Lens Hood: What It Does, Which Shape and When to Remove It

A lens hood is a short tube or petal-shaped shade that clips onto the front of a lens and keeps light from outside the picture off the front glass. That stray light is what washes out shadows and lowers contrast, so a hood gives you richer, cleaner images when you shoot anywhere near a bright light. It also acts as a bumper for the front element and keeps rain, snow and fingers off the glass. Use the hood made for your lens, mount it facing forward, and leave it on unless you have a specific reason to take it off.

What a hood actually blocks

Every lens accepts light from a cone slightly wider than the picture it records. The light that forms the image arrives within the lens’s angle of view. Light from outside that angle, such as the sun just above the top of the frame or a streetlight off to one side, still hits the front element. It does not form part of the image, but some of it bounces between the glass surfaces and the inside of the barrel and lands on the sensor as a thin, even haze called veiling flare.

Veiling flare is easy to miss because it rarely looks like a defect. It simply lifts the darkest tones toward gray, weakens colors and makes the picture look slightly flat, as if a pale film had been laid over it. That is a loss of contrast, and it cannot be fully recovered in editing, because detail that the haze swamped in the shadows was never recorded cleanly. A hood works by putting a wall between the front element and that off-axis light. Anything outside the picture that the hood shades cannot reach the glass at all.

What a hood cannot do is stop light that comes from inside the frame. If the sun is in the picture, its light travels straight down the lens along the same paths as the rest of the scene, and no shade at the front can intercept it without also blocking part of the image. The colored ghosts, rings and streaks that follow a light source around the frame are covered in detail in the lens flare guide. The hood’s job is narrower: prevent the haze from light you did not ask for.

Why a hood’s depth depends on focal length

A hood has to be deep enough to shade the glass but not so deep that it pokes into the picture. The limit is set by the angle of view. The wider the lens sees, the wider the opening at the front of the hood must flare out, and the shorter the hood must be before its rim appears in the corners.

This is why wide-angle hoods look almost token. A 24mm lens sees so much of the world that its hood can only extend a short way before it would cut off the corners. The protection it offers is real but limited, which is one reason wide-angle lenses flare more easily when you point them anywhere near the sun. A long telephoto sees such a narrow slice that its hood can be a deep tube, blocking almost everything except the picture itself. On a fisheye, which sees 180 degrees across the diagonal, there is no room for a conventional hood at all, so the small petals are usually molded into the lens barrel.

Two consequences follow. First, a zoom lens’s hood is designed for the widest setting, because that is where it would otherwise intrude. At the long end of the zoom the hood is shallower than it could be, so a wide-to-short-telephoto zoom racked out to its longest focal length is less protected than a prime of that length with its own deeper hood. Second, the crop factor matters. A lens designed for a full-frame sensor, used on a smaller sensor, records only the center of its image circle. Its hood is sized for the wider full-frame view, so it works without vignetting but gives less shade than the narrower crop view would allow.

Petal hoods, round hoods and other shapes

The picture a camera records is a rectangle, but the front of the lens is round. A round hood has to be short enough everywhere to clear the corners of that rectangle, which are the farthest points from the center. That wastes shade along the edges, where the picture does not reach as far.

A petal hood, sometimes called a tulip hood, fixes this by following the shape of the frame. In a 3:2 frame held horizontally, the top and bottom edges are the closest to the center, so the hood has its two longest petals there. The left and right edges are farther out, so the side petals are shorter. The corners are farthest of all, so the hood is cut away almost to the barrel at the four diagonals. The result gives the most possible shade around the whole frame without any part of the hood entering the picture.

That shape only works when the hood sits in the right orientation. A petal hood mounted a quarter turn off, or one that has loosened and rotated, puts its long petals in the corners and darkens them. Bayonet hoods click into a single correct position for exactly this reason, so if yours spins freely or does not click, check it before you shoot.

