Transmitted light: 100%
3
How stacking angled filters can block light — or bring it back
A polarizing filter only lets through light oscillating along its own transmission axis. Stack several filters at different angles and something surprising happens: two filters crossed at 90° block almost all the light, yet inserting a third filter in between — at just the right angle — lets a good chunk of the light back through. Set the number of layers and the angle of each one below and watch the effect play out on the image, following Malus's law exactly.
A polarizing filter isn't a shutter that simply blocks or passes light. It splits any incoming light into two perpendicular components — one aligned with its own transmission axis, one at 90° to it — and lets only the aligned component through, absorbing the rest. If the light's polarization sits at angle Δθ from that axis, the transmitted fraction is cos²(Δθ) (Malus's law). Light that has just passed a filter emerges fully aligned with that filter's axis, so the next filter measures its own Δθ from there — not from some fixed zero.
That's why two crossed filters (Δθ=90°) block almost everything: cos²(90°)=0. But insert a third filter at 45° between them, and the light gets decomposed twice instead of once — each 45° step only costs a cos²(45°)=50% loss, letting about 12.5% back through. Try the Three-filter reveal preset, then compare it with Gentle rotation, which spreads the same 0°→90° turn over five small steps and lets even more light through.