CIE Plot
The CIE Plot visualises the chromaticity of the signal on the CIE chromaticity diagram — the horseshoe-shaped footprint of all colours visible to an average human observer. Each triangle drawn on top of it is the gamut of a colour space, defined by its three primaries and a white point. Pixels from your image are plotted as dots inside the horseshoe so you can see, at a glance, how much of the target gamut the image actually uses and whether any pixels spill outside it.
The CIE diagram is built from the CIE 1931 Standard Observer — colour-matching functions derived from Wright and Guild's 1928–29 experiments (17 subjects matching reference lights through a small foveal field of view). The outer horseshoe boundary is the spectral locus: the position of every pure monochromatic wavelength from ~380 nm (violet) to ~700 nm (red). The straight bottom edge is the line of purples, which closes the locus between violet and red — purples don't exist as single wavelengths, they're always mixtures.
Supported Gamuts
CIE Plot overlays the following gamut triangles:
Rec. 709
HD broadcast / consumer sRGB (same primaries)
Rec. 2020
UHD container, wider than any current mastering display
P3
DCI-P3 theatrical and P3-D65 consumer HDR
ACES AP0
Largest gamut in production use — encloses all visible colours (primaries outside the spectral locus)
ACES AP1
ACEScg working space — tighter than AP0, still wider than Rec. 2020
ProPhoto
ROMM RGB — wide, print-oriented still-photography gamut
Adobe RGB
~Rec. 709 + a wider cyan/green region, common in photo pipelines
White Points
Gamut triangles are anchored to a white point — the chromaticity the display renders when R = G = B:
D65
0.3127, 0.3290
Rec. 709, Rec. 2020, sRGB, P3-D65 (consumer HDR)
D60
0.32168, 0.33767
ACES default, some reference projection
DCI
0.3140, 0.3510
DCI-P3 theatrical ("P3-DCI") — greener than D65
D65 is a CIE Daylight illuminant approximating average noon daylight at ~6504 K. D60 and DCI sit close on the Planckian locus but at different correlated colour temperatures.
Blackbody (Planckian) Curve
Enable Blackbody temp curve to overlay the Planckian locus — the chromaticity trajectory of an ideal blackbody radiator as its temperature changes. This is the curve that correlated colour temperature (CCT) references; a "5500 K daylight" light lies on or near this locus. Useful for verifying white-balance decisions and for seeing how far your image's average chromaticity drifts from a neutral daylight reference.
Gamut Error Check
In HDR workflows, when monitoring a Rec. 2020 signal, you can flag pixels that fall outside P3 by enabling Gamut Error Check. P3 is the realistic chromaticity target for today's mastering and consumer HDR displays, even when the signal is carried inside the wider Rec. 2020 container.
Out-of-gamut pixels are rendered with an inverted colour (yellow pixels above the P3 triangle instead of blue) so they visually separate from in-gamut energy.
Custom Primaries
Custom primaries can be defined in the scope settings for non-standard gamuts (camera native spaces, vendor-specific working spaces, etc.):
Coordinate Systems
CIE 1931 xy is the historical default — the diagram most colourists recognise. Its horseshoe is not perceptually uniform: small distances in the green region correspond to much larger perceived colour differences than equivalent distances in the red or blue regions. This is the famous "MacAdam ellipses" problem — ellipses of just-noticeable-difference are tiny in blue/purple and huge in green.
CIE 1976 u'v' (u' = 4X/(X+15Y+3Z), v' = 9Y/(X+15Y+3Z)) is available in 1.11.25+ and is more perceptually uniform — the just-noticeable-difference ellipses become closer to uniform circles across the diagram. This makes visual comparisons of gamut coverage more honest. u'v' is also the coordinate system underlying modern colour-difference metrics like ΔE in CIE Lab/Luv.
Switch to u'v' when you want an honest visual sense of how much "extra colour volume" a wider gamut actually gives you; stay on 1931 xy when you need to match the diagrams in classic textbooks and specifications.
What's plotted, and what's discarded
The chromaticity plot discards luminance. A dim red pixel and a bright red pixel of the same chromaticity land on the same spot. Brightness is handled by the waveform and HDR Limit tools; the CIE Plot is purely about which colours are present, not how bright they are. That's why the CIE Plot is so valuable alongside a waveform — together they describe both the position in chromaticity and the position in light of every pixel.
Directional Indicators (1.11.22+)
Directional indicators can be enabled to show drift direction relative to the target gamut — useful when gamut-mapping decisions need to know whether out-of-gamut energy is pushing toward greens, reds, or elsewhere.
Related
Gamut Scope — false-colour gamut-error overlay on the source image
Gamut Check — QC rule variant
Last updated