Figure 3.

A schematic view of how a single VPC trial would be carried out using the current model. The two test faces can each be compared to the original sample, leading to two difference images labeled here as Δ_intra and Δ_extra. Both of these can be analyzed using the intra-and extra-personal subspaces to determine the probability that each one represents extra-personal variation. Ideally, the true extra-personal difference image will have a larger posterior probability than the intra-personal difference.