How big should my softbox be?

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.

Does distance affect softness?

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.

What is the apparent size of a light source?

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.

Softbox vs umbrella -- which is softer?

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.

Softbox Size Calculator -- Ideal Modifier Size

Find the ideal softbox size for your subject and light-to-subject distance.

Subject Width

Width of your subject (e.g. 40cm for headshot, 60cm for half-length)

Light-to-Subject Distance

Distance from softbox to your subject

Shoot TypeThe type of shot determines how much coverage you need

Modifier ShapeModifier shape affects coverage pattern and catchlight appearance

How We Calculate This

This calculator recommends softbox size based on subject size, shoot type, and modifier shape:

Ideal Size

Softbox size = subject width × shoot-type multiplier

Apparent Size Ratio

Apparent size = softbox size ÷ distance

Wrap Angle

Wrap = 2 × arctan(softbox size ÷ (2 × distance))

This is the angular size of the softbox as seen from the subject — the same physics that makes the sun (angular size ≈ 0.5°) a hard source despite its enormous physical size. A larger apparent size means softer, more wrapping light.

A note on the multipliers

The shoot-type size factors (headshot, half-length, full-length, product, group) are practical rules of thumb, not derived constants. They build on the well-established base rule that a softbox should be at least as large as your subject (cf. Lencarta "Which is the right softbox for you?" and Strobist "Lighting 102: Apparent Light Size"). Treat the recommended size as a sensible starting point — adjust to taste and to the space you have.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates based on standard optical and photographic formulas. Results may vary with specific equipment.