Interesting factoids:
445.9nm is the peak in the CIE "z_bar" color matching function used to weight a spectral distribution to calculate the Z term, from which the x, y, and z chromaticity coordinates are computed via the formulae:
x = X/(X+Y+Z), y = Y/(X+Y+Z), z = Z/(X+Y+Z)
If Z is larger, then the (x,y) pair moves more toward the deep violet corner of the x,y color space. But because the effect depends not only on the fact that Z is in the denominator but also that as the wavelength moves from 473nm -> 445nm, the "blue impact" value of 445nm is 1.56 times greater than 473nm in affecting how deep into the violet corner the resulting gamut extends.
There are also revised luminous efficiency functions, such as the
Sharpe, Stockman, J., & J. 2005 revised V*_lambda function, which has the relative brightness of 473nm vs. 445nm at only 2.51, vs. 3.45 for the CIE 1924 V_lambda function.
The point is that much deeper blues can be produced from 445nm vs. 473nm, for a given power, than is suggested by their relative luminosities. Second, there is unresolved debate about the luminosity functions, and 445nm might not be as much dimmer than 473nm than indicated by the V_lambda function to which most commonly refer.
Extensive data on the functions may be found here:
http://cvrl.ioo.ucl.ac.uk/