Luminance range in HALF

Hi experts,

I have a question about the luminance range in EXR HALF format. As I
understand, the luminance range of human vision is from 10 ^ -6 to 10
^ 8 cd/m^2. However, the range of HALF is around 10 ^ -3 to 10 ^ 5
(positive), which cannot cover the whole real luminance range. How
does EXR deal with this issue? Any references I could look up?

Cheers,

Jack