Strobes and continuous lights

Studio lights fall into two families: flash, also called strobe, which produces a very brief, intense burst of light, and continuous light, which stays on. Each has strengths, and many studios use both. Choosing between them affects how you work, what subjects you can photograph, how much power you have, and whether you can also shoot video. This lesson covers the types of flash, from speedlights to monolights and pack-and-head systems; continuous lights including LED, tungsten and fluorescent; colour quality; power and output specifications; modelling lights; battery and mains power; and how to choose a starter kit.

Why flash dominates stills studios

Flash concentrates its energy into a burst lasting from about 1/300 to 1/10,000 of a second or less. This makes it far brighter than any practical continuous light of similar size and power consumption: a modest 400 watt-second studio flash, firing through a large softbox, can light a portrait at f/8 or f/11 at ISO 100, while a continuous light would need to be many times more powerful to achieve the same exposure at a hand-holdable shutter speed. Flash freezes motion, including blinking, hair movement and small movements of the subject, and its short duration means that the camera's shutter speed has little effect on the flash exposure (Lesson 3). It runs cool, because the light is on only briefly, and it does not dazzle subjects for long. Its disadvantages are that you cannot see the exact effect of the flash until you take a picture, which is why studio flashes have modelling lights; that shutter speeds are limited by flash sync; and that flash cannot be used for video.

Speedlights

Speedlights, also called hot-shoe flashes or speedlites, are small, battery-powered flashes that mount on the camera or on a stand. They produce about 50 to 80 watt-seconds of energy, are portable and inexpensive, offer automatic TTL exposure and high-speed sync with compatible cameras, and can be triggered wirelessly. Their small, hard light needs modification with umbrellas or small softboxes for most portraits, and their limited power and slower recycling at full power restrict them in large studios or with large modifiers. Many photographers start with two or three speedlights, which also serve on location. They are often called small flash, and a whole approach to lighting, popularized by photographers such as David Hobby's Strobist website, grew around them.

Monolights and battery strobes

Monolights are self-contained studio flashes with the power supply, capacitors, flash tube and modelling light in one head, connected to mains power or to a battery. Typical outputs range from about 200 to 1,000 watt-seconds. They mount on stands, accept a wide range of modifiers through a standard mount such as the Bowens S-type, Profoto or Elinchrom mounts, and offer adjustable power over five to ten stops, wireless control and fast recycling. Battery-powered monolights and compact strobes, from manufacturers such as Godox, Profoto, Elinchrom and Broncolor, have transformed location work, providing studio power without cables. For most small and medium studios, two to four monolights form the core of the lighting kit.

Pack-and-head systems

Pack-and-head systems separate the power pack, containing capacitors and controls, from the flash heads, connected by cables. One pack can power several heads, distributing power between them symmetrically or asymmetrically, and packs can deliver very high power, from 1,200 to 3,200 watt-seconds or more. Heads are lighter than monolights, which helps on booms and high stands, and some systems offer extremely short flash durations for freezing fast action. Pack systems are used in large commercial studios, fashion and car photography and wherever high power is needed. They are more expensive and less flexible for small studios.

Watt-seconds and actual output

Flash power is usually quoted in watt-seconds (Ws) or joules, which measure the electrical energy stored in the capacitors, not the light produced. Two flashes with the same watt-second rating can differ in light output by a stop or more because of differences in flash tube efficiency, reflector design and the modifier used. Comparing flashes by the exposure they produce at a set distance with a standard reflector, sometimes given as a guide number or as an f-stop at 2 m and ISO 100, is more useful. Each doubling of watt-seconds gives one stop more light, so a 400 Ws flash is one stop more powerful than a 200 Ws flash of similar design, and a 1,600 Ws pack is two stops more than a 400 Ws monolight.

Modelling lights

Because flash fires too briefly to see, studio flashes include a continuous modelling light, traditionally a tungsten halogen bulb and now usually an LED, positioned near the flash tube. It shows approximately where the light falls, the shape of shadows and the position of catchlights. Many flashes can set the modelling light to track the flash power proportionally, so that relative brightness between lights looks similar to the final exposure. Modelling lights are much weaker than the flash and differ slightly in colour and position, so they are a guide, not a perfect preview; always confirm with test shots and the light meter. In a dim studio, bright modelling lights also help the camera focus and make subjects' pupils smaller, which some photographers prefer.

