Accuracy of linear smartphone measurements compared to a digital single lens reflex camera

Abstract Objectives The aim of this study was to compare the accuracy and reproducibility of linear measurements on photographs taken using a smartphone and a DSLR camera, using the DSLR camera as the gold standard for comparison. Materials and methods A total of 120 clinical photographs were taken of 30 participants who met the inclusion and exclusion criteria. Each participant had four standardised photographs captured: one extraoral and one intraoral view using a smartphone (Xiaomi) and repeated using a DSLR camera. Five linear measurements from the extraoral photographs and four linear measurements from the intraoral photographs were recorded. Measurements were analysed using an image software program with a precision of 0.01mm. Accuracy was assessed using the paired t-test/Wilcoxon signed ranks test while reproducibility was assessed using the paired t-test/Wilcoxon signed ranks test and ICC. Results The mean differences in measurements for the photographs captured with a DSLR camera and a smartphone were statistically significant, with the smartphone measurements consistently smaller. The reproducibility was excellent for the extraoral measurements and good to excellent for the intraoral measurements while the paired t-test showed no identified statistical differences. Conclusion Linear measurements taken from the tested android smartphone (Xiaomi Mi 10T Pro) were consistently underestimated compared to a DSLR gold standard, but intraoral discrepancies were clinically acceptable and measurement reproducibility rated good to excellent. These findings apply only to the device evaluated and should not be generalised to other smartphone models.