What is depth of field?

Depth of field is the range of distances that appear acceptably sharp in the final image. It is not a hard boundary, it is a judgement based on a circle of confusion, which is how large a blurred point can be before a viewer notices. Larger sensors, longer lenses, wider apertures and closer subjects all reduce it.

Why is my footage soft when I shoot wide open?

Usually because the depth of field is smaller than your subject moves. At T1.5 on a 55mm Super 35 lens focused at two metres, the total depth can be under fifteen centimetres. A person shifting their weight moves further than that, which is why narrative work employs a focus puller rather than trusting the mark.

Does sensor size change depth of field?

Yes, at matched framing. A full frame sensor needs a longer lens than micro four thirds to frame the same shot from the same position, and the longer lens gives less depth of field at the same f-number. That is why smaller formats are described as deeper, and why full frame is easier to make look shallow.

What circle of confusion should I use for video?

A common convention is the sensor diagonal divided by 1,500, which for full frame gives about 0.029mm. Video is more forgiving than large print because the delivery resolution is lower, but 4K delivery on a large screen is closer to a stills standard than to old broadcast, so it is safer to use the stricter figure.

Should I stop down to make focus easier?

Often yes, and it is underused advice. Going from T1.5 to T2.8 roughly doubles the depth of field, which turns a nearly impossible pull into a manageable one. Add light rather than opening the lens, because a scene lit for T2.8 gives you focus margin that no amount of skill can otherwise buy.

How much focus margin should a documentary shooter leave?

Enough that a subject can shift naturally without going soft, which usually means shooting between f/2.8 and f/4 rather than wide open. Autofocus systems are good but they hunt when the depth is razor thin and the subject moves unpredictably. Deeper focus is a reliability decision, not an aesthetic compromise.

Depth of Field Calculator for Video

Short answer

Depth of field shrinks with a larger sensor, a longer lens, a wider aperture and a closer subject. A 55mm lens at T1.5 on Super 35 focused at two metres holds roughly 12 to 15 centimetres of total depth, which is less than a person shifts their weight.

Depth of field is the number that decides whether a shot is usable, and on fast cine glass it is far smaller than people expect. When the margin gets that thin, focus stops being a setting and becomes a job, which is why the Tilta Nucleus Nano II Base Kit at around $299 appears on every narrative build we publish.

Calculator

Runs in your browser

Set the format, lens, aperture and subject distance. The readout gives the near and far limits of acceptable sharpness, the total depth, and the hyperfocal distance for that combination.

Sensor format

Focal length in mm

Aperture, f or T number

Subject distance in metres

Total depth of field

0 cm

in front, behind

Sharp from

0 m

to far limit

Hyperfocal distance

0 m

focus here for max depth

What this means on set

The formulas

Depth of field uses the hyperfocal distance as its foundation: H = (focal squared) / (aperture x circle of confusion) + focal.

From that, the near limit is (distance x (H - focal)) / (H + distance - 2 x focal) and the far limit is (distance x (H - focal)) / (H - distance). When the subject distance reaches the hyperfocal distance, the far limit becomes infinity.

The circle of confusion used here is the sensor diagonal divided by 1,500, which is a standard convention. Full frame gives about 0.029mm and Super 35 about 0.019mm. A stricter figure produces a smaller depth of field, so treat any calculator result as a guide and confirm on a monitor.

The four variables, ranked by how much they matter

Change	Effect on depth of field	Practical note
Halve the subject distance	Depth reduces roughly fourfold	The strongest lever, and the one people forget
Double the focal length	Depth reduces roughly fourfold at the same distance	But you usually step back, which partly offsets it
Open up two stops	Depth roughly halves per stop	The easiest thing to change on set
Move to a larger sensor	Depth reduces at matched framing	Full frame is about one stop shallower than Super 35

Real numbers for narrative work

On Super 35 with a 55mm lens focused at two metres, T1.5 gives roughly 12 to 15 centimetres of total depth. That is the distance an actor covers by leaning forward to make a point. At T2.8 the same shot holds roughly 25 centimetres, and at T4 roughly 35 centimetres.

This is why "just stop down and add light" is the most useful advice in this whole area. Two stops of extra light on a subject buys you double the focus margin, and a amaran 200x S Bi-Colour COB through a softbox is a cheaper solution to soft footage than any focus system.

What to do when the margin is too thin

Focus systems, in order of what they solve

A marked manual wheel for repeatable pulls, a wireless wheel so a second person can do the job, and LiDAR autofocus for solo operators on manual glass.

Starter pick $59

Tilta

Tilta Pocket Follow Focus

A geared manual wheel with A and B stops and fluid damping on a 15mm rod clamp, which is the whole job for a fraction of a wireless system.

Type: Manual, geared
Mount: 15mm rod

Manual only, and that is often the right answer.

