Standard Illuminants User Guide

Standard Illuminants is a tabbed colorimetry workspace. The Lab tab is the active analysis surface, and the supporting tabs add analysis views, exports, and the Reference tab's standards and formulas behind the outputs.

• Lab: source mode, illuminant picker, CCT slider, comparison illuminant, surface reflectance toggles, chromatic adaptation pair, SPD chart, CRI chart, surface appearance, CAT matrix details, and comparison metrics.
• Chromaticity: the illuminants plotted in CIE 1931 xy, CIE 1976 u-prime v-prime, or CIE 1960 uv, with the Planckian locus, isotemperature lines, and dominant wavelength.
• Uncertainty: a Monte Carlo propagation of an editable measurement budget, reporting expanded uncertainty (k = 2), each input's contribution to u(CCT), and a 95% coverage region.
• Methods: observer, interval, and interpolation choices, with tables showing how the pipeline and the CCT method change the result, plus rendition metrics.
• Console: a query box (select, with, report, order by, limit) that runs illuminants through the same engine, with recipes, CSV and JSON output, and a two-column plot.
• Data: every dataset the tool uses, with its source and a Verbatim, Computed, Synthesised, or Absent status, and the features switched off for missing data.
• Export: SPD CSV export, JSON export, SPD PNG export, copied white HEX, share URL generation, share URL copy, and multi-illuminant comparison table.
• Reference, Standards: CIE 15:2018, CIE 13.3 CRI, IES TM-30, ISO 10526, ICC profile connection space, CIE A, D-series daylight, and F-series fluorescent summaries.
• Reference, Formulas: Planck blackbody, CIE daylight synthesis, SPD to XYZ integration, CRI method, TM-30 overview, Bradford CAT, CCT estimation, and color difference formulas.
• Reference, Citations: colorimetry, CRI, TM-30, chromatic adaptation, CCT, metamerism, and practical lighting citations.
• Reference, Research notes: interpretation notes for CRI limitations, metamerism risk, and lighting evaluation workflows.

• Standard illuminant mode: reads the selected illuminant from the CIE-style registry and uses its built-in spectral power distribution.
• Blackbody / Custom CCT mode: generates a Planckian spectrum from the CCT slider or numeric input. This is useful for tungsten studies, warm-to-cool comparisons, and reference source experiments.
• CCT range: the UI accepts 1500 K to 25000 K in 50 K steps.
• Link to select: when enabled, choosing a standard illuminant also syncs the CCT field to that illuminant metadata value.
• Included daylight sources: D50 for ICC and print workflows, D55 for mid-daylight studies, D65 for sRGB and common screen reference, and D75 for cooler north-sky conditions.
• Included fluorescent sources: F1-F6 approximate standard fluorescent lamps, F7-F9 approximate broadband de luxe fluorescent sources, and F10-F12 approximate narrow-band three-phosphor sources.
• Reset to D65: returns the lab to standard mode, D65, and 6500 K.

• Illuminant Summary: reports the active source label, source type, display HEX estimate, CCT, Duv, CIE x, CIE y, CRI Ra, and normalized XYZ.
• SPD chart: plots relative power from 380 nm to 780 nm in 5 nm samples. The gold trace is the active source.
• Comparison overlay: when comparison mode is enabled, the blue trace shows the selected comparison illuminant.
• Rainbow fill: the chart uses a subtle wavelength-color fill under the primary source to help orient short, middle, and long wavelength regions.
• Probe interaction: click the SPD chart to inspect the nearest wavelength and relative power value.
• Fullscreen chart: use the chart fullscreen button or double-click behavior provided by the page helper when you need a larger SPD view for review.
• Numeric caution: the on-screen white swatch is an sRGB preview of a white point and is not a calibrated measurement target.

The Lab tab draws a CRI bar chart for R1-R14 and reports Ra as the mean of R1-R8. The tool also includes TM-30 explanatory content in the Reference tab's formulas and research notes so CRI can be interpreted with its known limitations.

• CRI Ra: the general color rendering index, calculated from the first eight test color samples.
• R1-R14 bars: individual special rendering indices. R9 and saturated colors deserve separate attention because Ra can hide red or deep-color weakness.
• Reference source rule: the page notes the CRI convention of using a blackbody reference below 5000 K and a daylight reference at or above 5000 K.
• TM-30 context: the research notes explain why TM-30 uses a larger color evaluation sample set and separates fidelity from gamut behavior.
• Use CRI carefully: high Ra does not guarantee accurate saturated color rendering, especially for narrow-band fluorescent or LED-like spectra.

