Experimental Study of Transmission and Color Shift in Neutral Density (ND) Filters

Neutral Density (ND) filters attenuate irradiance uniformly across the visible spectrum while preserving color balance. We present a RAW- domain workflow to measure ND transmittance T and color shift across stops n = 1–5. Experimental transmission T exp is compared with the ideal 2−n . Color fidelity is evaluated through channel ratios (R/G, B/G) and ΔE* ab from ColorChecker targets. The optical setup, acquisition protocol, and data-reduction pipeline are described for reproducibility. We discuss polarization leakage, spectral flatness, illuminant dependence, and signal-to-noise effects. The tested filter follows 2−n closely and shows only minor, illuminant-dependent drifts near perceptibility thresholds at 5 stops.