Fig. 3

Pseudocolour renderings of (from left) phantoms with crosses in: iron gall ink; carbon ink; red iron oxide and India ink following principal component analysis. The analysis was intended to maximise contrast of the deepest crosses
Pseudocolour renderings of (from left) phantoms with crosses in: iron gall ink; carbon ink; red iron oxide and India ink following principal component analysis. The analysis was intended to maximise contrast of the deepest crosses