Understanding Lens Distortion: Barrel, Pincushion, and Perspective

Lens distortion is what happens when a lens records straight lines in the scene as curved lines in the photo: a doorframe near the edge of the frame bows outward, or a horizon dips at both ends. It matters because it changes the shape of things without making the picture any less sharp, so it slips past you until you photograph a building, a room or a ruler-straight horizon, and then it is all you can see.

The word gets used for much more than that. Big noses in close-up portraits, buildings that lean backward, and stretched faces at the edge of a group shot are all called “distortion”, yet each has a different cause and a different fix, and a lens profile in your editor repairs only one of them. This page explains true lens distortion first, then sorts out the look-alikes so that you can name the cause of any odd-looking frame and reach for the fix that actually works.

What lens distortion is: magnification that changes from center to edge

An ideal ordinary lens is rectilinear: every straight line in the scene stays straight in the picture. A real lens gets close, but its magnification usually changes a little with distance from the center of the frame. If the image is magnified slightly less toward the edges, everything out there is pulled toward the center and straight lines bow outward. If it is magnified slightly more, they bow inward.

Two consequences follow from that one idea, and they are the quickest way to recognize lens distortion in a photo:

• Lines that pass through the center stay straight. Only lines that run off-center curve, and the farther from the center they run, the more they curve. Put a horizon through the middle of the frame and it stays flat; put it near the top and it bends.
• Shape changes, sharpness does not. Distortion moves detail to the wrong place. It does not blur it, fringe it or darken it. Soft corners, color fringes and dark corners are different faults: chromatic aberration and vignetting have pages of their own.

Barrel distortion

Barrel distortion bows straight lines outward, as if the picture were printed on the side of a barrel. It is the common kind in wide-angle lenses and in zoom lenses at their shortest focal length. It gives a wall of tiles a slightly puffed-out look and makes horizons near the top or bottom of the frame sag or hump.

Pincushion distortion

Pincushion distortion bows lines inward, so the middle of each edge looks pinched toward the center and the corners look pulled out. It is typical of telephoto lenses and of zooms at their longest setting. It is often less noticeable than barrel because long-lens pictures tend to have fewer straight lines near the edges, but a window frame or a fence at 200 mm can show it.

Mustache distortion

Mustache (or wavy) distortion is a mix: barrel near the center turning into pincushion toward the edges, so a straight line near the top of the frame rises, dips and flicks up again like a handlebar mustache. It shows up in some compact wide-angle designs. It is the awkward one, because a single distortion slider pushes the whole frame one way and cannot straighten a line that bends both ways.

Why lenses distort, and what does not change it

Distortion is a design trade-off, not a fault of wide angles as such. It comes mostly from how lopsided the lens design is around its aperture. Lens designs that are close to symmetrical front to back can be almost free of it, even at wide angles. Most wide-angle lenses for interchangeable-lens cameras, and almost all zooms, are strongly asymmetrical so that they sit far enough from the sensor and stay a sensible size, and they distort more. A typical zoom shows barrel at the wide end, pincushion at the long end, and a nearly clean point somewhere in between. Prime lenses are not automatically free of it: plenty of wide primes show visible barrel.

Some things do not change it at all. Stopping down does not reduce distortion: the lines are just as bent at f/11 as at f/2.8. What stopping down changes is sharpness and vignetting. Distortion is set by the lens design, the focal length on a zoom, and to a lesser degree the focus distance.

Lens reviews often give distortion as a percentage, measured from a test chart: the number says how far the edge of the picture is pulled in or pushed out compared with a perfect rectilinear image. By the usual convention a negative figure means barrel and a positive one pincushion. As a rough guide, about 1 percent or less is hard to see outside architecture and product shots, while 3 percent or more bends a straight horizon visibly. Different test methods report numbers on different scales, so compare figures only within one source.

Which distortion is it? Five causes and their fixes

Most pictures people describe as “distorted” have nothing wrong with the lens. Look at the lines and shapes in the frame and match the symptom here before you reach for any fix.

