Date: May 2024.
Source: Orthodontics and Craniofacial Research; 00:1-10. doi:10.1111/ocr.12808.
Objective: In addition to studying facial anatomy, stereophotogrammetry is an efficient diagnostic tool for assessing facial expressions through 3D video recordings. Current technology produces high-quality recordings but also generates extremely excessive data. Here, we compare various recording speeds for three standardized movements using the 3dMDface camera system, to assess its accuracy and reliability.
Materials and Methods: A linear and two circular movements were performed using a 3D-printed cube mounted on a robotic arm. All movements were recorded initially at 60 fps (frames/second) and then at 30 and 15 fps. Recording accuracy was tested with best-fit superimpositions of consecutive frames of the 3D cube and calculation of the Mean Absolute Distance (MAD). The reliability of the recordings were tested with evaluation of the inter- and intra-examiner error.
Results: The accuracy of movement recordings was excellent at all speeds (60, 30 and 15 fps), with variability in MAD values consistently being less than 1 mm. The reliability of the camera recordings was excellent at all recording speeds.
Conclusions: This study demonstrated that 3D recordings of facial expressions can be performed at 30 or even at 15 fps without significant loss of information. This considerably reduces the amount of produced data facilitating further processing and analyses.

3dMD correction for Section 2.2 | 4D camera system: The tested camera system was a four-dimensional camera system that projects an unstructured white-light speckle pattern on the subject to support the stereophotogrammetry-based software technique that reconstructs the three-dimensional pictures or progressive sequences of 3D surface images (60Hz 3dMDface.u, 2017 model, 3dMD, Atlanta, GA, USA). The system consists of two modular camera units (MCUs) synchronized with a robust LED lighting system. Each unit consists of three 1.3 mega pixel machine vision cameras (two greyscale and one colour one) and one white-light speckle projector unit. The 4D camera system allows for individual 3D photo acquisition and progressive 3D image sequence recordings at various speeds between 1 and 60 frames/second (fps).

Article: Three-dimensional video recordings: Accuracy, reliability, clinical and research guidelines – Reliability assessment of a 4D camera.
Authors: Gabriella Coppola, Dominik Hänggi, Gianluca Cassina, Carlalberta Verna, Nikolaos Gkantidis, Georgios Kanavakis, Department of Pediatric Oral Health and Orthodontics, University Center for Dental Medicine Basel UZB, University of Basel, Basel, Switzerland.