Digital & Electronic Forensic Service, Metropolitan Police Service, 40-42 Newlands, Sydenham, London SE26 5NF, UK.
Forensic Sci Int. 2011 Oct 10;212(1-3):231-7. doi: 10.1016/j.forsciint.2011.06.023. Epub 2011 Jul 28.
Photoanthropometry is a metric based facial image comparison technique. Measurements of the face are taken from an image using predetermined facial landmarks. Measurements are then converted to proportionality indices (PIs) and compared to PIs from another facial image. Photoanthropometry has been presented as a facial image comparison technique in UK courts for over 15 years. It is generally accepted that extrinsic factors (e.g. orientation of the head, camera angle and distance from the camera) can cause discrepancies in anthropometric measurements of the face from photographs. However there has been limited empirical research into quantifying the influence of such variables. The aim of this study was to determine the reliability of photoanthropometric measurements between different images of the same individual taken with different angulations of the camera. The study examined the facial measurements of 25 individuals from high resolution photographs, taken at different horizontal and vertical camera angles in a controlled environment. Results show that the degree of variability in facial measurements of the same individual due to variations in camera angle can be as great as the variability of facial measurements between different individuals. Results suggest that photoanthropometric facial comparison, as it is currently practiced, is unsuitable for elimination purposes. Preliminary investigations into the effects of distance from camera and image resolution in poor quality images suggest that such images are not an accurate representation of an individuals face, however further work is required.
人像测量学是一种基于面部图像的度量比较技术。通过使用预定的面部地标，从图像中获取面部的测量值。然后，这些测量值被转换为比例指数 (PI)，并与另一个面部图像的 PI 进行比较。人像测量学在英国法庭作为一种面部图像比较技术已经使用了超过 15 年。人们普遍认为，外在因素（例如头部的方向、相机角度和与相机的距离）会导致照片中面部的人体测量值出现差异。然而，对于量化这些变量的影响的实证研究有限。本研究的目的是确定在不同角度拍摄的同一人的不同图像之间的人像测量值的可靠性。该研究检查了 25 名个体的面部测量值，这些个体的照片是在受控环境中从不同的水平和垂直相机角度拍摄的。结果表明，由于相机角度的变化，同一个体的面部测量值的可变性可能与不同个体之间的面部测量值的可变性一样大。结果表明，目前所实践的人像测量学面部比较不适合作为鉴别目的。初步研究了相机距离和图像分辨率在低质量图像中的影响，表明这些图像不能准确代表个体的面部，但是需要进一步的工作。