• Straight lines curve, more so near the edges; lines through the center stay straight: What causes it: Lens distortion (barrel, pincushion, mustache). Does a lens profile fix it? Yes. What fixes it: Lens profile or distortion slider.
• Almost every line curves strongly, often in a round picture: What causes it: A fisheye lens, a different projection chosen on purpose. Does a lens profile fix it? No; it is the lens doing its job. What fixes it: A defish or projection change, at a large crop.
• Lines stay straight but lean together (a building tapering toward the sky): What causes it: Camera tilted up or down: converging verticals. Does a lens profile fix it? No. What fixes it: Hold the camera level, step back, use a shift lens, or a transform tool.
• Lines stay straight but round things near the edges look stretched (wide faces, oval wheels): What causes it: Rectilinear projection at a wide angle. Does a lens profile fix it? No, and correcting barrel makes it slightly worse. What fixes it: Keep people away from the edges, use a longer lens, or a cylindrical or similar projection.
• Near things look huge and far things tiny (big nose, small ears); or the reverse, a background that looks stacked close behind the subject: What causes it: Camera-to-subject distance: perspective. Does a lens profile fix it? No. What fixes it: Change where you stand, then choose the focal length that frames it.

Only the first row is lens distortion in the strict sense. The rest are about geometry and where you put the camera, and the sections below take them one at a time.

Fisheye: curved lines on purpose

A fisheye lens is not a badly corrected wide-angle. It uses a different projection, one that squeezes a huge angle of view (often 180 degrees across the diagonal or the whole circle) into the frame by letting straight lines curve. A rectilinear lens cannot do that: as its angle of view approaches 180 degrees, the edges would have to stretch without limit. So a fisheye bends lines instead, and, like ordinary distortion, a line that passes through the center of the picture stays straight.

You can “defish” a fisheye picture in software into a rectilinear one, but you lose a lot of the frame and the edges stretch heavily, which is the price of the wide view. Most people who use a fisheye want the curve: it suits skateboarding, tight interiors, and pictures where a curved horizon or a bulging subject is the point. Keep the horizon through the center if you want it straight. The fisheye lens page covers circular and full-frame types and what each sees.

Stretched edges: the wide-angle effect a lens profile cannot fix

Here is the one most often blamed on the lens. In a wide-angle group photo, the people at the ends look wider and their heads look oval, even though the walls and door frames behind them are perfectly straight. That is not barrel distortion. It is what a perfect rectilinear lens does. To keep straight lines straight on a flat sensor, it has to spread anything at a steep angle off the center across more of the frame, and a round object out there comes out longer in the direction pointing away from the center.

The stretch is easy to compute. For a small round object, its length along the line from the center divided by its width across it is 1 divided by the cosine of the angle between it and the lens axis. The corners of a full frame sensor are 21.6 mm from its center (half of the 43.3 mm diagonal), so the angle at a corner is the arctangent of 21.6 divided by the focal length:

On a smaller sensor, use the full frame equivalent focal length: a 16 mm lens on an APS-C camera with a 1.5x crop behaves like the 24 mm row. So a face in the corner of a 24 mm frame is about a third wider than it should be, and in the corner of a 14 mm frame close to twice as wide. At 50 mm it barely registers.

Two things follow. First, applying a lens profile does nothing for stretched faces; removing barrel distortion actually pushes the edges outward and stretches them a little more, because mild barrel was partly counteracting the effect. Second, the effect depends on viewing distance. A wide picture looks natural when you view it from the distance at which it covers the same angle your lens did: the focal length times the enlargement. A 14 mm frame printed 36 cm wide is enlarged 10 times, so it looks right from 14 cm away, which nobody does. Seen from across a room, the edges look stretched. A 50 mm frame at the same size looks right from 50 cm, about where you would hold it.

The practical fixes: keep faces and round objects away from the edges and corners of a wide frame, step back and use a longer focal length when people matter, and for wide group shots or tall interiors use your editor’s cylindrical or similar projection (some editors call the face fix “volume” or “perspective” correction), which trades a little line curvature for rounder heads.

Lining up a big group? How to photograph groups covers lens choice and where to put people so nobody ends up at the stretched edge.

