Depth of Field

Depth of Field (DoF) / depth əv feeld /

noun | Camera & Optics

The range of subject distances in front of and behind the focus point that appear acceptably sharp in a recorded or captured image. Depth of field is determined by four variables: aperture, focal length, subject distance, and sensor or film format size. It is one of the most fundamental creative and compositional parameters in cinematography, controlling what the audience sees clearly and what is deliberately softened.

Quick Reference

The Explanation: How & Why

A lens can only focus precisely on a single plane at any given focus distance. Objects on that plane render as sharp points on the sensor. Objects in front of or behind that plane project as small circles of light rather than points. These are called circles of confusion (CoC). When the CoC is small enough to be indistinguishable from a point at the intended viewing size, the object appears acceptably sharp. The depth of field is the range within which the circles of confusion remain below this threshold.

Four variables control DoF, and they interact mathematically:

Aperture has the most dramatic effect. The standard formula uses f-stop: $H = f^2 / (N \times c)$, where $f$ is focal length, $N$ is f-stop, and $c$ is the CoC for your sensor. Opening from f/5.6 to f/1.4 on the same lens roughly reduces DoF by a factor of 16. At 85mm, f/2.8, focused at 10 feet on a Full Frame sensor (CoC = 0.024mm), the total DoF is approximately 6.3 inches. Stop down to f/5.6 and the DoF expands to roughly 25 inches.

Focal length has a compound effect. A 100mm lens at f/2.8 produces significantly shallower DoF than a 24mm at f/2.8, even at equivalent fields of view, because longer lenses have a higher reproduction ratio at the same subject distance.

Subject distance changes DoF asymmetrically. At very close focus distances (macro range), DoF can be just a few millimetres. At far distances, the far limit of DoF extends to infinity once the hyperfocal distance is reached.

Sensor size matters because it changes the CoC value used in the calculation. A Micro Four Thirds sensor (CoC = 0.012mm) produces more DoF than a Full Frame sensor (CoC = 0.024mm) at identical aperture and focal length settings. The ARRI ALEXA 35 has a 27.99mm wide sensor (CoC = 0.0187mm), while standard Super 35 is 24.89mm (CoC = 0.016mm). That 12 percent difference affects every DoF calculation.

A 2024 SMPTE RIS-OSVP study found that traditional CoC values, derived from film-era assumptions, may not accurately represent the usable DoF of modern digital cinema cameras. The committee is developing updated optical models for virtual production and VFX workflows.

For a deeper technical breakdown of the math behind these calculations, see the Depth of Field in Cinema guide on the blog.

Historical Context & Origin

The creative use of DoF as a compositional variable is closely linked to two opposing aesthetic traditions. Deep focus cinematography was developed and championed by Gregg Toland in Citizen Kane (1941) and The Best Years of Our Lives (1946). Toland used small apertures and wide-angle lenses to maintain focus from extreme foreground to extreme background, creating compositions in which spatial depth carried narrative and psychological weight. The ASC Manual documents the formulas Toland relied on, which remain the basis for modern DoF calculation.

The opposite tradition - shallow DoF used to isolate and direct attention - became associated with the romantic, intimate visual language of directors including David Lean and cinematographers including Freddie Young. Modern digital cinematography has favoured shallow DoF, in part because early digital video cameras had small sensors that produced deep DoF by default. Large-sensor cameras like the ARRI ALEXA, RED, and Sony VENICE were embraced partly for their ability to produce the shallow DoF associated with 35mm film.

How It's Used in Practice

Scenario 1 - Close-Up Isolation (DP / 1st AC): For a close-up of the protagonist during a key emotional moment, the DP sets an 85mm T1.4 prime on an ARRI ALEXA Mini LF (Full Frame, 36mm sensor width, CoC = 0.024mm), focused at the eyes at 5 feet. The total DoF at this setting is approximately 1.5 inches. The 1st AC places depth marks on the floor at 4-foot-11 and 5-foot-1 to give the actor a safe zone. The background - a busy street - falls into smooth defocus. The shallow DoF removes the background as a visual distraction and places the full weight of the image on the performance.

Scenario 2 - Environmental Context (DP): A scene requires the audience to read both a character in the foreground and a key piece of narrative information on a wall in the background simultaneously. The DP sets a 21mm lens at T8 on a Super 35 sensor (CoC = 0.016mm), which provides a DoF extending from 3 feet to infinity at a 6-foot subject distance. Both the character and the background object are sharp. The deep DoF communicates that both elements carry equal narrative weight.

Scenario 3 - Documentary Follow Focus (Solo DP): A solo documentary cinematographer needs enough DoF to follow an unpredictable interview subject who moves forward and back without a focus puller. They use the DoF Calculator to find the widest aperture that gives 24 inches of DoF at 6 feet on a 24mm lens on a Full Frame sensor. The result: f/5.6. They adjust exposure with ND filters rather than aperture, preserving the DoF across the subject's movement range.

Usage Examples in Sentences

"At T1.4 and 85mm, the depth of field is less than an inch at this distance - the AC needs marks for every beat."

"Stop down to T8 and put both the foreground character and the background sign in focus - I need the audience to see both."

"The DoF on a Full Frame sensor at T2 is noticeably shallower than Super 35 at the same stop - factor that in when choosing lenses."

"The 1st AC pulled focus from 15 feet to 4 feet on a 50mm at T2.8; the DoF at the close position was only 4 inches, so the move was rehearsed four times before the take."

