luminous intensity
Enable an agent to identify, interpret, compare and evaluate the luminous intensity of a light source in a specified direction under stated photometric and measurement conditions.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
recalled by Codex without web access - no source was read
Researched by: Codex
Purpose and description
Enable an agent to identify, interpret, compare and evaluate the luminous intensity of a light source in a specified direction under stated photometric and measurement conditions.
Luminous intensity is the luminous flux emitted by a source per unit solid angle in a specified direction, with radiant power weighted by a specified spectral luminous efficiency function representing human vision.
It can be Recognize whether a reported light quantity is luminous intensity and normalize compatible units.; Compare directional values after checking weighting, geometry, temporal basis and operating conditions.; Inspect an angular distribution to locate peaks, weak directions and coverage gaps.; Derive luminous intensity from suitable radiometric or illuminance measurements when the required assumptions are supported.; Integrate a sufficiently sampled intensity distribution over solid angle to estimate luminous flux.; Evaluate a specified directional-intensity requirement while accounting for uncertainty and incomplete angular coverage..
Distinguishing features
A luminous-intensity claim specifies a direction or directional distribution and uses candela, equivalent to lumen per steradian; a lumen value alone describes luminous flux.
It describes directional emission from a source, whereas illuminance describes luminous flux incident per unit receiving area.
It does not divide by projected emitting area; a quantity expressed in candela per square metre is luminance.
It weights optical radiation using a specified photometric convention rather than reporting unweighted radiant power per solid angle.
It is a measurable photometric quantity, not a direct report of perceived brightness; identical candela values can produce different visual experiences.
Scope
+ Luminous intensity as luminous flux per unit solid angle in a specified direction
+ Values expressed in candela and their angular, temporal and operating conditions
+ The photometric weighting that connects radiant intensity to luminous intensity
+ Directional distributions, peak values and explicitly defined angular averages
+ Measurement geometry, calibration, uncertainty and conditional derivations
- Total luminous flux as an independently modelled quantity
- Illuminance at a receiving surface and complete lighting-layout design
- Luminance distributions over emitting or reflecting surfaces
- Subjective brightness, visual comfort and glare assessment
- The construction, electrical efficiency and lifecycle of lamps or luminaires
- Radiant intensity and spectral emission except where needed to establish a photometric value
Characteristics
- Luminous intensity
- candela (cd), equivalent to lumen per steradian (lm/sr) Provides the directional photometric magnitude being modelled.
- Emission direction
- Direction relative to a declared source coordinate system; angles in degrees or radians An intensity value can change substantially with direction and is incomplete without its directional meaning.
- Angular sampling and acceptance
- Sampling intervals in degrees or radians; detector acceptance in steradians Finite angular resolution can smooth narrow peaks and make nominally identical measurements differ.
- Photometric weighting convention
- Named spectral luminous-efficiency function, normalization and applicable standard Establishes how the radiation spectrum contributes to the reported photometric quantity.
- Temporal basis
- Steady-state, instantaneous, time-averaged or pulse-related value with the averaging or evaluation rule stated Prevents comparison of peaks, averages and specialized flashing-light metrics as if they were equivalent.
- Source operating condition
- Drive setting, temperature, stabilization state and optical configuration Connects a value to the source state that produced it.
- Measurement geometry
- Source extent, reference centre, detector distance and orientation, and propagation conditions Determines whether a directional measurement or an illuminance-based derivation is valid.
- Measurement uncertainty
- Absolute uncertainty in cd or relative uncertainty in percent, with coverage information Supports defensible comparisons and decisions near a specified limit.
Also called
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 6 bundles · 11 layers · 19 findings · 29 questions.
Quantity identity Establishes what a luminous-intensity statement denotes and separates it from neighbouring light quantities.
Light-output claims often conflate directional emission, total output, surface illumination and perceived brightness.
Directional definition
Identifies intensity as the directional density of luminous flux over solid angle.
Flux per solid angle
Luminous intensity is expressed as I_v = dΦ_v/dΩ. Dividing flux by a finite solid angle establishes an average over that region rather than necessarily the value in one direction.
- Does the claim describe intensity in a specified direction or an average over a finite angular region? definition
- What evidence establishes that the reported unit is candela or an equivalent lumen-per-steradian expression? measurement
Neighbouring quantities
Tests whether a statement belongs to luminous intensity or another photometric or perceptual model.
Quantity boundary tests
The model distinguishes directional source output from total flux, receiving-surface illuminance, emitting-surface luminance and subjective brightness.
