There isn’t a single Kelvin cutoff. Human color adaptation depends on both color temperature and brightness.

In bright conditions (photopic vision, cone-dominated), our visual system adapts well across a broad range. The Kruithof curve is often cited here: at daylight-like brightness, roughly 4500K and above can look natural, while at lower light levels much warmer illumination also feels natural.

As light levels fall, vision shifts from photopic to mesopic and then scotopic. In mesopic/scotopic vision, rods contribute more, color discrimination drops, reds fade, and overall color perception becomes less reliable. So “white balance” by human vision becomes weaker in dim light regardless of Kelvin.

Very cool light—around 7000–8000K and higher—often starts to look unnaturally blue unless you’ve adapted to it. Likewise, under very warm light such as candlelight, your brain may partially normalize the scene, but color information is limited, so many colors won’t be judged accurately even if the scene feels subjectively normal.

So the practical answer is: adaptation is strong but incomplete, and it is governed by both illumination level and spectrum, not just Kelvin.