Optical Density vs Contrast Ratio: What 10:1 and 4:1 Really Mean
Optical density and contrast ratio describe the same thing, linked by one equation: contrast ratio = 10^(ΔOD). This article shows how to convert between them, why 10:1 = OD 1.0 and 4:1 ≈ OD 0.6, and why opaque chrome (OD 3 ≈ 1000:1) can never be a low-contrast target.