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

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.

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.

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.

Dedicated macro lenses are required for accurate shade photography, with general-purpose zoom lenses producing clinically unacceptable color errors.