Speedlight / Speedlite

A speedlight is a small, battery-powered flash that slides into your camera’s hot shoe or fires from somewhere else on a wireless signal. It matters because it is one of the cheapest, lightest ways to make your own light: one in a bag lets you light a face in a dark room, fill the shadows of a sunny afternoon, or freeze a splash, wherever you are.

This page is about the device itself: what is inside it, what each control does, what its numbers mean, and what it can and cannot do compared with a studio light. How to use flash in a picture, from choosing the mix of flash and daylight to setting exposure, is on flash photography.

Speedlight or Speedlite: two spellings, one device

“Speedlight” is the general name. “Speedlite” is one camera maker’s trademarked spelling of the same thing, and other makers use their own names, so you will also see “hot shoe flash”, “flashgun” and “accessory flash”. They all mean a self-contained flash small enough to sit on the camera, with a head you can point.

It is not the same as the pop-up flash built into some cameras. A pop-up flash is weaker, fixed in place a few centimeters above the lens, and always points straight ahead. A speedlight has several times the power, sits higher, and its head turns, which is what lets you bounce it. It is also not a studio strobe, which is a larger, more powerful flash usually run from the mains; more on that below.

What happens inside when it fires

The batteries cannot deliver a big burst of energy all at once, so the flash stores it first. A circuit steps the battery voltage up to a few hundred volts and fills a capacitor; that is the whine you hear after switching it on. When the camera opens the shutter, it signals the flash through the pins on the foot, and the capacitor dumps its charge through a glass tube filled with xenon gas. The gas glows white for a tiny fraction of a second.

Three parts of the head then shape that burst:

• The reflector behind the tube throws the light forward.
• The Fresnel lens on the front, a flat sheet of plastic with ridges, spreads or concentrates the beam. The window is small and rectangular, which is why bare speedlight light is hard and makes crisp shadows.
• The zoom motor slides the tube and reflector closer to or farther from the lens, which widens or narrows the beam (see the zoom head below).

The light is close to daylight in color, roughly 5,500 K, so it mixes well with the sun and badly with warm indoor bulbs unless you add a gel. If color temperature is new to you, that page explains the numbers.

Power: guide numbers and the fractions on the screen

A speedlight’s power is given as a guide number (GN): the subject distance multiplied by the f-number that gives a correct exposure at full power. A flash with GN 40 (meters, ISO 100) exposes a subject 10 meters away correctly at f/4, because 10 × 4 = 40, or a subject 5 meters away at f/8. Full-size speedlights usually quote somewhere around GN 30 to 60 in meters at ISO 100. Two catches: the number only compares fairly at the same ISO and the same zoom setting, and makers usually quote it at the longest zoom, where the beam is narrowest and the number looks biggest.

In manual mode you set power as a fraction of full: 1/1, 1/2, 1/4 and down to 1/128, and on many flashes 1/256. Each halving is exactly one stop less light, and most flashes also offer thirds of a stop between. Because light falls with the square of distance (the inverse square law), one stop less light covers about 1.4 times less distance. Here is what that means for a GN 40 flash with the subject lit directly at f/4 and ISO 100:

Read the table the other way and it says something useful: a person 2.5 meters from a direct flash needs only 1/16 power at f/4 and ISO 100. Most of the time a speedlight works far below full power, which is good, because lower power means faster recycling, less heat and a shorter burst. Raise the ISO one stop and every distance in the table grows by about 1.4 times. Bouncing or a modifier eats light, often two to four stops or more, which is when the top rows start to matter.

Want the aperture for your own flash, ISO and distance without doing the arithmetic? The flash guide number calculator works it out.

The zoom head: aiming the same light wider or tighter

The zoom setting on a speedlight is a number in millimeters, typically 24 to about 105 or 200, meant to match the focal length of the lens. Left on auto, the flash reads the lens and follows it. The beam’s shape follows the setting: wide spreads the light across the whole frame, long squeezes it into the middle.

That gives you three uses beyond simple matching:

• Reach. Zooming the head tighter puts more of the same burst on a distant subject, which is why the guide number rises with the zoom setting.
• A spotlight. Zoom to the longest setting while shooting wide and you get a bright pool on the subject with darker edges, a quick vignette with no modifier.
• Control when bouncing. A tight zoom aimed at the ceiling makes a small bounce patch; a wide zoom makes a bigger, softer one that also leaks light around the room.

For very wide lenses, most speedlights have a pull-out wide panel that spreads the beam further, and many also have a small white bounce card that tucks behind it. The panel costs light; the card throws a little light forward to put a catchlight in the eyes when the head points up.

Recycle time, batteries and heat

After each burst the capacitor has to refill. That wait is the recycle time, and makers quote it at full power, usually somewhere from about 1.5 to 5 seconds on fresh AA cells. Since a half-power burst uses half the charge, it refills in roughly half the time, and at 1/16 or below the flash is ready again almost at once. If you are missing moments because the flash is not ready, turn the power down and the ISO or aperture up rather than buying a stronger flash.

