same frame rate, same T and ISO, change only shutter angle → exact stops, cine ND0.3 notation, and a practical filter stack
Light varies with effective shutter time t = (angle/360) / fps. This tells you how much ND to add or remove so the last take at one angle can match a new angle without re-balancing the scene with iris or gain.
t₁ = 0.0208 s (1/48 s) → t₂ = 0.0104 s (1/96 s) · Δ light -1.00 stops (log₂ t₂/t₁)