• Surface presets: white paint, neutral gray, saturated red, leaf green, sky blue, skin-like, yellow paint, and cyan ink.
• Toggle behavior: selected surface checkboxes appear in the Surface Appearance output. Unselected surfaces are hidden to keep the review focused.
• D65 reference: each row shows how the surface appears under D65 and under the active test illuminant.
• Delta E 2000: each surface row reports the approximate perceptual color shift after adaptation to the D65 viewing reference.
• Practical use: use the surface section to explain why two lights with similar white points can still produce different material color appearances.
• Preset limitation: the surfaces are educational reflectance curves, not measured material files. For production decisions, validate with instrument data and calibrated viewing conditions.

• Adapt from: source white point for the preview, with D65, D50, D55, D75, A, and E available.
• Adapt to: destination white point. D65 to D50 is useful for ICC and print workflows.
• Swap: reverses the adaptation pair without changing the method.
• Methods: Bradford, CAT16, CAT02, Sharp, XYZ scaling, Von Kries, and None are available. None intentionally performs no chromatic adaptation for comparison.
• 24-patch preview: the output shows original patches and adapted patches so you can see the direction and strength of the white-point transform.
• Matrix details: the matrix panel reports the active CAT matrix, LMS scaling, source white LMS, and destination white LMS.
• Keyboard shortcut: press S to swap the adaptation pair when focus is not inside an input that captures the key.

• Enable comparison: overlays a second standard illuminant on the SPD chart and opens the comparison metrics panel.
• Comparison choices: A, D50, D55, D65, D75, E, F2, F7, and F11 are exposed in the quick comparison dropdown.
• Side-by-side metrics: the comparison table reports CCT, CRI Ra, CIE x, and CIE y for the active source and comparison source.
• Metamerism index: the tool computes an average Delta E 2000 value across 14 test color sample reflectance approximations under the two illuminants.
• How to read it: low values suggest lower illuminant-metamerism risk for the sample set; high values signal that materials may shift visibly between the two lights.
• Use cases: compare D65 against A for home-lighting shifts, D50 against D65 for print-to-screen review, or F-series sources against D65 for retail and office lighting risk.

• Export SPD CSV: downloads wavelength_nm and relative_power for the active source.
• Export JSON: downloads the active illuminant label, estimated CCT, CIE xy, XYZ, CRI object, and SPD array.
• Export SPD PNG: downloads the current SPD canvas.
• Copy white HEX: copies the active white swatch HEX value to the clipboard.
• Generate share URL: encodes mode, illum or cct, and adaptation params af, at, and am.
• Copy share URL: copies the generated URL to the clipboard.
• Generate comparison table: builds a table for all 18 standard illuminants with CCT, CIE xy, CRI Ra, and white-point swatch.
• Not stored in the URL: surface checkbox selection and comparison toggle are UI state only in the current share URL model.

• Library category: Standard Illuminants is registered as a Colorimetry tool that saves spectral assets.
• Runtime state: the page exposes window.AAIlluminants.getState() and window.AAIlluminants.restoreState() for richer save and restore flows.
• Captured setup: the runtime state includes mode, illuminant, CCT, linked CCT, adaptation source, adaptation destination, adaptation model, selected surfaces, comparison illuminant, and comparison visibility.
• Generic capture: the Library binding also has a form-snapshot fallback for older illuminant selectors, so the tool remains saveable even if the full runtime API is not used by a specific capture path.
• Best practice: use share URLs for quick handoff and Library saves for workspace continuity, especially when adaptation and comparison choices matter.

• Screen reference check: choose D65, inspect the SPD and summary, then compare against D50 or A to explain screen-to-print or screen-to-home-lighting differences.
• Print viewing review: choose D50, use D65 as comparison, and inspect surface Delta E to discuss profile connection space and viewing booth behavior.
• Tungsten lighting study: choose CIE A or blackbody mode near 2856 K, then compare to D65 to show warm-source spectral imbalance.
• Fluorescent source risk: choose F2, F7, F10, F11, or F12, enable comparison against D65, and review CRI bars plus metamerism index.
• ICC adaptation note: use D65 to D50 Bradford adaptation and export or copy the share URL for handoff notes.
• Lighting QA summary: export JSON for numeric records, export PNG for visual notes, and generate the multi-illuminant table when a team needs the full source list.

• The CCT slider changes mode: moving the slider intentionally switches the lab to blackbody mode because the source becomes custom CCT driven.
• The CCT resets after picking a standard: disable Link to select if you want to keep a custom CCT value while exploring standard illuminants.
• The comparison table is blank: turn on Enable comparison in the Lab controls. The comparison panel hides metrics until that checkbox is enabled.
• The SPD chart looks flat: equal-energy E is intentionally flat, and some normalized spectra have less dramatic visible variation than narrow-band fluorescent sources.
• CRI and metamerism are approximations: the tool is educational and browser based. Use official CIE or IES tables and calibrated measurement software for compliance work.
• Clipboard actions fail: browser permissions or non-secure contexts can block clipboard writes. Use the visible export or URL field as the fallback source.
• Share URL misses a setting: the current URL stores source mode, standard illuminant or CCT, and adaptation settings. Surface and comparison selections are not currently encoded.