Drag each light to move it. To use the keyboard, select a light with Tab and use the arrow keys. Hold Shift to move faster.
Spatial illumination · synthetic LED spectra
Illustrative matte face · measured skin and color samples
Some colors exceed sRGB · Screen approximation
RGB Lab is a space to explore how colored light adds together, from ideal RGB mixing to the output of a simulated LED fixture.
Adjust Red, Green and Blue from 0 to 255, or choose a preset. Where the lights overlap, their channels add together. Full RGB produces white; all channels off produces black.
Reset restores the three intensities to 255. Basic adds display RGB values directly; it is an ideal mixing model rather than a calibrated photometric control.
Choose an LED engine and adjust its emitters: R = Red, G = Green, B = Blue, W = White, A = Amber and M = Mint. Every active emitter starts at 255; changing engines restores those full levels in Manual mode. Equal channel values do not guarantee a particular white.
For engines with White, White CCT changes only that emitter’s nominal color temperature and preserves the levels. The default is 6500 K · D65, chosen to align with the screen-white target; it is not a fixture standard.
Enter a target HEX color or select a point in the CIE xy diagram, then press Match target. Entering a target alone does not change the levels. Compare Target and Actual; a smaller Δu′v′ means closer chromaticity, not closer brightness or higher CRI. Adjusting an emitter afterwards keeps your manual mix; matching again can use every available channel.
The outer curved boundary is the physical chromaticity domain for the CIE standard observer. The green Fixture outline shows reachable chromaticities; the dashed sRGB triangle shows the preview’s color range. Background colors are approximate and the diagram does not show brightness. Outside fixture gamut means the target cannot be matched exactly. Outside sRGB means the screen preview needs approximation.
W · White supplies white light directly, adding output and making pale colors without relying entirely on an RGB recipe. In real fixtures, a phosphor-converted White LED typically emits a broader spectrum than three narrow RGB peaks. This can help illuminate colored objects more faithfully, even when both sources look equally white. Its color temperature matters: adding White does not automatically make a mix neutral, and all channels at 100% need not produce the desired white.
A · Amber adds light in the yellow–orange region, giving more control over warm whites, golds and oranges than mixing Red and Green alone. Depending on its chromaticity, it can also reach colors outside the RGB triangle; it does in these profiles. In real fixtures, its spectral contribution can help fill gaps relevant to the appearance of illuminated materials.
M · Mint is a pale greenish emitter, often with a broad phosphor-converted spectrum. It offers another way to build whites and pastels and balance green–magenta tint alongside the other channels. Here, Mint sits inside the existing gamut: its value is another mixing option and added output, rather than a larger color boundary. In a real fixture, its broader spectrum can also contribute to color rendering.
CRI (Color Rendering Index) describes how faithfully a nominally white source renders test colors compared with a reference at a similar color temperature. Two lights can have the same white chromaticity yet make skin, fabrics or scenery look different because their spectra differ. Adding W, A or M does not guarantee a higher CRI: the actual emitters and their mix matter.
Choose Surfaces and drag the beams directly over the fixture face and color samples. Only the areas reached by a beam are illuminated; overlapping beams add their light. Blur softens the light’s falloff. The background shows a faint footprint to locate each beam. The D65 reference stays uniformly illuminated in a corner PIP. The main face fills the visual area, with the material samples below it.
Fixture and Surfaces share the engine, emitter levels, beam positions and blur. Match reference white calculates a recipe for the combined light; overlap the beams on a surface to inspect it. Partial overlaps create different local mixtures. Exposure stays fixed: dimming a channel or moving its beam away makes that area darker. The comparison does not automatically equalize local brightness or white-balance the surfaces.
The face is an illustrative matte shape using a measured skin reflectance, not a photograph of the measured person. Choose among three measured skin samples. The colored samples use measured spectral data; Gray is an ideal 18% reflector. Object brightness is preserved: each sample is not separately brightened or white-balanced.
The LED spectra are synthetic examples fitted to our nominal emitter chromaticities, not measurements of real products. They show how spectra can affect reflected colors, but cannot predict a commercial fixture’s performance. RGB Lab does not calculate CRI. More channels offer more choices, not an automatic improvement in every mix.
Surface data: NIST · skin reflectance, CIE · color samples, CIE · D65. CIE-derived data: CC BY-SA 4.0.
Further reading: ETC · additional emitters, ETC · Mint and White, US DOE · color and CRI (PDF).
Hover over the lights to see the outline and name of the emitter that will be selected, then drag to move it. In overlaps, the nearest eligible light center is selected. The hint disappears while dragging. With the keyboard, use Tab to select a light and the arrow keys to move it by 5 px, or 20 px with Shift.
Blur softens the edges, starts at 20 px and ranges from 0 to 80 px. Reset positions restores the layout without changing intensities or blur.
This browser remembers the last selected mode before the next visit. Only the mode is saved; levels, positions, blur, engine, White CCT and skin return to their defaults on reload. The app uses localStorage for this preference and has no account or analytics. Its fonts and data are bundled locally.
Fixture profiles are generic approximations, not measurements of real products. Preview HEX is a screen representation; xy and Δu′v′ describe the calculated light. The swatches show combined emitter output, while the canvas shows their spatial overlap at a fixed exposure.
Application code: MIT. Data and font licenses remain separate. Licenses and attribution.