A softbox is an enclosure designed to fit around an artificial light source, such as a flash tube or halogen lamp. Its reflective interior intensifies the light output and projects it through its only means of escape—the front diffusion screen. This creates a quality of light long appreciated by photographers and videographers, which resembles the softer light one might find streaming through a window. It also creates square or rectangular highlights in the reflective surfaces of your subjects. The "soft" name stuck because of the quality of light this type of modifier emits.
Early softboxes were made of hard materials such as plywood, unlike today's lightweight materials, such as polyester and nylon. However, the concept is the same—light is contained as it bounces inside an enclosure and is diffused through a translucent white panel.
Softboxes vs. Umbrellas
Since many photographers "step up" from the old diffusion standby, umbrellas, let's briefly explore the differences between umbrellas and softboxes.
An umbrella is incredibly easy to set up—no question about that, although softbox manufacturers like Chimera keep coming up with speed rings with jointed mounting holes that snap into place un-tensioned. Then there are also softboxes from companies such as Westcott, with umbrella-type action, so we at least have some partial parity here.
One of the few benefits of umbrellas is the round catchlights they create in a portrait subject's eyes—rectangular reflections just don't look as natural (unless you’re trying to replicate window light). Of course, you can use a circular mask over a square or rectangular softbox, but that's another step in setup. Then again, you could also purchase an octagonal softbox, but more about that later.
Softboxes and umbrellas condense and focus the 180-degree beam angle of the light source, no matter what size they are. When used at the same distance, a larger umbrella will have a wider beam angle than a smaller umbrella, and it's important to match its size with the size of the subject. In any case, umbrellas have a beam angle of approximately 135 degrees and lots of what's called “spill light” that's very hard to contain.
Softboxes, on the other hand, do contain the light and I think it's hard to dispute that they're much better at doing this than umbrellas. Out of the box, their beam angle is roughly 90 degrees. Spill light is greatly reduced and the light is easier to direct than the wider wash of the umbrella. In fact, major softbox makers produce optional honeycomb grids that reduce the beam spread to 60, 40, and even 20 degrees, which is a real benefit because the grid provides the directional control of a reflector with a soft, flattering quality of light and manageable contrast with open shadows. You're also less likely to have a piece of the softbox in your shot as you jockey for position on set to make light-intensity adjustments.
Umbrellas and softboxes have optional interiors of white, silver, or gold. One advantage of umbrellas is that on so-called convertible umbrellas, you can swap out the interior, although I wouldn't call the process easy. Softboxes, on the other hand, can accept additional diffusion inside for creating an even softer light. If you want to dive deeper into umbrellas and how they compare, Bjorn Petersen has put together another guide on how to choose one.
Although all softboxes aren't created equal, softboxes are more able to render diffused light—unless, of course, you are using a 6' umbrella. And you're able to regulate how much diffusion is available, depending on your needs. This is one reason to consider buying a softbox with a removable front diffusion panel. Most of these have removable interior baffles that thwart hot spots in the output. Major manufacturers make front diffusers of different strengths and some even have filter panels that convert the output to daylight or tungsten balance, depending on your source. In any case, you also have the option of not using any diffusion, which turns your softbox into one big reflector.
Sizes and Shapes
Choose the size based on the coverage you need for the subject and the quality of light that you're seeking. In general, you wouldn't use a 12 x 16" softbox for a full-length portrait unless you're doing it for effect, and you wouldn't use a 54 x 72" softbox for a head or small product shot. However, there is a quality of light consideration, related to size. The farther away your subject is, coupled with its size in relation to your softbox, the harder and harsher the light source. While not a “point light source,” the 12 x 16" softbox is a lot closer to that definition than the larger light bank, but you could match the 12 x 16" look if you pulled the 54 x 72" back far enough.
Put simply, the bigger the light source, the softer the rendering and the wider the beam angle, and therefore, the coverage. Also, the closer you move the softbox to your subject, the softer the wraparound light you get.
The softbox type governs the shape of the light you're putting on your subject. Much of a large softbox’s surface area is wasted on a headshot, for instance, but it's ideal for small- to medium-sized groups. This, among other factors, is the reason for different size and shape softboxes.
This is what most people think of when you say “softbox.” Longer on one side, they're ideal for full-length portraiture and vertical compositions in general. Some have speedrings are made to rotate so that you can orient the box in landscape mode for wide, horizontal coverage. A rectangular softbox casts window-shaped highlights in reflective objects, but the catchlights it creates in a portrait subject’s eyes are less than ideal.
A favorite of portrait studios, this shape works with most subjects, although there is some fall-off in full-length shots and catchlight rendition is much like the long rectangle. Square softboxes are great for low-ceiling shooting spaces, and their shape is ideal for head-and-shoulders portraiture and small groups.
The long, thin strip box is also capable of rendering soft, flattering light, but can be better confined and aimed when compared to the broad wash of standard rectangle, square, or octagonal banks. While the dimensions of a rectangular softboxes have a ratio of approximately 1:1.3, short side to long side, strip banks are about 1:4, making them ideal for edge or rim lighting to separate the subject from the background, and also overhead as a hair light for individuals or groups, depending on the size of the softbox. This shape is also handy for lighting backgrounds from above or below, and makes creating a “gradient” background easier for product photography. Strip banks create long, elegant highlights in glassware and other reflective objects.
Octagonal softboxes have become popular for their soft output, shallow design, and rapid fall-off as you get farther from a background. The octagon’s large surface area gives it a signature soft, wraparound quality of light that’s very flattering at virtually any point, on or off axis. The octagon has, arguably, the best rendering of natural-looking, circular catchlights in the subject’s eyes and, unlike the umbrella, there are no visibly distracting frames or spokes.
Probably the best softbox accessory ever made, the fabric grid folds flat when not in use and narrows the beam spread while maintaining a soft quality of light, with manageable contrast. Available in 20, 30, 40, and 60 degree spreads, grids add directional control as well as spill light control, making them valuable for use as edge lights or hair lights on a boom where an umbrella would just get in the way. Used on a main light, the grid nicely isolates the subject from the background for an elegant, painterly look.
Is there anything else you would like to know about softboxes? How about other diffusion and modifiers? Comment below with your questions!