Linear Light combines Linear Dodge and Linear Burn and simplifies to base + 2·top − 1, decreasing contrast

Linear Light combines Linear Dodge and Linear Burn around a neutral middle grey: a lighter-than-grey blend layer dodges, a darker one burns. Its calculation simplifies to the sum of the bottom layer plus twice the top layer, minus 1. Because the underlying dodge/burn are Linear (additive) rather than Color (division-based), the tonal shift is gentler and the mode decreases contrast, unlike Vivid Light which increases it. A middle-grey blend layer leaves the base unchanged.

Examples

Linear Light of base a with blend b evaluates to a + 2b − 1 (clamped). b = 0.5 (grey): a + 1 − 1 = a, no change. b = 1 (white): a + 1, brightens/clips. b = 0 (black): a − 1, darkens/clips.

Assessment

Compute Linear Light for a = 0.6, b = 0.7 using base + 2·top − 1. Then explain why Linear Light decreases contrast where Vivid Light increases it.