Check price

Best value $299

Tilta

Tilta Nucleus Nano II Base Kit

A hand wheel and one motor, which is the cheapest complete wireless focus system that a second person can actually pull with.

Type: Wireless
Motors: 1 included

The pick the moment a focus puller joins you.

Check price

Expert choice $999

DJI

DJI Focus Pro Creator Combo

LiDAR autofocus with a motor and grip, which lets one person hold focus on manual cine glass, and that is a genuinely new capability rather than a nicer wheel.

Focus: LiDAR, 20 m

The answer for solo narrative work on manual lenses.

Check price

The Tilta Pocket Follow Focus gives you marked A and B stops, which is the whole technique of narrative focus: mark the start, mark the end, rehearse the move. The Tilta Nucleus Nano II Base Kit adds a wheel a second person can use from where they can see the subject. The DJI Focus Pro Creator Combo replaces the second person entirely with LiDAR ranging, which is genuinely new capability rather than a nicer wheel.

The focus pulling guide covers the marking technique and how a puller actually works, and the monitoring guide covers peaking and punch-in for checking focus without a puller.

Documentary work: deeper on purpose

Run and gun shooters should treat depth of field as a reliability setting rather than an aesthetic one. Autofocus systems are good, and they hunt when the depth is razor thin and a subject moves unpredictably. Shooting at f/2.8 to f/4 rather than wide open gives the system enough margin to stay locked, and the difference in background separation is far smaller than the difference in usable takes.

That is one of several reasons the working run and gun build pairs a fast zoom with the expectation that you will not shoot it wide open all day.

Focus breathing, the related problem

Focus breathing is the change in field of view as a lens focuses, and it is separate from depth of field but shows up in the same shots. A lens that breathes badly makes a focus pull look like a subtle zoom, which is distracting in a scripted scene and largely invisible in a documentary interview. Cine lenses are designed to minimise it, and that is a real part of what the price buys.

Worked example: a two person dialogue scene

Two actors, one at 2.0m and one at 2.6m, shot on Super 35 at 55mm. At T1.5 the total depth is around 13 centimetres, so only one of them can be sharp, and the shot requires a pull between them. At T4 the depth is roughly 35 centimetres, which still does not hold both, and at T5.6 it approaches half a metre and the shot becomes possible without a pull.

Neither approach is wrong. The point is that the aperture decision and the blocking decision are the same decision, and calculating it before the day means you light for the stop you need rather than discovering it on set.

Next, from here

Hyperfocal distance calculator
Where to focus for maximum usable depth.
Crop factor and field of view
How format changes the lens you need.
Best follow focus systems
Manual, wireless and LiDAR.
Focus pulling guide
Marking, rehearsing and executing a pull.
Best cine lenses
T stops, breathing and gearing.
Narrative working build
A rig built around a focus puller.

Common questions

What is depth of field?: Depth of field is the range of distances that appear acceptably sharp in the final image. It is not a hard boundary, it is a judgement based on a circle of confusion, which is how large a blurred point can be before a viewer notices. Larger sensors, longer lenses, wider apertures and closer subjects all reduce it.
Why is my footage soft when I shoot wide open?: Usually because the depth of field is smaller than your subject moves. At T1.5 on a 55mm Super 35 lens focused at two metres, the total depth can be under fifteen centimetres. A person shifting their weight moves further than that, which is why narrative work employs a focus puller rather than trusting the mark.
Does sensor size change depth of field?: Yes, at matched framing. A full frame sensor needs a longer lens than micro four thirds to frame the same shot from the same position, and the longer lens gives less depth of field at the same f-number. That is why smaller formats are described as deeper, and why full frame is easier to make look shallow.
What circle of confusion should I use for video?: A common convention is the sensor diagonal divided by 1,500, which for full frame gives about 0.029mm. Video is more forgiving than large print because the delivery resolution is lower, but 4K delivery on a large screen is closer to a stills standard than to old broadcast, so it is safer to use the stricter figure.
Should I stop down to make focus easier?: Often yes, and it is underused advice. Going from T1.5 to T2.8 roughly doubles the depth of field, which turns a nearly impossible pull into a manageable one. Add light rather than opening the lens, because a scene lit for T2.8 gives you focus margin that no amount of skill can otherwise buy.
How much focus margin should a documentary shooter leave?: Enough that a subject can shift naturally without going soft, which usually means shooting between f/2.8 and f/4 rather than wide open. Autofocus systems are good but they hunt when the depth is razor thin and the subject moves unpredictably. Deeper focus is a reliability decision, not an aesthetic compromise.

Totalling your own rig weight against your gimbal payload? The Camera Rig Build Planner is the paid version of these pages: 8 printable worksheets you fill in with your own numbers, plus the full PDF, $29.