ISO 80000-7: Quantities and Units of Light and Radiation

ISO 80000-7 codifies the quantities that describe visible light and adjacent radiation so photometry, radiometry, and illumination engineering share the same set of names, symbols, and coherent SI units. Use this reference when you need to align laboratory measurements, lighting calculations, or camera exposure settings with internationally recognised terminology.

Ground your understanding by revisiting the International System of Units guide and the ISO 80000-1 general principles article so the candela definition and angular units are clear before translating manufacturer datasheets. When optical power flow couples with electrical drive circuits, pair this chapter with the ISO 80000-6 electromagnetism guide and calculators like the lux to lumens converter to confirm that lighting control systems remain consistent from sensors to reports. For a deep dive into the constant-based definition of luminous intensity, read the candela base unit explainer before finalising photometric traceability plans.

ISO 80000-7 also interacts with energy and thermal analyses because lighting contributes to heat loads and comfort studies. Cross-check findings with the ISO 80000-5 thermodynamics guide when estimating HVAC impacts, and consult the part-by-part quick tables to explore neighbouring standards such as acoustics or radiological health. For sound fields that share logarithmic level concepts with photometry, continue to the ISO 80000-8 acoustics reference and align multi-physics analyses in one terminology set.

Dive deeper into the geometry that underpins luminous intensity by studying the steradian explainer and revisit plane angles in the radian guide before translating luminous intensities into beam patterns. When comparing photometric reports with acoustic or RF level data, use the decibel overview so logarithmic ratios share consistent notation across disciplines.

What ISO 80000-7 covers

Photometric traceability

Connects luminous quantities to the candela so visual perception metrics such as illuminance and luminance stay compatible with SI-based lighting regulations.

Radiometric bridge

Translates radiant power, intensity, and exposure into coherent watt-based units that link optical power measurements to electromagnetic energy balances.

Spectral context

Describes how ISO 80000-7 applies spectral weighting—like the V(λ) luminous efficiency curve—so photometric and radiometric datasets can be compared or converted.

Application breadth

Supports interior lighting, outdoor photometry, machine vision, photography, remote sensing, and plant-growth studies with a shared vocabulary of symbols and units.

Explore the electromagnetic bridge Plan room lumens

Principal photometric quantities

These definitions apply the CIE standard observer curve to convert electromagnetic power into visually weighted quantities. Use them when specifying luminaires, calibrating lux meters, or documenting exposure values in photography.

Quantity Symbol Coherent unit ISO 80000-7 definition Practical usage
Luminous intensity I_v candela (cd) Power emitted by a source in a particular direction, weighted by the CIE 1931 photopic response; defined via the luminous efficacy of monochromatic radiation at 540 THz. Document directional output of LEDs or luminaires when evaluating glare and spacing criteria in lighting layouts.
Luminous flux Φ_v lumen (lm = cd·sr) Total luminous power emitted by a source across all directions; equals the angular integral of luminous intensity over a sphere. Compare lamp datasheets and verify total output when sizing fixtures using the room lighting lumens calculator.
Illuminance E_v lux (lx = lm/m²) Luminous flux incident per unit area on a surface, assuming photopic weighting. Map workspace lighting levels and convert lux readings to total lumens with the lux to lumens calculator for compliance reporting.
Luminance L_v candela per square metre (cd/m²) Directional luminous intensity per unit emitting area projected on a plane; relates perceived brightness of screens and reflective surfaces. Specify display panel targets and roadway surface brightness requirements with ISO-consistent units.
Luminous exposure H_v lux second (lx·s) Time integral of illuminance; quantifies accumulated luminous energy on a surface. Calibrate photographic exposure values and horticultural lighting schedules that rely on total light dose.
Luminous energy Q_v lumen second (lm·s) Time integral of luminous flux, equal to luminous exposure multiplied by illuminated area. Track flash outputs and emergency lighting discharge events where total luminous content matters.

Radiometric counterparts

Radiometric quantities treat light as electromagnetic energy without visual weighting. They are essential when modelling how light sources interact with sensors, materials, or biological systems before applying human-centric conversion factors.

Quantity Symbol Coherent unit ISO 80000-7 definition Practical usage
Radiant flux Φ_e watt (W) Total electromagnetic power emitted, transferred, or received, irrespective of visual response. Correlate optical power meter readings with thermal load calculations in laser processing or photobiology labs.
Radiant intensity I_e watt per steradian (W/sr) Directional distribution of radiant flux; serves as the radiometric analogue to luminous intensity. Model infrared emitter patterns for machine vision or security camera illuminators.
Irradiance E_e watt per square metre (W/m²) Incident radiant flux density on a surface before applying any spectral weighting. Quantify solar panel inputs or UV sterilisation exposure where biological weighting will follow.
Radiant exposure H_e joule per square metre (J/m²) Time integral of irradiance; equals the radiant energy received per unit area. Document UV curing doses and ensure additive manufacturing processes meet energy thresholds.
Spectral radiant flux Φ_λ, Φ_ν watt per nanometre (W/nm) or watt per hertz (W/Hz) Distribution of radiant flux over wavelength or frequency, enabling conversions between radiometric and photometric quantities via weighting functions. Analyse LED bins and daylight spectra before applying the V(λ) curve to obtain photometric values.

Workflow for ISO 80000-7 adoption

Standardise how your teams capture, convert, and report light measurements by following this playbook alongside training resources and calculators.

  1. Start with SI foundations

    Revisit the International System of Units guide and ISO 80000-1 general principles to confirm how the candela ties to fundamental constants and how steradian definitions underpin solid-angle calculations.

  2. Classify the measurement goal

    Determine whether the task is perception-centric (photometric) or energy-centric (radiometric). ISO 80000-7 clarifies symbol choices and conversion factors for each domain so reports remain unambiguous.

  3. Capture geometry and spectra

    Record emitting area, receiving area, directionality, and spectral content. These parameters decide whether you need luminance, illuminance, or irradiance tables and which weighting functions apply.

  4. Validate with calculators

    Translate field measurements into engineering decisions using tools like the lux to lumens converter or room lighting lumens planner to cross-check compliance targets.

  5. Document conversions

    Log any photometric–radiometric conversions, including the luminous efficacy value or spectral weighting used, so colleagues can reproduce results or feed them into simulations defined in ISO 80000-6 and ISO 80000-5.

Documenting conversions is especially important when lighting analyses feed into building energy models or electronics simulations governed by ISO 80000-5 and ISO 80000-6. Clear audit trails help colleagues and automated systems reproduce results without reinterpreting units.

Practice with photometry calculators

Reinforce ISO 80000-7 definitions by applying them to quick calculations that bridge sensor data, design targets, and compliance limits.

Further reading

Build a broader measurement strategy by combining ISO 80000-7 with adjacent chapters and foundational SI references. The resources below keep multidisciplinary teams on the same page.