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DEPTH CAMERAS, EXPLAINED

A camera that
measures distance.

An ordinary photo is flat. A depth camera records how far away everything is.

A woodland path in morning mist, with trees fading softly into the distance — AI-generated image, not a photograph of a real person or place.

Each pixel holds a distance instead of just a colour. There are three main ways to get it: bend a pattern of light over the scene, time the light's round trip, or compare two views like a pair of eyes.

16.7 nslight's trip to 2.5 m and back

What confuses them?

Keep in mind

Project a pattern
Time the light
Compare two views
Three routes to the same depth map

THE SHORT ANSWER

Three ways
to see depth.

A range image stores a distance in every pixel.
Depth cameras differ in how they get it.

PATTERNS

Bend a pattern of light

Structured light projects stripes, dots or grids onto a scene. A camera to one side sees them deform over each surface, and the shape is worked out from that. Infrared light keeps the pattern invisible.

What confuses them

TIMING

Time the light's round trip

A time-of-flight camera sends out light and times its return. Light from something 2.5 m away is back in about 16.7 nanoseconds, so the electronics must be precise.

See the numbers

TWO VIEWS

Compare two pictures

Stereo cameras work like two eyes, matching the same point in two images. They need no special lighting, but struggle on plain, even surfaces where nothing stands out to match.

How the methods compare

A QUICK TROUBLE CHECK

What could
trip it up?

Pick a situation to see how much trouble it causes a depth camera and why. The bar shows how likely the depth reading is to suffer.

Trouble check

Choose a situationA dim living roomA plain white wallAnother depth camera nearbyMirrors, glass or glossBright sunlight

A dim living roomUsually fine

Structured-light and time-of-flight cameras bring their own light, usually infrared, so they do not depend on the room's lighting.

A plain white wallHard for stereo

Stereo cameras must match the same point in two images, which is difficult in areas of even colour. Pattern and timing cameras do not have this problem.

Another depth camera nearbyCan interfere

Some time-of-flight cameras disturb each other's readings. Taking turns or using different modulation frequencies avoids it.

Mirrors, glass or glossOften wrong

Light can bounce along several paths before it returns, so the measured distance may be greater than the true one. Shiny surfaces also affect pattern-based scanners.

Bright sunlightOften swamped

Even after filtering, sunlight on a 1 m² scene can be about 50 times stronger than a typical 1 watt camera light. Ambient light also affects structured-light accuracy.

Sources: Wikipedia articles on time-of-flight cameras, structured-light 3D scanners and range imaging.

General behaviour of each method; individual devices handle these cases in different ways.

TWO NUMBERS WORTH KNOWING

Very fast light,
very bright sun.

One figure on how short the timing is,
one on why outdoor depth sensing is hard.

≈ 16.7 ns

Delay for an object 2.5 m away

Light travels at 299,792,458 metres per second, about 30 cm in a nanosecond. A timing slip of just 10 picoseconds between light and sensor shifts the measured distance by 1.5 mm.

ROUND TRIP · TIME OF FLIGHT

≈ 50× stronger

Sun vs a 1 W camera light, after filtering

Sunlight delivers about 1050 watts per square metre, around 50 watts after the camera's band-pass filter. A typical time-of-flight light source gives about 1 watt.

SUNLIGHT · BACKGROUND

Time-of-flight camera accuracy is usually estimated at about 1% of the measured distance, and some cameras capture up to 160 depth frames a second.

FOUR HABITS FOR CLEANER DEPTH

Help the camera
see the room.

Whether it is a gesture game, a scanner or a robot, these follow from how the methods work.

A hand raised in an open-palm wave in a dim living room, seen from over the person's shoulder — AI-generated image, not a photograph of a real person or place.

Step 1

Keep strong sun off the scene

Draw a blind if sunlight falls where the camera is looking: it can swamp the camera's own infrared light.

Step 2

Cover or move big mirrors

Reflections send light along extra paths and can make objects read further away than they are.

Step 3

Run one camera at a time

Some time-of-flight cameras interfere with each other. If two point at the same space, switch one off.

Step 4

Expect gaps on plain surfaces

Two-lens cameras need detail to match between their images. Areas of plain, even colour are hard to match, so depth there may be missing or unreliable.

HOW THE METHODS COMPARE

Compact, simple,
or passive.

A plain white vase in a dark studio with thin stripes of projected light bending around its curves — AI-generated image, not a photograph of a real person or place.

A time-of-flight camera is compact: the light sits right next to the lens, with no need for the wide spacing that stereo and triangulation set-ups require, and no moving parts. Working out distance from its signal takes little processing.

Stereo needs no special lighting, but matching points between two images is hard, so it often gives reliable depth for only some of the scene. Structured light gets depth from a single image of the pattern, but relies on its projector being seen clearly.

Questions

Questions on the way

What is a depth camera?

A camera whose image stores the distance to each point instead of, or as well as, its colour. It is also called a range camera, and the picture it makes is a range image or depth map.

What is the difference between structured light and time of flight?

Structured light projects a known pattern and works out shape from how it deforms on surfaces. Time of flight times how long light takes to reach the scene and come back.

Why do depth cameras use infrared light?

Infrared keeps the light unobtrusive: the pattern or pulses are invisible to people and do not get in the way of other camera tasks that use visible light.

Do depth cameras work outdoors?

It is harder. Sunlight can be around 50 times stronger than a typical camera's own light even after filtering, although some short-pulse laser systems avoid the problem and are used in space and considered for cars.

Why do phones have depth sensors?

Several phones include time-of-flight sensors, mainly to tell the camera software which parts of a scene are foreground and which are background.

Destination

Where the facts come from

Updated 19 October 2026

A camera thatmeasures distance.

Three waysto see depth.