• Round (cylindrical) hoods are standard on telephoto lenses, where the angle of view is so narrow that the difference between the edges and the corners is small. They are also simpler to make and tougher.
• Petal hoods suit wide and standard lenses and most general-purpose zooms, where the extra shade at the edges makes a noticeable difference.
• Built-in and sliding hoods appear on fisheyes, some compact primes and many long telephotos. The sliding type extends from the barrel when you need it and retracts for storage.
• Collapsible rubber hoods screw into the filter thread and fold back on themselves. They are less precise than a matched hood, but they are useful as a universal spare and for pressing against a window, which blocks reflections from the room behind you when you shoot through glass.

Protection from knocks, rain and fingers

Many photographers keep a hood on at all times for reasons that have nothing to do with light. A hood extends past the front element, so when a lens swings into a doorframe, a railing or a rock, the plastic rim takes the hit instead of the glass. A hood is an inexpensive, replaceable part. A cracked hood is a minor loss; a cracked front element or a bent filter thread can mean a repair.

The same projection keeps fingertips, sleeves and the edge of a bag strap off the glass. When the camera hangs from your shoulder, the front element is recessed and far less likely to pick up smudges, and a smudge scatters light in much the same way veiling flare does.

In light rain or snow, a hood keeps drops off the front element as long as the lens points level or downward. The drops land on the hood instead of the glass, which matters because a single water spot in the middle of the front element softens a whole area of the picture. Once you tilt the lens upward the hood helps much less, so between shots point it down or cover it with your hand. The practical side of working in wet weather is covered in how to photograph rain.

A hood is also the reason many people do without a protective UV filter. A filter adds two more glass surfaces in front of the lens, each of which can reflect light and add ghosts. A hood protects against the most common kinds of damage without adding any glass to the light path at all.

Wrong hoods and mechanical vignetting

A hood that is too long or too narrow for the lens darkens the corners of the frame. This is called mechanical vignetting: the hood physically blocks part of the image. It is different from the gentle optical darkening that most lenses show wide open, and it is easy to recognize because the dark corners are more sharply defined and do not fade away as you stop down. In fact, they get crisper at small apertures, because a narrower cone of light makes the edge of the obstruction more sharply outlined.

The usual causes are predictable:

• Using a hood made for a longer lens with the same filter thread size. The thread fits, but the hood is sized for a narrower view.
• A petal hood mounted out of alignment, so a long petal sits in a corner.
• A hood mounted on top of a thick filter, or a stack of filters, which pushes it forward into the picture.

To check any hood, set the lens to its widest focal length, stop down to f/16, point at an evenly lit wall or a clear sky and take a frame. Look at all four corners at full size. If any corner shows a curved dark edge, the hood is intruding. Try it with and without your filters to see whether the filter is the cause.

Mounting, reversing and storing a hood

Most modern hoods attach with a bayonet: line up the mark on the hood with the mark on the lens, push and turn until it clicks. Some older lenses use a screw-in hood instead, which blocks the filter thread while it is on.

For storage, most bayonet hoods can be reversed, fitted backward over the barrel so the lens takes almost no extra room in a bag. This is convenient, but a reversed hood covers the focus and zoom rings and gives no shade at all. Get into the habit of flipping it forward as soon as the camera comes out of the bag. It is easy to shoot a whole session with the hood reversed without noticing.

If your lens came without a hood, or you have lost it, look up the hood designed for that exact lens rather than choosing one by filter thread size. Two lenses with the same thread can have very different angles of view, and a hood that suits one may vignette on the other.

When to take the hood off

A hood is the right default, but there are specific situations where it gets in the way:

• Built-in pop-up flash. A small flash on the camera body sits only a little above the lens. At wide focal lengths the hood, and sometimes the lens barrel itself, blocks the bottom of the flash beam and casts a curved shadow across the lower part of the frame. Remove the hood, zoom in a little, or use a separate flash mounted higher. See flash photography for other ways to handle this.
• Close-up work. With a macro lens at close range, a deep hood can shade the subject from its light, block a small flash, or brush against a flower or insect and move it. Take it off when the lens is only a few centimeters from the subject.
• Rotating filters. A polarizing filter or a variable neutral density filter has to be turned to adjust it, and a deep hood makes the ring hard to reach. Some hoods have a small sliding window for this purpose. Otherwise, set the filter first and fit the hood afterward if your hood allows it, or accept a slightly shallower hood for that session.
• Strong wind on a tripod. A long hood on a telephoto acts a little like a sail. In gusty wind it can add vibration, so remove it if you see softness that comes and goes with the gusts.
• Deliberate flare. If you want a wash of warm haze from a low sun, the hood is working against you. Take it off on purpose, as described in backlighting.