Common Confusions & Misuse

Depth of Field vs. Depth of Focus: Depth of field is the range of object distances that appear sharp in the image (measured in front of the lens, in object space). Depth of focus is the range of sensor or film plane positions that produce an acceptably sharp image of a fixed object (measured behind the lens, in image space). Depth of focus is an engineering parameter relevant to lens and camera design; depth of field is the production and creative parameter. They are frequently confused because the names are similar, but they operate at different ends of the optical chain.

Depth of Field vs. Bokeh: Bokeh is the quality and character of the out-of-focus areas in an image - the smoothness, shape, and color rendering of the circles of confusion produced by a specific lens. DoF describes how much of the scene is sharp; bokeh describes how the unsharp areas look. A lens can produce very shallow DoF with unpleasant, hard-edged bokeh, or the same DoF with smooth, creamy bokeh. Both are different aspects of lens performance.

Sensor size does not directly change DoF physics: A common claim is that larger sensors produce shallower DoF. At the same aperture, focal length, and subject distance, the sensor itself does not change the physics of DoF. The shallower look comes from the fact that you typically use a longer focal length or move closer to match framing on a larger sensor. The sensor changes the CoC value and the framing decisions that lead to different shooting distances.

Variations by Context

Key People & Films

Gregg Toland pioneered deep focus cinematography on Citizen Kane (1941) and The Best Years of Our Lives (1946), using small apertures, wide-angle lenses, and specially coated optics to hold foreground and background in simultaneous sharpness. Janusz Kaminski applied the opposite approach for Spielberg on Schindler's List (1993) and Saving Private Ryan (1998), using shallow DoF to isolate subjects within chaos. Roger Deakins used shallow DoF on Blade Runner 2049 (2017) with the ARRI ALEXA XT to control attention in visually complex environments. Hoyte van Hoytema shot Tenet (2020) on a large-format IMAX-compatible camera, where the enormous sensor produced extremely shallow DoF that demanded precise focus pulling at T1.4 equivalents.

Equipment / Tools Reference

The ARRI ALEXA 35 (Super 35, 27.99mm sensor width) and ALEXA Mini LF (Large Format, 36mm sensor width) are the most common cinema cameras in current production; their different sensor sizes produce measurably different DoF at the same lens and stop. The Sony VENICE 2 offers a dual-format sensor (Super 35 and Full Frame modes), allowing DPs to switch CoC values within one camera body. Cinema prime lens sets from Cooke (S7/i, Panchro/i), Zeiss (Supreme Prime, CP.3), and ARRI (Signature Prime) all publish T-stop and corresponding f-stop data in their spec sheets for DoF calculations. The Depth of Field Calculator and Circle of Confusion Calculator on this site handle the math for any sensor, lens, and aperture combination.

Standards & Specifications

The ASC Manual, 10th Edition defines the standard cinema CoC as sensor width divided by 1500. Zeiss publishes a tighter formula (sensor diagonal / 1730) for their cinema-spec lenses. The SMPTE RIS-OSVP Camera and Lens Metadata Committee is conducting ongoing studies (2024-present) to validate updated optical models for digital cinema cameras, as traditional film-era CoC values may not accurately represent usable DoF on modern sensors. For 4K delivery, a divisor of 2000 is recommended; for 8K delivery, 3000. The hyperfocal distance formula $H = f^2 / (N \times c) + f$ is documented in both the ASC Manual and ISO photography standards as the basis for all DoF calculation.

Common Questions / FAQ

Q: How do I calculate depth of field without a calculator?

A: Use the hyperfocal distance formula: $H = f^2 / (N \times c)$, where $f$ is focal length in mm, $N$ is f-stop, and $c$ is the CoC for your sensor. Near limit = $H \times s / (H + (s - f))$, far limit = $H \times s / (H - (s - f))$, where $s$ is subject distance. In practice, most cinematographers use a DoF app or the calculator on this site rather than computing by hand.

Q: Does a Full Frame sensor give less depth of field than Super 35?

A: At the same aperture, focal length, and subject distance, the sensor itself does not change the physics of DoF. The shallower look comes from using a longer focal length or moving closer to match framing on the larger sensor. The sensor changes the CoC value and the framing decisions that lead to different shooting distances.

Q: What f-stop gives cinematic shallow depth of field?

A: There is no single "cinematic" f-stop, but T1.4 to T2.8 on a fast prime at 50mm or longer on a Super 35 or Full Frame sensor will produce visibly shallow DoF in close-ups. The look depends on subject distance, focal length, and sensor size working together, not aperture alone.

Q: Should I use T-stop or f-stop for DoF calculations?

A: 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 gives the corresponding f-stop. The difference is usually small (T1.4 might be f/1.3) but matters at wide apertures.

Related Terms

• Aperture - The primary control for DoF; wider aperture gives shallower depth. Measured in f-stops (geometric) or T-stops (transmission).
• Shallow Depth of Field - A specific application: deliberately using shallow depth for subject isolation and background separation.
• Deep Focus Shot - A specific application: deliberately using deep DoF to hold multiple planes sharp simultaneously.
• Lens - Focal length is the second DoF control after aperture; longer focal lengths produce shallower DoF at the same stop and distance.
• Focus - The specific plane within the DoF that is rendered with maximum sharpness; the center of the acceptable sharpness range.
• Racking Focus - A focus pull during a shot that deliberately exploits shallow DoF to transfer attention between subjects.

See Also / Tools

Use the Depth of Field Calculator to apply this concept instantly - input your sensor, focal length, aperture, and subject distance to get exact near limit, far limit, and total DoF. For the theory behind how sensor format affects DoF, see Depth of Field in Cinema in the blog. For anamorphic workflows, use the Anamorphic Desqueeze Calculator alongside DoF calculations, and the Circle of Confusion Calculator to get the correct CoC for your specific sensor and delivery format.

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