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Luminous Unit Converter

Convert between luminous intensity (candela), luminance (nit, lambert), and illuminance (lux, footcandle) instantly.

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    💡 Overview: Convert Between Lux, Nit, Candela, and More

    The Luminous Unit Converter helps you switch between units that describe how light behaves—from how intense it is (candela), how bright it appears (nit), to how much light hits a surface (lux). These units are vital in engineering, photography, display technology, architecture, and lighting design.

    Light measurement is typically divided into three distinct quantities:

    • Luminous Intensity (candela, cd): Describes the amount of visible light emitted in a specific direction from a source.
    • Luminance (cd/m² or nit, lambert): Measures how bright a surface appears to the eye based on emitted or reflected light per unit area.
    • Illuminance (lux, footcandle): Measures how much luminous flux lands on a surface area.

    This converter is ideal for lighting professionals, AV engineers, photographers, interior designers, and hobbyists working with screens, light fixtures, or ambient lighting conditions.

    🧮 Formula & Methodology: Luminous Unit Conversions

    Each luminous measurement type has its own standard base unit:

    • Luminous Intensity: base is candela (cd)
    • Luminance: base is cd/m² (nit)
    • Illuminance: base is lux (lm/m²)

    To convert between units: 

    Step 1: Convert input → SI base unit
    SI_value = input × factor_from

Step 2: Convert SI base → target unit
    result = SI_value ÷ factor_to

    For example:

    • 1 nit = 1 cd/m²
    • 1 lux = 1 lumen/m²
    • 1 footcandle ≈ 10.7639 lux
    • 1 lambert ≈ 3183.1 cd/m²

    Note: Luminance and illuminance are different quantities and cannot be directly compared.

    📊 Example Calculations

    • 50 cd → candela-per-ft²: 50 cd ÷ 0.092903 = ~538.2 cd/ft²
    • 300 lux → footcandle: 300 lx ÷ 10.7639 ≈ 27.87 fc
    • 1000 cd/m² (nit) → lambert: 1000 ÷ 3183.1 ≈ 0.314 L
    • 800 fc → lux: 800 × 10.7639 = 8611.1 lx

    🌐 Real-World Use Cases for Luminous Unit Conversion

    • 🔳 Display brightness calibration: Monitor screens are measured in nits (e.g., 300–600 cd/m²)
    • 📸 Photography lighting setups: Controlled studio lighting requires ~300–1000 lux
    • 🏛️ Museum exhibit lighting: Artwork is preserved by limiting exposure to ~50–200 lux
    • 🏢 Office environment standards: Lighting recommendations suggest 300–500 lux
    • 🛠️ Workplace compliance: Health and safety standards often require minimum illuminance in footcandles

    ❓ Frequently Asked Questions

    What is candela (cd)?

    The SI base unit of luminous intensity. It measures the visible light emitted in a specific direction from a source like a bulb or LED.

    What’s a nit?

    1 nit equals 1 candela per square meter (cd/m²). It's commonly used in TV, monitor, and smartphone brightness specifications.

    What’s the difference between lux and footcandle?

    Both measure illuminance (light received per area). 1 footcandle = 10.7639 lux. Lux is metric, footcandle is imperial.

    Can I convert between candela and lux?

    Only with distance. Lux = luminous intensity (cd) ÷ distance² (in meters). So it's not a direct unit conversion without geometry.

    What is lambert used for?

    Lambert is a unit of luminance used in older photometry systems. 1 lambert ≈ 3183.1 cd/m². It's used in display and lighting contexts.

    Why is luminous intensity different from illuminance?

    Luminous intensity is about the light a source emits in a direction (e.g., spotlight). Illuminance is about light received on a surface.

    How do I measure brightness for my camera or setup?

    Use a lux meter for ambient light, and convert to footcandles if needed. Some older light meters display in fc.