I once read that the Book of Kells has a feature that can usually not or only under ideal circumstances be observed on a digital reproduction or photo: Some nar

I once read that the Book of Kells has a feature that can usually not or only under ideal circumstances be observed on a digital reproduction or photo: Some narrow lines of the drawings produce optical illusions when seen from a typical reading distance. It is supposed to be a kind of "virtual" glowing colours between the lines that seem to disappear when you focus on them. -- Can anyone here confirm this?