color flop
Flop Index is the measurement on the change in reflectance of a metallic color as it is rotated through the range of viewing angles. A flop index of 0 indicates a solid color, while a very high flop metallic or pearlescent basecoat/clearcoat color may have a flop index of 15-17.
https://www.xrite.com/service-support/definition_of_flop_index
FI(Flop Index)最早由杜邦公司提出，可以翻译为动态指数，或转向指数，该指数越高，随角异色效果越明显，也被称为变色龙效果