Comparative Analysis of Macro and Zoom Lenses for Dental Shade Selection: An In Vitro Study

Abstract

ABSTRACT Objective This in vitro study evaluated the color accuracy and image sharpness of common macro and zoom lenses on a full‐frame body and tested whether differences among macro‐lens brands are clinically meaningful. Materials and Methods 26 VITA 3D‐Master shade tabs were each photographed three times under standardized, cross‐polarized conditions on a Nikon D610. Three macro lenses (Nikon 105 mm, Sigma 105 mm, and Tamron 90 mm) and four zoom lenses (Nikon 24–70 mm, Nikon 24–120 mm, Sigma 24–70 mm, and Nikon 24–85 mm) were compared. RAW files were converted to CIELAB; reference L*a*b* values were obtained with a 45°/0° spectroradiometer under D65. Color difference (ΔEab, CIE76) was computed for every image. Sharpness was assessed by ISO 12233 slanted‐edge SFR (MTF50) at f/16 and f/22. Linear mixed‐effects models with shade tab as a random effect were fitted; equivalence was tested with two one‐sided tests (TOST) at a prespecified ΔEab margin of 0.6. Results All macro lenses produced low, clinically acceptable color errors (mean ΔEab = 1.2; SD = 0.2) with negligible inter‐brand differences, and all macro–macro comparisons met the 0.6 equivalence margin. Zoom lenses showed significantly higher errors (mean = 2.95–3.35; SD = 0.42–0.50) and failed equivalence. Brand differences among macro lenses were non‐significant (F = 0.92, p = 0.40), whereas macro‐vs‐zoom differences were highly significant (F = 792.1, p < 0.0001); 81% of pooled zoom images exceeded the ΔEab acceptability threshold of 2.7, versus none of the macro images. MTF50 confirmed superior macro sharpness, with macro–macro differences within ±5% of the Nyquist frequency. Conclusions Dedicated macro lenses are required for accurate shade photography, with general‐purpose zoom lenses producing clinically unacceptable color errors.