Softbox Size Calculator -- Ideal Modifier Size

A general rule is the softbox should be at least as large as your subject. For headshots, a 60-80cm softbox works well. For half-length portraits, 90-120cm. For full-length, 120-180cm. Larger softboxes produce softer light with smoother shadow transitions.

Yes, dramatically. A softbox closer to the subject appears larger (relative to the subject) and produces softer light. Moving the same softbox further away makes it appear smaller, producing harder light. The apparent size (softbox size / distance) determines softness, not the physical size alone.

Apparent size is the angular size of the light source as seen from the subject. The sun is a large light source but appears small (0.5°) because of its distance, producing hard shadows. A 120cm softbox at 1m has a much larger apparent size, producing soft shadows. Apparent size = modifier size / distance.

At the same size and distance, they produce similar softness. Softboxes offer more control (less spill, can add grids). Umbrellas are lighter, cheaper and set up faster. Shoot-through umbrellas are slightly softer than reflective ones. For the softest light, use the largest modifier you can place as close as possible.