Perspective distortion: set by where you stand

Perspective distortion is the change in relative size between near and far things, and it depends only on where the camera is. Photograph a face from 30 cm and the nose, about 12 cm closer to you than the ears, is recorded about 1.4 times larger relative to them than it would be from far away. The lens has nothing to do with it; distance does. The table assumes head-and-shoulders framing on full frame (about 50 cm of subject across the long side of the frame) and shows the lens you would need at each distance to get that framing:

That is why portrait photographers favor 85 to 135 mm on full frame (about 55 to 90 mm on APS-C): those lenses fill the frame with a head and shoulders from about 1.3 to 2 m away, where the face keeps its usual proportions. A wide lens used from close up gives the big-nose look; the same wide lens used from 2 m gives a normal-looking face, small in a big frame. Crop that frame down to head and shoulders and you get exactly the proportions of a 135 mm shot taken from the same spot, just with fewer pixels.

The same rule runs in reverse at a distance. A long lens seems to “compress” a scene, with a mountain stacked right behind a nearby building, because you had to stand far back to frame them, and from far back the two are similar in distance from you. Getting close with a wide lens stretches space instead: a rock 50 cm from the lens towers over hills a kilometer away. Neither can be fixed in software, because how much things should grow or shrink depends on how far away each one is, which a flat photo does not record.

The lens compression page has an interactive tool that lets you move a camera back and forth and change the focal length, so you can watch the background grow or shrink while the subject stays the same size.

The same tool is here. Choose Keep the person the same size, change the focal length, and watch the fence, trees and mountains behind the person grow or shrink while the person stays put; then choose Stand still and see that zooming alone only crops.

Want the whole idea of perspective, not just faces? Perspective distortion covers extension, compression and how to use each.

Converging verticals: the camera is tilted

Point a camera up at a tall building and its sides lean toward each other, as if it were falling backward. This is often called keystone distortion, and it is not caused by the lens at all: any lens does it, because the sensor is no longer parallel to the face of the building, so the top of the building is farther away and comes out smaller. Point the camera down from a high window and the verticals converge toward the bottom of the frame instead. Barrel distortion bends lines; tilt keeps them straight and makes them lean.

Fixes, in order of how much picture they keep: hold the camera level (use the level in the viewfinder) and step back or crop away the empty foreground; use a shift lens, which slides the lens up so the top of the building fits while the sensor stays parallel to it; or straighten the lines afterward with your editor’s perspective transform, which crops the frame and stretches the top, so leave room around the building when you shoot. Correcting verticals fully can make a tall building look top-heavy; many architectural photographers leave a slight lean in.

Verticals leaning because you tilted the camera up? The Transform tool walks through straightening them step by step.

Correcting lens distortion in software

Real lens distortion, the first row of the table, is the easy one to fix, because for a given lens and focal length it is the same in every picture.

• Lens profiles. Most editors, and many phone and camera apps, hold correction profiles for thousands of lenses. Turn on profile correction and the editor reads the lens and focal length from the file’s EXIF data and undoes that lens’s measured distortion, mustache included. This is the most accurate method and the one to try first.
• A distortion slider. If there is no profile for your lens, an adapted old lens for example, drag the distortion slider while watching a straight line near the edge of the frame, with a grid overlay on. This works well for simple barrel or pincushion and poorly for mustache.
• In-camera correction. Many cameras correct distortion in JPEGs automatically, and many lenses for mirrorless cameras are designed to rely on it, which keeps them small. In raw files the correction is often stored as an instruction that the editor applies, sometimes without an option to turn it off.

Correction is not free. Straightening barrel stretches the edges outward, so the corners are cropped away and the edges lose a little resolution. Correct lens distortion before you straighten perspective, because the transform needs straight lines to work from, and leave a little room around the edges when you shoot anything that will need both.

Not every picture needs it. A landscape of trees and rocks has no straight lines to betray mild barrel, and correction only costs pixels. Correct when a straight line in the picture looks wrong.

Want the full set of fixes, including vignetting and color fringes, in the order an editor applies them? Lens corrections covers each panel.

Using distortion on purpose

Each of these effects can serve a picture. Going close with a wide lens makes a foreground flower or rock dominate the frame and pulls the viewer in, which is why landscape photographers put strong shapes a step from the lens. In street photography, working close with a 28 or 35 mm lens gives the feeling of standing in the scene. A long lens from far away stacks hills, streets and crowds into flat layers. A fisheye curve makes a skate ramp or a small room feel enormous. Converging verticals, pushed hard from the foot of a tower, make it soar. More on working close is on the wide-angle lens page. The only rule is to make the choice deliberately: lean all the way in, or keep the lines straight.

