You view the print at an angle, and it looks to reflect light differently depending on the darkness of the ink. I had read about it years ago, but the name they gave it escapes me. Anyone know? Thanks
Gloss deferential or Bronzing depending on the what you see and the origin of this effect: https://imagescience.com.au/knowledge/bronzing-and-gloss-differential-issues-on-inkjet-papers