Analysing Texture in Portraits

Abstract

This case study is an initial exploration as to whether the depiction of texture in a set of portraits, all portraying the same Sitter, is related to the familiar likeness assessments reported in a companion paper containing a principal component analysis (PCA) of the portraits’ depiction of shape. Somewhat unexpectedly, a texture PCA failed to discriminate the high from low likeness portraits, despite experimentation with different pre-processing methods to reduce the portraits’ high level of uninformative, image-level texture variability. There were some findings arising from these analyses, and while only indicative at this stage, include that linear histogram matching is effective in reducing variability in portrait brightness; that depicting, and perhaps exaggerating, shading relating to lighting direction may enhance portrait likeness; and, that whether minimised or exaggerated, lighting direction can be portrayed somewhat anomalously. Furthermore, and in agreement with findings from photographs, shape and texture were not found to be independent variables, and shape-free image registration, while very usefully enabling a comparison of closely corresponding pixel coordinate values, could itself be a confounding factor for undertaking a texture PCA with portraits produced under relatively ambient conditions.

Not the norm: Face likeness is not the same as similarity to familiar face prototypes.

“…Likeness may not just be about capturing what you look like on average, but also about what makes you look different from other people. Indeed, Hayes et al (2020) reported that familiar observers tended to emphasize facial distinctiveness over face typicality when assessing the likeness of portraits and that lower morphological accuracy was related to higher likeness ratings (Hayes et al, 2018). These results suggest that likeness is unlikely to simply be a proxy for prototypicality, but to our knowledge this has not yet been directly assessed.…”

Not the norm: Face likeness is not the same as similarity to familiar face prototypes

“…The likeness may not just be about capturing what you look like on average but also about what makes you look different from other people. Indeed, Hayes. (2020) reported that familiar observers tended to emphasize facial distinctiveness over face typicality when assessing the likeness of portraits and that lower morphological accuracy was related to higher likeness ratings (Hayes et al, 2018).…”