luminance converter
Unit ConvertersConvert Nits (cd/m²), Foot-lamberts, and Stilbs with real-time SMPTE Digital Cinema & HDR mastering standard matching, contrast visualizer, and projector lumens estimator.
Scientific Omni-Grid
Instant bi-directional photometric translation across all display science standards
SI standard photometric luminance for modern displays and monitors
SMPTE & DCI digital cinema projection benchmark (1 fL ≈ 3.426 cd/m²)
Imperial engineering metric for industrial light sources (1550 cd/m²)
CGS unit equal to 1 cd/cm² (10,000 cd/m²)
CGS photometric unit for perfectly diffuse surfaces (3,183.1 cd/m²)
Cinema & HDR Standard Matcher
Automated broadcast & cinematic certification matching based on calibrated luminance
Dynamic OLED Screen Simulation
Quantum Dot / Self-Emissive OLED
Real-time CSS bloom rendering simulates display backlight emission and peak HDR ocular halo.
Human Contrast & Glare Visualizer
Dynamic physiological simulation of human ocular adaptation and glare perception
Projection Sizing Estimator
Convert Foot-lamberts into raw projector ANSI Lumens based on screen geometry and optical gain
How to Use the Luminance Converter
Step-by-step instructions for converting display brightness, matching broadcast/cinema standards, and calculating projector screen sizing.
Enter Luminance in Any Unit
Type your target brightness into any field of the Omni-Grid (Nits / cd/m², Foot-lamberts, cd/in², Stilb, Lambert) or click a calibrated reference preset.
Instant Cross-Unit Conversion
The engine synchronously updates all metric SI units, imperial cinema units (fL), and legacy photometric units (Apostilb, Skot, cd/ft², cd/cm²).
Check Cinema & HDR Standard Compliance
Inspect the Cinema & HDR Matcher to verify compliance with industry standards (SMPTE 196M, ITU-R BT.709, VESA DisplayHDR, Dolby Vision, BT.2100) and target EOTF curves.
Evaluate Visual Perception & Glare Risk
Monitor the human visual regime (scotopic night vision, mesopic twilight, photopic SDR/HDR, or optical glare) along with simulated pupil diameter (2 mm to 8 mm).
Calculate Projector Lumens & Screen Sizing
Expand the Projection Sizing tool to compute the required projector output in ANSI Lumens based on screen diagonal, 16:9 area, and screen fabric gain (0.8 to 1.3).
Export Calibration Specifications
Click 'Copy Calibration Spec' to transfer a structured summary (target luminance, foot-lamberts, compliance tier, and viewing environment) to your clipboard.
Frequently Asked Questions (FAQ)
Comprehensive technical insights into luminance physics, display calibration, cinema projection standards, and human retinal adaptation.
Q:What is luminance and what is the difference between a Nit and a Candela per square meter (cd/m²)?
Luminance (L_v) is the photometric measure of luminous intensity emitted, reflected, or transmitted per unit surface area in a given direction: L = I / (A · cos θ). The standard SI unit is the Candela per square meter (cd/m²). In the display and broadcast industries, 'Nit' is simply a convenient synonym: 1 Nit = 1 cd/m². Luminance represents surface brightness as perceived by the human eye and is independent of viewing distance for an extended uniform light source.
Q:Why does cinema use Foot-lamberts (fL) while TV and HDR use Nits (cd/m²)?
The Foot-lambert is an imperial unit defined as 1/π cd/ft² ≈ 3.426 cd/m² (Nits). The motion picture industry historically adopted fL because an ideal Lambertian screen with unity gain (1.0) illuminated by 1 foot-candle of illuminance reflects exactly 1 Foot-lambert. SMPTE 196M established the commercial cinema theatrical standard at 14 ± 2 fL (approximately 48 Nits). Modern television, computer monitors, and HDR mastering adopted the metric Nit (cd/m²), ranging from 100 nits (BT.709 SDR) up to 1,000–10,000 nits (BT.2100 HDR).
Q:How do you calculate required projector ANSI Lumens from screen size and gain?
The relationship between projector luminous flux (Φ in ANSI Lumens), screen surface area (A), and screen gain (g) is: in imperial units, L_fL = (Φ_lumens · g) / A_sqft; in metric SI units, L_nits = (Φ_lumens · g) / (π · A_m²). For example, a 120-inch 16:9 projection screen has an area of approximately 42.3 sq ft (3.93 m²). Achieving reference cinema brightness of 16 fL (~55 Nits) with a unity gain (1.0) screen requires at least 677 ANSI Lumens, with 1,000+ Lumens recommended for lamp aging headroom.
Q:What are the peak luminance targets for VESA DisplayHDR and HDR mastering?
VESA DisplayHDR standards specify minimum sustained peak luminance: DisplayHDR 400 (400 nits, entry-level), DisplayHDR 600 (600 nits, local dimming), DisplayHDR 1000 (1,000 nits, 0.05 nit black floor for LCD), and DisplayHDR 1400 (1,400 nits, professional contrast). Broadcast and film mastering (Dolby Vision and HDR10) commonly grades content on 1,000 to 4,000 nit reference monitors, while the ITU-R BT.2100 Perceptual Quantizer (PQ) curve establishes a theoretical maximum headroom of 10,000 nits.
