K
A tabletop commercial for a watch brand used a 100mm macro lens at T2.8 on the Blackmagic Pocket Cinema Camera 4K (Micro Four Thirds, 17.3mm sensor). The subject distance was 0.4 meters. The calculator returned a total DoF of 1.1mm. The director of photography used this number to determine that focus stacking across 12 frames was necessary to render the entire watch dial sharp in the final composite.
Sensor Size Reference Chart
| Sensor Name | Dimensions (mm) | Circle of Confusion (mm) | Crop Factor |
|---|---|---|---|
| Full Frame | 36 x 24 | 0.024 | 1.0x |
| Super 35 (ARRI) | 24.89 x 18.66 | 0.016 | 1.4x |
| APS-C (Canon) | 22.3 x 14.9 | 0.015 | 1.6x |
| APS-C (Sony/Nikon) | 23.5 x 15.6 | 0.016 | 1.5x |
| Micro Four Thirds | 17.3 x 13.0 | 0.012 | 2.0x |
| Super 16mm | 12.52 x 7.41 | 0.008 | 2.9x |
| 1-inch Sensor | 13.2 x 8.8 | 0.009 | 2.7x |
Pro Tips and Common Mistakes
Pro Tips
- When shooting anamorphic, apply the squeeze factor before your DoF calculation. A 2x anamorphic lens on Super 35 behaves like shooting on a sensor twice as wide horizontally, which changes the effective CoC.
- Use hyperfocal distance charts for run-and-gun work. Set your focus to the hyperfocal distance, and everything from half that distance to infinity stays sharp. Print the chart and tape it to your mattebox.
- T-stops and f-stops differ. A T-stop accounts for light transmission loss through the glass. For exposure, use T-stops. For DoF calculations, use f-stops. Most cinema lenses are marked in T-stops, so check the manufacturer's spec sheet for the equivalent f-stop.
- At distances under 1 meter, the standard DoF formula loses accuracy. Switch to a close-up or macro-specific calculation that accounts for magnification ratio instead.
Common Mistakes
- Using a Full Frame CoC value when shooting on a Super 35 sensor. The smaller sensor has a tighter CoC, which means the calculated DoF is actually narrower than you expect. Always match the CoC to your specific sensor.
- Forgetting to convert units. The formula expects all values in millimeters internally. Entering distance in feet when the formula expects meters produces wildly incorrect results.
- Assuming the DoF is symmetrical. At typical shooting distances, roughly one third of the DoF falls in front of the focus point and two thirds behind it. This ratio shifts as you approach the hyperfocal distance.
Frequently Asked Questions
What is the difference between T-stop and f-stop for depth of field?
T-stop measures actual light transmission through the lens, while f-stop measures the geometric ratio of the aperture. For DoF calculations, use the f-stop because it determines the physical cone of light that creates the blur circle. Most cinema lenses list T-stops on the barrel, but the manufacturer's spec sheet will give you the corresponding f-stop.
How does sensor size affect depth of field?
A larger sensor requires a longer focal length to achieve the same field of view, which narrows the DoF. A Full Frame sensor at 50mm f/2.8 gives a shallower DoF than a Micro Four Thirds sensor at 25mm f/2.8, even though the field of view is identical. The larger sensor's CoC is also larger, but the focal length increase dominates the equation.
Can I use this calculator for anamorphic lenses?
Yes, but you need to adjust for the squeeze ratio. Enter the taking lens focal length as normal. For the sensor width, multiply your actual sensor width by the desqueeze ratio. On a Super 35 sensor with a 2x anamorphic, enter 49.78mm as the sensor width instead of 24.89mm.
What circle of confusion value should I use for 8K delivery?
For 8K output viewed on a large display, use a stricter CoC. Divide the sensor width by 3000 instead of 1500. This halves the permissible blur circle and gives a more conservative DoF estimate that holds up on high-resolution displays.
Why does my depth of field change when I change frame rates?
Frame rate itself does not change DoF. However, changing frame rate often requires changing shutter speed (via shutter angle), which may lead you to adjust aperture to maintain exposure. That aperture change is what alters DoF. The 180-degree shutter rule at 24fps gives 1/48s, while at 60fps it gives 1/120s, potentially requiring a wider aperture and therefore shallower DoF.
Start Calculating
Depth of field is the single most powerful creative tool a DP controls beyond lighting. Knowing your exact near and far limits before you roll saves time, prevents blown takes, and gives you the confidence to push your lens choices further.
Use the calculator above to run the numbers for your next setup. Bookmark this page for on-set reference. What focal length and aperture combination do you find yourself reaching for most on narrative work?