Common mistakes with lens distortion

• Blaming the lens for stretched faces. Edge stretching comes from rectilinear projection and close distances, not from barrel distortion. A lens profile will not round a stretched head; moving the person toward the center, or stepping back with a longer lens, will.
• Calling a leaning building barrel distortion. If the lines are straight but converge, the camera was tilted. A distortion slider will just bend them.
• Thinking wide lenses “distort faces”. Distance does that. A wide lens only tempts you to stand too close to fill the frame.
• Stopping down to reduce distortion. Aperture has no effect on how straight lines bend. Choose a different focal length on a zoom, or correct it afterward.
• Assuming a prime is distortion-free. Many wide primes show plain barrel. Test yours on a straight line.
• Judging a lens with in-camera correction switched on. A JPEG you think shows no distortion may have been corrected already. Check the camera’s lens correction setting, or look at the raw file in an editor with correction off, before deciding about a lens.
• Leaving it uncorrected where lines matter. In real estate and architecture pictures, bowed door frames and leaning walls read as careless. Correct the lens, then the verticals, every time.
• Putting the horizon at the top of a wide frame. Barrel bends it into a dome. If you can, keep straight horizons near the middle, then crop.

Try this: a ten-minute distortion hunt

You need a flat wall with straight lines (tiles, bricks, a bookcase or a window grid), a zoom lens or a phone with more than one camera, and a friend or a ball.

1. Turn off in-camera distortion correction if your camera has the setting, or shoot raw. Stand square to the wall, camera level, so the wall fills the frame.
2. Take one frame at your widest setting with a line of the wall running along the top edge of the frame, and a second frame with that line through the center. Repeat at your longest setting.
3. Without moving your feet, tilt the camera up so the wall’s verticals lean. Take one frame.
4. Put your friend’s face or the ball in a corner of the widest frame, then in the center. Take both.
5. Last, at the widest setting, take a head-and-shoulders frame from close up, then step back until a long setting gives the same framing, and take another.

How to judge it. Lay a ruler on the screen. The line along the top edge at the wide end should bow (barrel if it humps outward), at the long end it may pinch inward (pincushion), and the same line through the center should be straight; if both are straight, your lens is well corrected or the correction is baked in. Now turn on the lens profile in your editor: the curve should vanish, while the leaning verticals, the oval face in the corner and the big nose in the close frame stay as they were (the corner face even gets a touch longer). If you can name which of the five causes produced each of those, you have it.

Want to measure more than distortion while you are at it? How to test a lens checks sharpness, decentering and focus accuracy with a flat target.

Want to check you can tell barrel, pincushion and perspective distortion apart? Try the lens distortion quiz.

Lens distortion questions

Is lens distortion a sign of a bad lens?

No. Most lenses have some, and many good modern lenses are deliberately designed with more of it because software removes it cleanly and the lens can be smaller. What matters is whether it is corrected, either by a profile or by the camera, before you look at the picture.

Does a phone camera have lens distortion?

Yes, especially the ultra-wide camera, but the phone corrects it before you see the picture. What you still see in phone ultra-wide shots is edge stretching from the wide projection, which is why people at the ends of a group selfie look wider. Some phones add a separate face correction for that.

Why do the stretched edges of a wide-angle photo look normal when I put my eye close to it?

Viewing distance. A wide frame looks natural only from the focal length times the enlargement, which for a 14 mm frame printed 36 cm wide is 14 cm. Bring your eye that close, so the picture fills as much of your view as the scene filled the lens, and the edge stretch fades; step back and it returns.

Which focal length has no distortion?

None is guaranteed. On many zooms the cleanest point is somewhere in the middle of the range (on a standard zoom for full frame, often around 35 to 50 mm), and longer primes usually show very little. Test your own lens on a straight line, with correction off, to find out.

Can I fix a big nose from a close-up portrait in software?

Not properly. The nose is too big because it was closer than the rest of the face, and the photo does not record how much closer, so no lens profile can undo it. Some editors and phone apps can warp faces to make it less obvious, but the real fix is to step back and use a longer focal length.