Q:How does human vision adapt across scotopic, mesopic, and photopic luminance ranges?
Human vision transitions across three physiological regimes: Scotopic vision (< 10⁻³ cd/m²) relies solely on rod photoreceptors (monochromatic, fully dilated ~8 mm pupils in starlight). Mesopic vision (10⁻³ to 3 cd/m²) engages both rods and cones (twilight, moonlight, and dark cinema theaters). Photopic vision (> 3 cd/m²) operates purely via cone photoreceptors for high visual acuity and full color perception. Above 10,000 cd/m², excessive brightness constricts pupils to ~2 mm and induces discomfort glare or visual saturation.
Q:How do you convert between Nits (cd/m²) and older photometric units (Stilb, Lambert, Apostilb)?
The exact conversion factors to standard SI Nits (cd/m²) are: 1 Stilb (sb) = 1 cd/cm² = 10,000 cd/m²; 1 Lambert (L) = 10,000 / π cd/m² ≈ 3,183.10 cd/m²; 1 Candela per square inch (cd/in²) = 1 / 0.00064516 cd/m² ≈ 1,550.00 cd/m²; 1 Foot-lambert (fL) = 10.7639 / π cd/m² ≈ 3.42626 cd/m²; 1 Apostilb (asb / blondel) = 1 / π cd/m² ≈ 0.31831 cd/m²; and 1 Skot (sk) = 10⁻³ asb ≈ 0.00031831 cd/m².
- L: Luminance in Candelas per square meter (cd/m²) or Nits.
- I: Luminous intensity in Candelas (cd).
- A: Surface emitting or reflecting area (m²).
- θ (Theta): Angle between the surface normal and the line of sight.
- fL: Foot-lambert, defined as (1/π) cd/ft² for a perfectly lambertian diffuse reflector.
- Gain: Optical screen reflective efficiency relative to standard magnesium oxide (unity = 1.0).
Luminance converter Table
| Unit | cd/m² | cd/cm² | cd/ft² | cd/in² |
|---|---|---|---|---|
| 1 cd/m² | 1 | 0.0001 | 0.0929031299 | 0.00064516 |
| 1 cd/cm² | 10,000 | 1 | 929.0312990645 | 6.4516 |
| 1 cd/ft² | 10.7639 | 0.00107639 | 1 | 0.0069444377 |
| 1 cd/in² | 1,550.0031 | 0.15500031 | 144.0001393547 | 1 |
What is luminance converter?
Convert Nits, Foot-lamberts, and Stilbs instantly with our multi-metric platform. Features real-time SMPTE Digital Cinema standard matching, a dynamic OLED simulator, and an advanced projector lumens estimator. The Human Contrast & Glare Visualizer uniquely simulates human pupillary adaptation, allowing you to anticipate visual fatigue and glare under mesopic twilight conditions. This is the definitive tool for transitioning flawlessly between SDR projection and high-peak HDR mastering.
Practical Calculation ExampleA home theater installer in Los Angeles is configuring a high-end laser projector for a 120-inch acoustically transparent screen. They input the target Foot-lamberts into the Scientific Omni-Grid to ensure compliance with SMPTE digital cinema standards. Using the Projection Sizing Estimator, they calculate the exact ANSI lumens required by factoring in the specific screen fabric gain. Satisfied with the math, they click Copy Calibration Spec to attach the precise hardware requirements to their client's purchase order.
Display Science Reference Zones| Interface Element | Display Engineering Function | Practical Industry Application |
|---|---|---|
| SCIENTIFIC OMNI-GRID | Multi-Standard Conversion | Seamlessly translates between SI metric Nits (cd/m²), cinema Foot-lamberts (fL), imperial cd/in², and scientific CGS Stilb/Lambert units with zero latency. |
| CINEMA & HDR STANDARD MATCHER | Compliance Verification | Instantly checks target values against SMPTE 196M (14 fL cinema), ITU-R BT.709 studio mastering (100 nits), VESA DisplayHDR tiers, and Dolby Vision 1,000-nit standards. |
| CONTRAST & GLARE VISUALIZER | Ocular Adaptation | Simulates human eye response from scotopic night vision (< 5 nits) and mesopic cinema darkroom viewing to photopic high glare (> 1,500 nits). |
| PROJECTION SIZING ESTIMATOR | Optics Calculation | Calculates the exact raw ANSI projector lumens needed to hit target Foot-lamberts on screens from 100" to 200" with variable screen fabric gain. |
History and Origin
The foundation of measuring luminance dates back to the standard candle, originally used to define the candela. The Foot-lambert, heavily utilized in the United States, was established to standardize the brightness of early cinema screens. Today, as high dynamic range displays push the boundaries of visual technology, the Nit (candela per square meter) has become the undisputed global metric for calibrating televisions, monitors, and modern digital cinemas.