• Batteries. Most speedlights take four AA cells. Rechargeable nickel metal hydride cells usually recycle faster than alkalines and hold up better through a long shoot. Some flashes use a lithium-ion pack instead, which keeps recycle times short until it is nearly empty. External battery packs plug into many speedlights for event work. More on keeping power ready in camera batteries.
• Heat. The flash tube and head get hot. Fire a string of full-power bursts quickly and the flash will slow itself down or stop to protect itself, and pushing past that can damage the head. Lower power, rest between bursts, or spread the work across two flashes.
• The ready light. Fire again before the capacitor has refilled and the flash either skips the frame or, on some units, gives a weaker burst. If one frame in a fast sequence is dark, that is usually why.

TTL or manual: who decides how bright the burst is

In TTL mode (through the lens) the flash fires a weak pre-flash a moment before the real one. The camera measures what comes back through the lens with its metering system and tells the flash how much power to use. It is quick when the distance to your subject keeps changing, at a party or a wedding reception for example. It can also be fooled, like any meter, by a white dress or a dark suit, and you correct it with flash exposure compensation on the flash or the camera.

In manual mode you set the fraction yourself and the flash gives exactly that every time. It is the better choice whenever the light and subject stay put: a portrait setup, a product on a table, a flash on a stand. Neither mode is better in general. Many photographers use TTL on the camera at events and manual whenever the flash is on a stand. Flash photography walks through choosing and correcting each.

Most speedlights also have a few extra modes: a multi or stroboscopic mode that fires several small bursts during one exposure, and on older or simpler units an “auto” mode that reads the light with a sensor on the flash itself instead of through the lens.

What the shutter decides and what the flash decides

A speedlight burst is short: at low power often shorter than 1/10,000 second, at full power much longer, often somewhere around 1/1,000 second or slower. That is why flash freezes motion, and why lowering the power freezes it better; flash duration explains how to use it. Because the burst is so short, the shutter speed hardly changes how bright the flash looks. It changes how bright the room or the sky looks behind it.

The shutter does set a limit. Above the camera’s flash sync speed, often around 1/200 or 1/250 second, the shutter never fully opens at once and a normal burst lights only part of the frame. Speedlights get around this with high-speed sync, which pulses the light through the whole exposure at a heavy cost in power. You can also choose when in the exposure the flash fires: front curtain sync fires at the start, rear curtain sync at the end, which puts motion trails behind a moving subject instead of in front of it.

Three places to put it: on the camera, bounced, or off the camera

Where the flash sits matters more than how powerful it is.

• On the camera, pointed straight ahead. The light comes from beside the lens and from a small window, so it is flat and hard: shiny skin, few shadows on the face, a hard shadow on the wall behind. Useful for fill outdoors (see fill flash) and when nothing else works.
• On the camera, bounced. Tilt or swivel the head toward a white ceiling or wall and the wall becomes the light: big, soft and coming from a direction you chose. Bounce flash covers where to aim and how much power it costs. This is the biggest single reason a speedlight beats a pop-up flash.
• Off the camera. On a stand or in someone’s hand, fired by radio or by a commander flash on the camera, the speedlight becomes a small studio light you can put anywhere. Off-camera flash covers the first setups, and flash triggers compares radio, optical and cable.

The falloff tool below shows why position matters so much: drag the light and the wall and watch how fast the flash light drops with distance, and how the background goes dark when the flash is close to the subject.

Background going black every time you use flash indoors? Balancing flash and ambient light explains how the shutter speed brings the room back.

Shaping a speedlight’s light

Bare, a speedlight is a small source and makes hard light. To soften it you make the source bigger relative to the subject: bounce it, or fire it into or through a modifier. Small softboxes, shoot-through and reflective umbrellas, and small beauty dishes all work, mounted with a bracket that holds the flash on a stand. To narrow it, a snoot makes a small spot and a grid keeps the beam from spilling. A light modifier page compares the families, and hard vs soft light explains why size and distance decide softness.

Keep the power budget in mind. A large softbox or umbrella can cost a speedlight two or three stops or more, and a speedlight was never very strong to begin with. That is where the comparison with studio lights starts.

Speedlight or studio strobe

A speedlight and a studio strobe make the same kind of light. The differences are power, convenience and price.

• Power: Speedlight: Modest; enough for most single portraits close to a modifier. Studio strobe: Several times more; enough for big modifiers, groups, or small apertures in sun.
• Power source: Speedlight: AA cells or a small pack. Studio strobe: Mains, or a large battery on location models.
• Recycle at full power: Speedlight: A few seconds. Studio strobe: Usually faster.
• Modeling lamp: Speedlight: Usually none, so you judge by test shots. Studio strobe: Usually a continuous lamp to preview the light.
• Modifiers: Speedlight: Small ones, held on a bracket. Studio strobe: Mounts for large softboxes and dishes.
• Size: Speedlight: Fits a coat pocket; three in a small bag. Studio strobe: Needs its own case and stands.