Improvising a hood

When the hood is at home, in the bag or simply not deep enough, you can shade the lens with whatever you have. The principle is the same: put something opaque between the front element and the light source, as close to the lens as possible without entering the frame.

• Your hand. Hold it above or to the side of the lens so its shadow falls across the front element. Watch the screen: the haze clears the moment the glass goes into shade.
• A hat brim, a notebook or a map. Larger objects shade longer lenses and do not need a steady hand on a tripod.
• A rolled sheet of dark card. Wrapped around the front of the lens and held with a rubber band, it makes a serviceable round hood. Trim it back until the corners of the frame are clean.
• Something in the scene. A tree trunk, a building or a friend standing out of shot can block the sun from reaching the lens.

Common mistakes

• Shooting with the hood reversed. It gives no shade and blocks the rings. Flip it forward every time you take the camera out.
• Using the hood only on sunny days. Veiling flare comes from any bright source outside the frame, including an overcast sky above the horizon, stage lights and streetlights. Leave it on by default.
• Buying a hood by thread size alone. The thread fits many lenses, but the depth is designed for one angle of view. Match the hood to the exact lens, then test the corners.
• Ignoring a rotated petal hood. If the corners suddenly go dark, check whether the hood has twisted out of its click position.
• Expecting the hood to stop flare from a light inside the frame. It cannot. Reposition, hide the light behind something, or embrace it.
• Leaving it on with the pop-up flash. The semicircular shadow at the bottom of the frame is the hood. Remove it for flash at wide focal lengths.
• Stacking filters under the hood on a wide lens. The extra thickness pushes the hood into the frame. Use one thin filter or none.

Try this

This takes about 15 minutes on a bright day or at night near a streetlight. Set the camera on a tripod or a steady surface and frame a scene with plenty of dark tones, such as shaded foliage, a doorway or a dark building, with a bright light source just outside one edge of the frame. Do not include the light itself.

1. Take one frame with no hood.
2. Take one frame with the hood mounted correctly.
3. Take one frame with the hood reversed, as it would be if you forgot to flip it.
4. Take one frame with the hood on and your hand shading the lens from the light as well.
5. Set your lens to its widest focal length and f/16, point at a plain sky or wall, and take one frame with the hood and one without, to check for vignetting.

Compare the first four frames side by side at the same exposure. Look at the darkest area in each: the difference in how black the shadows stay is exactly what the hood is doing for you. Check the last pair for dark corners. You will come away knowing how much protection your particular lens and hood give, and whether they ever get in the way.

Frequently asked questions

Should I leave my lens hood on all the time?

For most shooting, yes. It improves contrast whenever there is a bright light outside the frame and protects the front element from knocks and smudges. Remove it for pop-up flash at wide angles, close macro work, and when you want flare on purpose.

Does a lens hood reduce image quality?

No. A hood contains no glass, so it adds nothing to the light path. The only way it can harm a picture is by darkening the corners if it is the wrong hood or is mounted incorrectly.

Is a lens hood useful at night?

Yes. Streetlights, car headlights and lit signs just outside the frame cause the same veiling haze as the sun, and at night it is especially visible because it lifts the dark areas that make a night scene look rich.

Why is my wide-angle hood so short?

Because a wide lens sees so much of the scene that any longer hood would appear in the corners of the picture. The short hood gives as much shade as the angle of view allows.

Related guides

• Lens flare: ghosts, veiling flare and starbursts, and how to prevent or use them.
• Contrast: what veiling flare takes away and why it matters.
• Angle of view: the geometry that decides how deep a hood can be.
• Vignetting: the difference between optical and mechanical corner darkening.
• Polarizing filter: the filter most often awkward to use with a hood.
• UV filter: whether a protective filter is worth adding in front of the lens.
• Backlighting: shooting toward the light, where a hood matters most.
• Star-shaped lens flare: a light effect that happens inside the frame, where a hood has no influence.