Continuous lights

Continuous lights stay on, so what you see is what you get. They are essential for video, helpful for beginners learning to see light, and useful for subjects such as food and products where photographers want to adjust light gradually while watching. Types include:

• LED panels and monolight-style LED fixtures: efficient, cool-running, dimmable, often bi-colour or full RGB, and available in powers from small panels to fixtures rated at several hundred watts or more. High-power LED monolights with Bowens mounts accept the same modifiers as strobes.
• Tungsten and tungsten-halogen lights: traditional film and television lights with excellent colour rendering and a warm colour temperature of about 3,200 K, but very hot, power-hungry and largely replaced by LEDs.
• Fluorescent banks: soft, cool-running lights once popular for video, now largely replaced by LEDs.
• HMI lights: very powerful daylight-balanced lights used in film production, rarely needed in stills studios.

Continuous lights are much less intense than flash, so photographers often need wider apertures, higher ISO or slower shutter speeds, which can limit depth of field and freezing motion. For portraits with continuous light, ISO 400 to 800 and apertures around f/2.8 to f/4 at 1/125 s are typical with a powerful LED in a softbox.

Colour quality

Accurate, pleasing colour depends on a light's spectrum. Studio flashes produce a broad spectrum similar to daylight, around 5,500 to 5,800 K, although colour temperature can shift slightly with power setting; many modern units offer colour-consistency modes. LED quality varies greatly: inexpensive LEDs may have gaps in their spectrum that make skin look grey or greenish and render some product colours inaccurately. Metrics such as CRI (colour rendering index), TLCI (television lighting consistency index) and TM-30 measure colour fidelity; for professional work, look for values of 95 or higher. Mixing lights from different manufacturers or types can produce slight colour differences between key and fill, so test them together and correct with gels or white balance where needed.

Mains and battery power

Mains-powered lights provide unlimited shooting and consistent recycling, but need outlets, cables and attention to circuit capacity (Lesson 11). Battery-powered strobes and LEDs free the photographer from cables, which reduces tripping hazards and makes it easy to rearrange the studio or work on location. Batteries must be charged and replaced, and continuous LEDs drain batteries quickly at high power, while battery strobes can often deliver several hundred full-power flashes per charge. Many photographers now use battery strobes in the studio as well as on location for their convenience.

Choosing a starter kit

A practical starter kit for portrait studio lighting might include two monolights or battery strobes of about 300 to 600 Ws, a radio trigger compatible with your camera, a medium softbox or octabox, a shoot-through or reflective umbrella, a reflector, a strip box or grid for a hair or rim light, sturdy stands and sandbags, and a background system. Choosing lights within one system lets you control them all from a single trigger and share modifiers. As your work grows, add lights and modifiers to solve specific problems. Buying good stands and safety equipment early is wise: an inexpensive light on a sturdy stand is safer and more useful than an expensive light on a flimsy one.

Flash systems and compatibility

Most studio flash brands form closed systems, in which flashes, triggers, battery packs and controllers work together through proprietary radio protocols. Godox, with its X system, sells under several names in different markets and offers a very wide range of lights at modest prices; Profoto, Broncolor and Elinchrom offer premium systems with high consistency and durability; and camera makers produce speedlights that integrate closely with their cameras. Choosing one system for all lights simplifies control from a single transmitter and allows batteries and accessories to be shared. Check that triggers are available for your camera brand, and consider whether the system offers the range of lights you may need later, from small speedlights to powerful pack systems.

Continuous light for stills and video

Hybrid photographers who shoot both stills and video often choose powerful LED fixtures so that one lighting kit can serve both. For stills, continuous light offers a true preview and allows wide apertures for shallow depth of field without ND filters, but limits motion freezing and requires higher ISO or slower shutter speeds. For video, continuous light is essential and should be flicker-free at the frame rates and shutter speeds used. When planning a kit for both, consider output in lux at 1 m with typical modifiers, colour quality, fan noise for video sound, and the ability to run on batteries. Many productions combine strobes for stills with LEDs for video in the same session, switching between them.

Rental and testing

Renting lights before buying is an excellent way to compare systems, test them in your own space, and discover what you need. Rental houses in most cities stock popular strobes, LEDs and modifiers by the day or weekend. Test recycling at full power, colour consistency between shots and across power settings, ease of control from the trigger, build quality of mounts and knobs, and the feel of the modifiers you plan to use. Notes from these tests make buying decisions much easier and help avoid expensive mistakes.

Maintenance and care of lights

Lights last longer with simple care: transport them in padded cases, cap flash tubes and modelling lamps, keep vents clear of dust, avoid knocking heads while warm, coil cables loosely without kinks, and update firmware when manufacturers release fixes. Record serial numbers for insurance and keep a log of any faults.