Luminance & Display Brightness Converter

Photometry, Display Engineering & Luminance Metrology

Luminance is the luminous intensity per unit projected area in a given direction, representing perceived surface brightness:

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• Universal Luminance Conversion Formulas (CIE Standards)**:

1 Foot-Lambert (fL) = (1) / (π) cd/ft^2 = 3.426259 cd/m^2 = 3.426259 Nits

L_fL = L_Nits3.426259 = L_Nits × 0.2918635

1 Apostilb (asb) = (1) / (π) cd/m^2 = 0.31831 Nits 1 Nit = π asb ≈ 3.14159 asb

1 Stilb (sb) = 1 cd/cm^2 = 10,000 Nits | 1 cd/in^2 = 1,550.003 Nits

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• Lambertian Emitter Luminous Flux & Inverse Square Illuminance**:

Φ = π × L_nits × A (Total Emitted Lumens, lm)

E = L_nits × Ad^2 (Viewer Incident Illuminance in Lux, lx)

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• Standard Display & Photometric Benchmarks**:

• DCI Commercial Cinema: 14.0 fL 47.97 Nits (Standard movie theater)

• Standard SDR Office Monitor: 250.0 Nits 72.97 fL 785.4 asb

• VESA DisplayHDR 1000: 1,000.0 Nits 291.86 fL Φ = 314.2 lm (0.1m^2)

• Outdoor Smartphone Mode: 2,000.0 Nits 583.72 fL

• Full Moon Night Surface: 2,500.0 Nits 729.66 fL

How to Use This Calculator

Enter your Luminance Magnitude (L / Brightness) (e.g. 1000 in luminance), From Luminance Unit — choose from Nits (cd/m² - Display & Smartphone Standard), Foot-Lamberts (fL - Cinema / DCI Projector Standard), Apostilbs (asb = blondel = 1/π cd/m² - Optics), To Luminance Unit — choose from Foot-Lamberts (fL), Nits (cd/m²), Apostilbs (asb), Display / Emitter Surface Area (A in m²) (e.g. 0.10 in m²), Viewing Distance (d in meters) (e.g. 0.50 in m), and Display & Photometric Benchmark — choose from Custom Luminance Level, VESA DisplayHDR 1000 Screen (1,000 Nits = cd/m²) → 291.86 fL | 3,141.6 asb | 314.16 lm emitted (0.1m²), DCI Commercial Cinema Screen (14.0 fL = 47.97 Nits) → 150.7 asb | Standard movie theater brightness. Results update instantly as you type — adjust any value to compare scenarios.

The Formula

Conversion factors used in this calculator:

1 fL = 1/pi cd/ft

1 asb = 1/pi cd/m

1 Lambert = 10,000/pi cd/m

1 Stilb = 10,000 cd/m

Worked Example

A home theater calibrator setting up a projector finds that converting a cinema reference of 14.0 Foot-Lamberts yields 47.97 Nits, allowing precision calibration with standard digital luxmeters.

Understanding Your Result

Unit conversions are exact by definition within a given measurement system (e.g., 1 km = exactly 1,000 m). Cross-system conversions (metric to imperial) use defined exchange factors: 1 inch = exactly 2.54 cm; 1 pound = 0.45359237 kg. Round your converted result to match the precision of your original measurement — expressing more decimal places than your input justifies implies false accuracy. For regulatory, legal, or safety-critical applications, verify which measurement system is required by the applicable standard.