3
votes
2answers
600 views

Is light brightness subjective or can it be quantified?

What is the relationship between brightness perception and physical properties of light, such as light intensity?
2
votes
5answers
2k views

Eye sensitivity & Danger signal

Why are danger signal in red, when the eye is most sensitive to yellow-green? You can check luminosity function for more details...
3
votes
1answer
50 views

How do you transform between theoretical Hertzsprung-Russell Diagrams and Colour-Magnitude Diagrams?

When discussing stars, theorists tend to use effective temperature $T_\text{eff}$ and luminosity $L$ (on logarithmic scales). Observers, on the other hand, usually talk about observed colours and ...
1
vote
3answers
3k views

Why is moonlight less colourful than yellow light?

Just what the title states; and this isn't an original question ... On full-moon, moonlight is almost as bright as mid-dawn ; yet there is hardly any colour visible. This is not the case with ...