Power. The monolight’s main advantage is that it creates a much more powerful flash of light than a traditional camera-mounted speedlight can. This light will travel farther and cover a larger area. There are also advantages as far as flash duration and recycle time (how fast the strobe can fire again) are concerned, which we will cover shortly.
Powerful monolights can even be used outdoors on sunny days to further control, supplement, or add to the sunlight falling on a subject—or to “overpower the sun,” as the expression goes.
“Watt seconds” is a unit of energy (equivalent to the joule) that, when related to monolights, measures strobe power. The higher the number, the brighter the light.
A deeper discussion on strobe power can get very involved and complex, but, for a photographer with a small studio who is creating headshots and still life images, monolights around 250Ws should provide sufficient power (brightness). Those using larger studios to create full-body portraits or fashion images, freezing motion, or maybe shooting outdoors, should look at strobes around 500 to 600Ws. If you think more power will be needed, you’ll be looking at monolights around 1000Ws or higher.
As we said above, the purpose of a strobe is to emit a powerful and brief flash of light, but sometimes you don’t need the flash to be at maximum brightness. Another thing to consider when shopping for a monolight is the ability to dim the flash’s brightness. Flash power is measured in f-stops, with each f-stop being twice as bright as the previous one. Strobe lights can control the flash output up to 10 stops.
To give an example of strobe power control, a monolight with 8 stops of control will be able to fire the strobe with half the light that a 7-stop monolight will give at its minimum power.
The speed at which a strobe re-energizes and can fire again is called “recycle time.” When a strobe light flashes, stored energy in the monolight’s capacitor is released to create the discharge of energy we see as a flash of light. Before the strobe can flash again, that discharged energy needs to be replaced.
If you are doing still life photography where the subject does not move, recycle time is not a big consideration when choosing a monolight. However, if you have a live model who is changing poses and expressions, you’ll want the strobe to be responsive to rapid shooting of the camera. A fast recycle time can be the difference between getting the perfect shot or missing the moment entirely.
Note: If a blazing fast recycle time is required for your photography, you might want to look at power packs and strobe lighting for your needs, because they generally provide faster recycling than a monolight.
A modeling light is a continuous light source that is built into the monolight. While not as bright as the flash of a strobe, the modeling light will show you how the strobe’s light will fall on your subject, as well as simply light the scene while you get your subject ready for the flash.
Modeling lights are typically LED or tungsten lamps. LEDs use less power, last longer, and generate less heat than tungsten bulbs, but their purpose remains the same. Tungsten modeling lamps are the traditional type used in monolights, but LEDs have steadily been replacing them in the recent past.
The camera and monolight need to be in sync—the monolight should flash when the camera’s shutter is open. This synchronization is wireless with modern monolights.
Some monolights have built-in radio receivers that fire on command from a transmitter connected to the camera—usually by mounting the transmitter to the camera’s hot shoe. Other monolights require a separate flash trigger system (transmitter and receiver) to be purchased.
TTL (“through the lens”) refers to the ability of a monolight (or camera speedlight) to adjust its power automatically with information from the camera’s light meter. The camera will meter the scene and adjust the flash power accordingly.
Non-TTL strobes leave it to the photographer to adjust flash power manually for a given scene.
A TTL-capable monolight requires a transmitter that is compatible with your camera brand. TTL-capable monolights can also be used in non-TTL mode-permitting manual power adjustments. They can even be used in non-TTL mode with other brands of cameras.
Like flashes of lightning in nature, not all monolights have the same flash duration. Having a short and powerful flash duration is the key to freezing fast action. For normal portraiture, a super-short flash duration might not be needed.
While there are different ways that manufacturers measure flash duration (and some monolights do not have their flash duration speeds published), if your goal is to freeze high-speed action with your monolight, a flash duration of around 1/2000 second is desirable.
Until relatively recently, all monolights were powered from a cord plugged into a power outlet in a wall. Now, many monolights are powered by rechargeable batteries. Battery power was a game-changer for monolights because it allowed photographers to fire powerful monolight strobes outdoors, or on location far from power outlets.
As attractive as that flexibility is, battery power is, of course, limited to the life of the battery and the need to recharge, so wall-powered monolights certainly still have a place in the studio photography world. Some battery-powered monolights allow you to operate the units while plugged into the wall in the studio and then run them using batteries when in the field, for maximum flexibility.
While many photographers have created beautiful images with a single monolight, you will find that many basic indoor lighting setups can be achieved with two to three strobes while larger or more complex shoots can easily utilize more than twice that number.
If you’re shooting outdoors, often a single-light setup can pair perfectly with the ambient light.
With three monolights in the studio, you can illuminate two sides of your subject and even throw light on a backdrop or backlight your subject—this is often called a “hair light.”
You can always start with a single monolight and add more as your budget allows or needs grow.
It is rare that you would point a monolight at your subject without modifying the flash in some way. Common light modifiers for monolights include umbrellas, softboxes, reflectors, grids, snoots, barndoors, and gels.
Some light modifiers, especially umbrellas, mount universally across different brands and types of monolights, but some brands have proprietary mounting systems that require special adapters for mounting different brands of light modifiers.