Why is dispersion value inverted?

[LudvikKoutny]

Hi,

a simple question, as the thread title says. Is there any technical/physics related reason Abbe. parameter in VrayMTL is inverted (lower values produce stronger dispersion)? Or did someone just have a bad day and decided to make this feature a bit more counter-intuitive to use?

[svetlozar.draganov]

This is how the parameter is calculated in Physics - the lower the Abbe value, the greater the dispersion of light.

[LudvikKoutny]

Oh, yes! Just found it on wikipedia. Now it makes sense, thanks!