Remember we said earlier that the Eigenfaces and Fisherfaces algorithms are based on the notion that an image can be roughly represented as a set of eigenvectors (special face images) and eigenvalues (blending ratios). So if we combine all the eigenvectors with the eigenvalues from one of the faces in the training set then we should obtain a fairly close replica of that original training image. The same applies with other images that are similar to the training set—if we combine the trained eigenvectors with the eigenvalues from a similar test image, we should be able to reconstruct an image that is somewhat a replica to the test image.