Every stop is the same stop.

Exposure is one quantity written in four currencies — aperture, shutter, sensitivity and filter — and they trade exactly. A stop of aperture is a stop of ISO is a stop of ND. So a look is not something you choose; it is something you pay for, and the bill is arithmetic rather than opinion. The consequence nobody budgets for: the frame rate is an exposure decision. Shutter time is the angle over 360 times the rate, so holding the 180° shutter and doubling the rate is exactly one stop, every time. 120 fps is 2.3 stops darker than 24 with nothing about the lighting different.

The engine is free and needs no account. Write the light level and the setups, and every exposure comes back as an error in stops — with the three ways to pay it priced, because each one spends something different and one of them runs out: a frame has 360° in it and no more, so a shortfall over one stop cannot be paid at the shutter at all. It reads all three neutral-density scales and says which one it read, because ND 0.9, ND8 and three stops are one piece of glass and reading the 8 as stops is five stops wrong. And it checks the shutter against the mains — but only where mains lighting is actually doing the work, because the sun does not pulse. Every lane ships a worked example that costs nothing. Writing the report needs credits.