function [w1,w2] = CIE_daylight_weights(T)

% Usage: [w1,w2] = CIE_daylight_weights(T)
% Caluculates weight factors for CIE daylight eigenvectors S1 and S2 
% according to CIE Publication 15.2 (?)
% T should be between 4000 K and 25000 K!
% T may be a vector.

low_T_idx = find(T < 7000);
high_T_idx = find(T >= 7000);

% Chromaticity coordinates x and y:
x = zeros(size(T));
x(low_T_idx) = -4.6070*(10^9./T(low_T_idx).^3) + 2.9678*(10^6./T(low_T_idx).^2) + 0.09911*(10^3./T(low_T_idx)) + 0.244063;
x(high_T_idx) = -2.0064*(10^9./T(high_T_idx).^3) + 1.9018*(10^6./T(high_T_idx).^2) + 0.24748*(10^3./T(high_T_idx)) + 0.237040;
y = -3.000*(x.^2) + 2.870*x - 0.275;

% Weights:
w1 = (-1.3515 - 1.7703*x + 5.9114*y)./(0.0241+ 0.2562*x - 0.7341*y);
w2 = (0.0300 - 31.4424*x + 30.0717*y)./(0.0241 + 0.2562*x - 0.7341*y);