Lens compression: how focal length and distance change backgrounds and faces

A telephoto lens does not squeeze space. Stepping back does. Telephoto compression and background compression come from that change of distance: the longer lens only keeps the person the same size from farther away, which makes the background look larger and the face look calmer.

Compression and face lab

Mode

Focal length135 mm Framing at 50 mm Background behind the person4.50 m

Top view. Gold is 24 mm. Green is the focal length you chose. In the matched-size view both wedges pass through the same shoulder width, so the longer lens sees a narrower slice of the wall.

Camera distance: 5.40 m; versus 0.96 m at 24 mm
Visible background width: 2.64 m; 3.10× larger background than 24 mm
Horizontal angle of view: 15.2°; versus 73.7° at 24 mm
Nose versus ears: +2.2 %

Compare 24 mm and 135 mm side by side in the 3D portrait simulator

What do you want the picture to do?

Most portrait choices are one of these three.

A flattering portrait
Step back to about 1.5 m to 2.5 m and use 85 mm to 135 mm. On APS-C that is about 56 mm to 90 mm.
Open 24 mm against 85 mm, same head size
A huge background
Use 135 mm or 200 mm and step back until the person is the size you want. The background then grows by more than 3×.
Open 35 mm against 200 mm
A tight room
Use 35 mm for a half-length or full-length portrait, from about 1.4 m to 2.5 m, and keep the face near the middle of the frame.
Open 35 mm against 50 mm indoors

Why stepping back magnifies the background

At 24 mm you stand 0.96 m from the person so the frame matches a 50 mm lens at 2.00 m. A wall 4.50 m behind the person is then 5.46 m from the camera, about 5.7 times farther than the person. The 73.7° view takes in 8.19 m of that wall.

At 135 mm you stand 5.40 m away for the same person size. The same wall is 9.90 m from the camera, less than twice as far as the person. The 15.2° view takes in only 2.64 m of wall and spreads that strip across the whole frame. The background looks 3.10× larger than it did at 24 mm.

Why a wide lens distorts a face

The tip of the nose sits about 12 cm in front of the ears. The picture magnifies whatever is closer. At the same head size, 24 mm stands at 0.48 m, so the nose is nearly a quarter of the way closer to the lens than the ears and renders 28.6% larger. That is 19.8% larger than the nose looks at a normal talking distance.

85 mm at 1.70 m is that talking distance. The nose is only 7.3% larger than the ears, which is how a face looks across a table. 135 mm at 2.70 m is a little flatter. 50 mm at 1.00 m is already close to natural for a head-and-shoulders frame. The three pictures step closer than that table, as near as this portrait allows with the head the same size: 24 mm at 0.40 m, 50 mm at 0.83 m and 85 mm at 1.42 m.

Same head size in the portrait simulator. Person: Renderpeople

Standing still does not change perspective

Stay at 2.00 m and zoom from 24 mm to 135 mm. The person and the background grow by the same amount. It is the same picture, cropped tighter, the way a crop in software would do it. The size of the background relative to the person does not change.

Perspective changes only when your feet move. The distance from camera to person and the distance from camera to background have to change relative to each other. That is the difference between walking back and zooming.

Reference tables

Full frame. The person stays the same size as a 50 mm lens at 2.00 m, a 1.44 m wide frame at the subject. The background is 4.50 m behind the person. 24 mm is the reference.
Focal length	Horizontal angle	Camera distance	Distance to the background	Visible background width	Background scale versus the person	Background size versus 24 mm
16 mm	96.7°	0.64 m	5.14 m	11.56 m	12.5 %	0.71×
24 mm	73.7°	0.96 m	5.46 m	8.19 m	17.6 %	1.00×
35 mm	54.4°	1.40 m	5.90 m	6.07 m	23.7 %	1.35×
50 mm	39.6°	2.00 m	6.50 m	4.68 m	30.8 %	1.75×
85 mm	23.9°	3.40 m	7.90 m	3.35 m	43.0 %	2.45×
135 mm	15.2°	5.40 m	9.90 m	2.64 m	54.5 %	3.10×
200 mm	10.3°	8.00 m	12.50 m	2.25 m	64.0 %	3.64×

Full frame, a tight headshot the same size as 50 mm at 1.00 m. The nose is 12 cm in front of the ears. 85 mm at 1.70 m is the natural talking distance.
Focal length	Distance for the same head	Nose versus ears	Difference from 85 mm at 1.70 m	How the face reads
16 mm	0.32 m	+46.2 %	+36.2 %	Caricature: a huge nose, ears that fall away
24 mm	0.48 m	+28.6 %	+19.8 %	Phone or selfie look: a strong nose, a narrow face
35 mm	0.70 m	+18.8 %	+10.7 %	Fine for a half-length portrait, still a bit of nose up close
50 mm	1.00 m	+12.8 %	+5.1 %	Natural from the head to the shoulders
85 mm	1.70 m	+7.3 %	0.0 %	Classic portrait proportions
135 mm	2.70 m	+4.5 %	-2.6 %	Flattering, a slightly flatter face
200 mm	4.00 m	+3.0 %	-4.0 %	The flattest features, and you need the room

Questions

Does a telephoto lens compress space on its own?

No. Perspective depends only on where the camera stands. Telephoto compression and background compression come from stepping back so the person stays the same size. The narrower angle only crops a smaller slice of that background.

Why does a 24mm lens distort faces in close-ups?

At 0.48 m the 12 cm between nose and ears is a large share of the distance. The nose renders about 20% larger than it does at 85 mm from 1.70 m.

What focal length is most natural for portraits and headshots?

On full frame, 85 mm to 135 mm, because you stand about 1.5 m to 2.7 m away, close to a normal talking distance. On APS-C that is about 56 mm to 90 mm.

What happens if I zoom from 24mm to 135mm without moving?

The person and the background grow by the same amount. The perspective is unchanged. It is the same picture, cropped tighter.

How does background distance affect lens compression?

The farther the background sits behind the person, the more it grows relative to the person when you step back with a longer lens.