The common assumption is that higher the colour temperture (I have written about Colour temperature in another blog) the “brighter” the light… This assumption is not all together correct.
Brightness is a function of intensity more than what it looks like. Intensity can be measured with a light meter much like a camera does to ensure correct exposure.
Remember photographic film?
Too much exposure and the film would “burn out” and there would be no image… reduce the intensity – “stop down” the lens… success!… And in low light we would need a flash because it wasnt bright enough!
We have lost this understanding more and more as cameras became able to think for themselves even before going digital. Even so, most of the cameras on mobile phones struggle in low light situations
Raising the colour temperature toward the blue end of the spectrum might appear to be increasing brightness to us. In fact we are seeing another effect… starkness! Less red in the light, more blue and what we see seems bright but it isnt. Warm tones will go flat… will appear to be bleached as we might expect with film technology but we are seeing a lack of colour – not too much light. We are being fooled, much like by a magician.