HOW THIS LAB WORKS

MOVE HER — drag the subject along the floor, or use ‹ › / the arrow keys. Shift+arrow jumps a full ring. Every ring is two stops of light lost or gained — 1 m is your starting point, right by the light, with only 0.5 m closer and 2 m/4 m/8 m/16 m to retreat through.

THE RINGS — the doubling ladder: 0.5, 1, 2, 4, 8, 16 m (a guide number of 8), evenly spaced in LIGHT, each ring exactly two stops from its neighbor. The math keeps going past f/1 — f/0.7, then f/0.5 at 16 m — but no real lens opens that wide. Past f/1, the ladder is still there on paper; the camera just can't save you anymore. The dotted rings at 3, 6, 12 m are the in-between doublings — also two stops apart — landing near, but not exactly on, standard stops. The ½ STEPS toggle hides them and skips them when stepping.

AUTO vs M on the f-ring — AUTO re-opens the aperture to hold exposure constant as she walks; M locks one f-stop so you watch the frame actually go dark.

GRID drops a 1×1 m frame at her plane — at 1 m it's a single tile; beyond that n = round(d) tiles per side (2 m tiles it 2×2, 4 m tiles it 4×4, 8 m 8×8, 16 m 16×16), each square getting 1/n² of the light. That's the butter-on-toast version of 1/d². Under sunlight the patch stops growing and dimming entirely — real sun doesn't fall off over a few metres.

INFO panel explains the guide number: the inverse-square law turns into a constant (f-number × distance = GN). Real flashes print theirs on the box.

SUN swaps the softbox for real sunlight, 149.6 million km away. Distance stops mattering — walking a few metres is nothing against that scale, so exposure stays flat no matter where she stands. The tag above her reads f/16 at every ring — Sunny 16 made literal: the same exposure everywhere.

ACT 2 · THE FALLOFF — now the light moves, not her. Drag the rig or use ‹ › to step it half a metre at a time (0.5 → 6 m); DRAMA and CATALOG jump to two presets showing how close light separates three people and far light flattens them together. INFO opens the ratio explanation, and the little i beside SPREAD and BACKDROP explains what each number measures.