FacialSCDnet: A deep learning approach for the estimation of subject-to-camera distance in facial photographs Bermejo, Enrique Photography Human identification Transfer learning Perspective distortion Subject-to-camera distance Facial biometrics play an essential role in the fields of law enforcement and forensic sciences. When comparing facial traits for human identification in photographs or videos, the analysis must account for several factors that impair the application of common identification techniques, such as illumination, pose, or expression. In particular, facial attributes can drastically change depending on the distance between the subject and the camera at the time of the picture. This effect is known as perspective distortion, which can severely affect the outcome of the comparative analysis. Hence, knowing the subject-to-camera distance of the original scene where the photograph was taken can help determine the degree of distortion, improve the accuracy of computer-aided recognition tools, and increase the reliability of human identification and further analyses. In this paper, we propose a deep learning approach to estimate the subject-to-camera distance of facial photographs: FacialSCDnet. Furthermore, we introduce a novel evaluation metric designed to guide the learning process, based on changes in facial distortion at different distances. To validate our proposal, we collected a novel dataset of facial photographs taken at several distances using both synthetic and real data. Our approach is fully automatic and can provide a numerical distance estimation for up to six meters, beyond which changes in facial distortion are not significant. The proposed method achieves an accurate estimation, with an average error below 6 cm of subject-to-camera distance for facial photographs in any frontal or lateral head pose, robust to facial hair, glasses, and partial occlusion. 2022-09-05T10:34:47Z 2022-09-05T10:34:47Z 2022-12-30 journal article Enrique Bermejo, Enrique Fernandez-Blanco, Andrea Valsecchi, Pablo Mesejo, Oscar Ibáñez, Kazuhiko Imaizumi, FacialSCDnet: A deep learning approach for the estimation of subject-to-camera distance in facial photographs, Expert Systems with Applications, Volume 210, 2022, 118457, ISSN 0957-4174, https://doi.org/10.1016/j.eswa.2022.118457. http://hdl.handle.net/10481/76521 https://doi.org/10.1016/j.eswa.2022.118457 eng http://creativecommons.org/licenses/by-nc-nd/4.0/ open access Attribution-NonCommercial-NoDerivatives 4.0 Internacional