Reflector Calculator — Reflected Light Intensity

This calculator estimates reflected fill light based on reflector properties:

Reflected Intensity

Reflected = incident light × reflectance

The reflectance presets (silver ≈ 90%, white ≈ 80%, gold ≈ 85%, soft gold ≈ 70%, translucent diffuser ≈ 50% transmission) are typical industry approximations — exact return varies with the surface, its condition and the bounce angle, so treat them as a guide.

Light Loss

Stops lost = −log₂(reflectance)

Silver loses about 0.15 stops, white about 0.32 stops, gold about 0.23 stops. For a translucent diffuser the same formula gives the transmission loss instead (50% transmission = −log₂(0.5) = 1.0 stop).

Effective Fill at the Subject

Effective fill = reflected × (1 / d²) × (size / 100 cm)

The bounced light then falls off with the inverse-square law from the reflector to the subject. We express it relative to a 1 m, 100 cm reference: at 2 m the fill drops to a quarter (×0.25), and a larger panel returns proportionally more fill. So a closer, bigger reflector gives stronger fill.

Key:Fill Ratio

Stops between key and fill = log₂(ratio)

Treating the direct/key side as 100% and the reflector return as the fill side, the approximate key:fill ratio tells you the contrast. Each stop is a factor of two: 2:1 ≈ 1 stop, 4:1 ≈ 2 stops. This is a planning approximation, not a metered reading.