A softbox is a type of light modifier that’s used to produce soft, even lighting. The lightweight box is made of translucent cloth, wrapped around a wire frame and attached to a light source (usually a studio strobe or speed light) on a stand.
The interior cloth is white or silver, while the exterior black cloth prevents light from spilling out. The light bounces around and scatters in all directions inside the box, and is then directed outward through a layer of diffusion material. The result is evenly distributed directional lighting that’s easy to control.
The effect is similar to window lighting, and it can help reduce harsh shadows. Softboxes are often used for portraits but are also great for shooting subjects such as products, food, and fashion.
They come in a variety of sizes. The light becomes softer as the size of the box increases and as it’s placed closer to the subject. Soft light can help reduce contrast, soften shadow edges, and conceal imperfections.
You can move the box around — to the side, up or down, closer or further — to experiment with shadows, hardness of lighting, and other effects. If your images look flat, you can try placing the light at an angle. If you’re getting uneven or harsh lighting, try moving the box in front of the subject.
Further reading and examples of softboxes in action:
10 Different Lighting Effects Using Just One Softbox — Picture Correct
Using a Softbox - studio lighting beginners' guide — ePhoto Zine
5 Tips For Using a Studio Octagon Softbox — Seamless