- Is the value attached to an emission direction, a receiving area, a projected emitting area or the source's total output? boundary
- If the claim uses the word brightness, what operational definition determines whether it belongs in this model? definition
Spectral photometric basis Records how optical radiation is weighted to yield the reported luminous intensity.
Equal radiant intensities at different wavelengths need not produce equal luminous intensities.
Visual weighting
Establishes the spectral response convention behind a photometric value.
Declared weighting function
Conventional photopic luminous intensity uses the photopic luminous-efficiency function. Values using another visual-response convention require explicit identification before comparison.
- Which luminous-efficiency function and normalization define this reported value? definition
- Which standard, instrument specification or calculation record establishes that convention? provenance
Radiometric conversion
Checks whether spectral radiant-intensity evidence supports a photometric calculation.
Spectrum-dependent conversion
Conversion from radiant intensity requires the relevant spectral distribution and weighting; a broadband watt-per-steradian value alone generally does not determine candela.
- Is spectral radiant intensity available for the same direction and source operating condition? measurement
- Do the spectral range, resolution and normalization support the proposed integration, or must the conversion remain unresolved? action
Angular emission Describes how luminous intensity varies around the source and how directional summaries are obtained.
A single candela value can hide the difference between a narrow beam and broad angular coverage.
Direction reference
Anchors every direction to the source and its optical configuration.
Source coordinate system
Directional values require declared axes, angular conventions and source orientation so that measurements refer to the same physical directions.
- What axes and angular convention locate the reported direction relative to the source? definition
- Which optical configuration and mounting orientation were present when the distribution was obtained? provenance
Distribution summaries
Interprets peak intensity, angular averages and flux estimates from sampled distributions.
Sampling and summary validity
Peak detection depends on angular resolution, while averages and flux integration require solid-angle weighting and sufficient coverage. Symmetry must be supported before filling unmeasured directions.
- Is angular sampling fine enough to resolve the narrowest relevant peak, and what detector acceptance smooths the observations? measurement
- What measured coverage or supported symmetry permits the proposed angular average or luminous-flux estimate? action
Measurement validity Establishes whether an observation or calculation credibly measures directional luminous intensity.
Distance, alignment, source extent and detector response can invalidate a seemingly straightforward candela result.
Photometric geometry
Checks the geometric and propagation assumptions used to obtain intensity.
Illuminance-based inference
For an adequately point-like source under suitable propagation conditions, illuminance obeys E_v = I_v cos(α)/r², where α is the incidence angle to the receiver normal. Extended-source near-field measurements need a more appropriate treatment.
- Does the source size, distance and beam behaviour justify the point-source approximation at the detector? boundary
- How were distance, receiver orientation, background light and propagation losses established or corrected? measurement
Calibration and error
Connects the reported value to calibration evidence and an uncertainty assessment.
Photometric traceability
Credibility depends on applicable calibration and treatment of spectral mismatch, alignment, detector response and source stability.
- What calibration record establishes traceability for the instrument and measurement configuration? provenance
- Which uncertainty contributions dominate, and what coverage statement accompanies the reported uncertainty? measurement
State and use Connects luminous-intensity values to source operation, temporal behaviour and a concrete decision.
A valid measurement is useful only when its conditions and interpretation match the intended comparison or requirement.
Operating and temporal state
Identifies the source state and time basis represented by the value.
Conditional intensity value
Drive level, temperature, stabilization and modulation can change intensity. Peak, time-averaged and application-specific effective flashing intensity require separate interpretations.
- At what drive setting, temperature, stabilization state and optical configuration was intensity evaluated? measurement
- Does the value represent instantaneous intensity, a defined time average or an effective flashing-light metric under a named method? definition
Decision conditions
Determines whether available intensity evidence supports a requested comparison or acceptance decision.
Directional requirement evaluation
A directional requirement must identify its angular region, operating conditions, temporal basis and decision rule; a peak value alone cannot establish minimum coverage.
- Does the requirement constrain a peak, a particular direction, an angular average or every direction within a region? definition
- Given uncertainty and unmeasured directions, can the agent accept or reject the claim, or must it request additional measurements? action
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Check these first
Recalled without web access and unsourced; every item is a lead to verify.
- Ordinary lighting specifications generally use photopic weighting; verify the weighting function before comparing specialized measurements.
- No source-specific operating ranges or jurisdiction-specific requirements are asserted.
