Softbox Coverage Calculator

Softbox coverage and soft light

A softbox turns a small, hard source into a larger, softer one, and two things determine how soft and how broad the light is. Apparent size — how large the box looks from the subject’s position — sets softness: the closer and bigger the box relative to the subject, the softer the shadows; move it farther away and it behaves more like a hard source. Coverage — the lit area and spread angle — grows with distance, so a box close in gives soft but localized light, while moving it back widens coverage at the cost of softness and intensity (which falls off with the inverse-square law). The practical workflow: set distance for the softness you want first, then adjust power and any grid or diffusion to control spill.