Kelvin white, can it be white?

Help and Troubleshooting
1

What I’m not understanding is why the default light starts out as FFFFF and 6502K but as soon as you nudge the color, it won’t go white anymore. It feels like the default light is white, but the way Kelvin is converting won’t allow it. So if I have a light set to 6502 (still not sure why it isn’t 6500 either) and showing FFFFFF. Will it render as FFFFF or BEBABF?

(I’m not using any color transforms in the image tab, and white balance is set to 0)

2

@andy.engelkemier.2 Hi Andy,

I’m 99% sure the HEX #FFFFFF is a practical hack by the devs to simulate pure white. Physically accurate color temperatures can’t produce pure white, so this is likely a workaround. I’m speculating, but I believe the 6502K value isn’t meant to represent the actual white swatch. It probably acts as a threshold to suppress visible hue.

Kelvin color temperature comes from blackbody radiation, which never emits equal energy across the RGB spectrum. Even at 6500K (D65), there’s more blue than red. That tint reads as daylight to the human eye, but it’s not mathematically neutral. Our brain compensates using its built-in white balance system. This is known as psychovisual normalization.

Hex codes are not spectral data. They’re just visual approximations, only valid within the assumptions of a given color space.

Short Answer:

  1. #FFFFFF is an sRGB encoding of pure white. It has no direct correlation to any Kelvin temperature.
  2. Physically accurate color temperatures can never produce pure white. Blackbody emitters always carry spectral bias.
  3. #BFBABF is an approximate sRGB mapping of blackbody radiation in the ~6500K to 6578K range. The slight blueish-magenta tint is physically accurate.
  4. Yes, even small changes in color temperature will subtly affect material appearance in physically based renders. If you need true white, use a different color source or manually override with neutral RGB values.
  5. Kelvin values are physical approximations. They do not map linearly or precisely into color spaces like sRGB or HSV. All mappings rely on empirical curves or lookup tables.

For precision-critical workflows, especially in rendering pipelines, color temperature should always be viewed as a spectral intent. It is never an exact RGB output. Gamma curves, tone mapping, and color space transformations all introduce nonlinear effects.