- Standards and terminology are recalled from established knowledge; editions and exact wording have not been checked.
- Which of these check these first hold for the sense of luminous intensity this model covers, and on what evidence? provenance
Kinds and varieties
Recalled without web access and unsourced; every item is a lead to verify.
- Photopic luminous intensity
- Scotopic luminous intensity
- Which of these kinds and varieties hold for the sense of luminous intensity this model covers, and on what evidence? provenance
Identifiers and schemes
Recalled without web access and unsourced; every item is a lead to verify.
- SI quantity symbol - I_v - Conventional symbol for luminous intensity; the subscript distinguishes it from radiant intensity.
- SI unit symbol - cd - The candela is the SI base unit of luminous intensity; one candela equals one lumen per steradian.
- Which of these identifiers and schemes hold for the sense of luminous intensity this model covers, and on what evidence? provenance
Standards and regulation
Recalled without web access and unsourced; every item is a lead to verify.
- BIPM SI Brochure: defines the candela using the fixed luminous efficacy of monochromatic radiation at 540 × 10^12 Hz.
- CIE spectral luminous efficiency functions: provide the visual weighting used in photometric quantities.
- CIE International Lighting Vocabulary: standardizes terminology for luminous intensity and related quantities.
- Which of these standards and regulation hold for the sense of luminous intensity this model covers, and on what evidence? provenance
Real-world use
Recalled without web access and unsourced; every item is a lead to verify.
- Specifying the directional output of LEDs, lamps and luminaires.
- Characterizing beam patterns of vehicle lamps and signal lights.
- Assessing the directional visibility of navigation and warning lights.
- Calculating illuminance from a source when its distance, direction and measurement geometry are known.
- Calibrating photometric instruments and reference light sources.
- Which of these real-world use hold for the sense of luminous intensity this model covers, and on what evidence? provenance
Typical measurements
Recalled without web access and unsourced; every item is a lead to verify.
- Luminous intensity - Nonnegative; no universal typical range because values depend on source, direction and beam concentration. - cd
- Angular luminous intensity distribution - Measured over specified emission directions; angular coverage depends on the application. - cd as a function of angle
- Which of these typical measurements hold for the sense of luminous intensity this model covers, and on what evidence? provenance
Failure modes and hazards
Recalled without web access and unsourced; every item is a lead to verify.
- Confusing luminous intensity with total luminous flux obscures the effect of beam concentration.
- Confusing luminous intensity with luminance gives misleading conclusions about apparent surface brightness and glare.
- Spectral mismatch between a detector and the intended visual weighting function introduces measurement error.
- Inferring intensity from illuminance using an inverse-square relationship outside suitable far-field geometry produces inaccurate results.
- Treating a candela value alone as an assessment of eye safety ignores spectrum, source size, exposure duration and viewing geometry.
- Which of these failure modes and hazards hold for the sense of luminous intensity this model covers, and on what evidence? provenance
Regional variation
Recalled without web access and unsourced; every item is a lead to verify.
- The SI quantity and candela unit are internationally shared; application-specific lighting requirements differ by jurisdiction.
- Which of these regional variation hold for the sense of luminous intensity this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Recalled without web access and unsourced; every item is a lead to verify.
- Luminous flux - Luminous flux measures visually weighted light output in lumens; luminous intensity measures that output per unit solid angle in a direction.
- Illuminance - Illuminance is incident luminous flux per unit receiving area, measured in lux.
- Luminance - Luminance expresses directional luminous intensity per unit projected source area, measured in cd/m².
- Radiant intensity - Radiant intensity measures radiant power per unit solid angle in W/sr without human visual weighting.
- Brightness - Brightness is a perceptual attribute; luminous intensity is a defined photometric quantity.
- Candela - Candela is the measurement unit; luminous intensity is the quantity measured.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of luminous intensity this model covers, and on what evidence? provenance
What the second pass must settle
- Which authoritative photometric vocabulary and standard editions should govern this registry entry's definitions and measurement terminology?
- Should this entry include scotopic, mesopic and effective flashing-light quantities as explicitly qualified variants, or link them to separate neighbouring concepts?
- Which source-specific criteria should establish adequate measurement distance and angular resolution for extended sources and narrow beams?
- Which minimum provenance and uncertainty evidence should be required before an agent uses a reported candela value for an acceptance decision?
- Does an existing Vercy world model already own luminous intensity, requiring this registry entry to link to that model rather than create a second publication?