For people, small products and anything on location, speedlights are often all you need, and several of them together can do what one big light does. Joe McNally built much of his teaching around exactly that idea, lighting large scenes with small hot shoe flashes. Photographers who have outgrown speedlights usually did so for power, recycle time or a modeling lamp, not for better light. Studio lighting setup covers the bigger kit, and continuous lighting is the other option when you want to see the light before you shoot.

Ready to put two or three flashes together? Lighting setup diagrams show where each light goes in the classic portrait patterns.

Common mistakes with speedlights

• Pointing it straight at the subject by habit. Direct on-camera flash is the flattest light you can make. Look up first: a white ceiling or wall nearby is a free softbox.
• Judging a flash by its guide number alone. Numbers quoted at different zoom settings or in feet against meters are not comparable, and a flash you run at half power on most shots barely needs a higher number. Recycle time, controls and how it triggers off camera matter as much.
• Running at full power when you do not need to. It slows recycling, heats the head and lengthens the burst. Open the aperture or raise the ISO a stop and drop the flash a stop.
• Letting the zoom follow the lens when bouncing. With a normal or long lens, auto zoom aims a tight beam at a small patch of ceiling. Set the zoom wider for a bigger, softer bounce.
• Firing before it has recharged. A dark frame in a sequence is usually a flash that was not ready. Watch the ready light, or work at lower power.
• Putting an old flash on a new camera. Some older flashes put a high trigger voltage across the hot shoe, which can damage some digital cameras. Check the flash’s trigger voltage, or fire it through a radio trigger instead.
• Forgetting the color of the room. Daylight-colored flash against warm bulbs gives a white face on an orange background. A warming gel on the flash and a matching white balance fix it.

Try this: learn your flash’s power ladder in ten minutes

You need the speedlight, your camera and a willing person or an object about the size of a head, in a room with a white ceiling.

1. Set the camera to manual: ISO 100, f/4, 1/125 second. Put the flash on the camera in manual mode, head pointed straight ahead, zoom at 50mm.
2. Stand 2.5 meters from your subject. Shoot at 1/1, 1/4, 1/16 and 1/64 power. If your flash’s guide number at the 50mm zoom setting is around 40 (its manual lists the number for each zoom setting), the 1/16 frame should be close to right; the others will be about two stops apart from each other.
3. Now tilt the head to point at the ceiling, zoom at 24mm, and repeat at 1/4 and 1/1.
4. Last, zoom the head to its longest setting, point it straight ahead again at the right power, and shoot with the lens zoomed out wide.

Judge the results on the camera’s histogram and by eye. The direct frames should step down by about two stops each. Find the frame where the face looks right and note its power: that is your flash’s real strength at that distance. The bounced frames should need several stops more power and show softer shadows under the nose and chin. The last frame should show a bright pool in the middle and dark corners. If your exposures do not move as expected, check that the flash is in manual mode and fully recharged between shots.

Speedlight questions people ask

Is a speedlight worth it if my camera has a pop-up flash?

Yes, if you want to use flash for more than emergencies. The head that tilts and swivels is the big difference: it lets you bounce the light off a ceiling or wall so it becomes soft and comes from the side. A speedlight also has several times the power and can be taken off the camera.

Will any speedlight work on my camera?

Almost any flash will fire from the center pin of a standard hot shoe in manual mode. TTL, high-speed sync and control from the camera menu need a flash that speaks your camera’s protocol. With very old flashes, check the trigger voltage first, or fire them through a radio trigger.

How many speedlights do I need?

One, used bounced or off the camera, will teach you most of what flash can do. A second adds a rim or background light, and a third is usually for a background or a hair light. Learn to use one well before adding more.

Can a speedlight freeze motion?

Yes, and at low power it does it very well, because the burst gets shorter as the power drops. In a dim room the flash, not the shutter, sets how sharp a moving subject is. In bright daylight the ambient light also records, so motion can blur anyway.

Why are my flash photos orange or blue in places?

The flash is close to daylight in color, and most indoor bulbs are much warmer. The parts of the frame lit by the flash come out neutral and the parts lit by the room come out orange. Put a warming gel on the flash and set the white balance for the room lights.

Should I use rechargeable batteries in a speedlight?

Usually yes. Rechargeable nickel metal hydride AA cells generally recycle faster than alkalines and keep doing so for longer through a shoot. Carry a spare set, since a flash’s last few bursts on tired cells come slowly.

Want to see how much of this has stuck? The flash photography quiz asks about speedlights, TTL and sync speed.