Convertisseur de luminance et d'illuminance

Convertisseur de luminance et d'illuminance

Convert between every common photometric unit on one screen, with illuminance and luminance kept clearly apart so you never accidentally swap lux for nits. Type a value in any field and the rest of its group updates instantly.

Why Two Groups Instead of One

Illuminance (lux, foot-candle, phot, millilux, nox) measures light arriving at a surface — what a light meter reads on a desk or floor. Luminance (cd/m², foot-lambert, stilb, lambert, cd/ft²) measures light leaving a surface — what your eye actually sees coming off a screen, sky, or wall. They use different physical dimensions and you cannot convert between them without knowing the surface’s reflectance or geometry, so this tool keeps them separated.

Comment utiliser

1. Decide which quantity you have. Numbers off a lux meter or lighting spec sheet are illuminance; numbers off a display spec sheet (“600 nits peak”) are luminance.
2. Type your value into the matching field — every other field in that group updates immediately.
3. Adjust Decimal Precision if you need rounded values for a report or extra digits for engineering work.
4. Use Copy on any field for a single value, or Copy All to grab the full conversion list.

Caractéristiques

• Two clearly separated groups – Illuminance and luminance never mix, removing the most common photometric mistake.
• Ten units covered – SI (lux, cd/m²), imperial (foot-candle, foot-lambert, cd/ft²), CGS (phot, stilb, lambert), and historical (millilux, nox).
• Live bidirectional conversion – Type into any field, the others in the same group update on the next keystroke.
• Adjustable precision – From whole numbers up to ten decimal places, with automatic scientific notation for very large or very small values.
• Reference tables built in – See where typical scenes (moonlight, office, direct sun, smartphone screen, HDR mastering display) sit on each scale.
• Copy and reset – Single-click copy on every field, plus a Copy All button for grabbing the full conversion as plain text.

Cas d'utilisation courants

• Photographers and cinematographers matching foot-candles on an old American light meter to the lux readings on modern gear.
• Display and AR/VR engineers converting between cd/m² (nits) used in spec sheets and foot-lamberts used in projection and cinema standards.
• Lighting designers sanity-checking lux targets against IES, OSHA, or local code requirements written in foot-candles.
• Stage and architectural lighting teams reading old fixtures or papers that quote phot, stilb, or lambert.
• Students and physics tutors comparing CGS and SI photometric units side by side.

Conversion Math (For Reference)

• 1 foot-candle = 10.7639 lux (because 1 ft² = 0.092903 m²).
• 1 phot = 10,000 lux (1 lumen per cm²).
• 1 nox = 1 millilux = 0.001 lux.
• 1 foot-lambert = 10.7639 / π ≈ 3.4263 cd/m².
• 1 stilb = 10,000 cd/m² (1 candela per cm²).
• 1 lambert = 10,000 / π ≈ 3,183.10 cd/m².
• 1 cd/ft² = 10.7639 cd/m².