Ratio Lab
Every book says “light your portrait 3:1.” Here you can see it. Drag the fill and watch the key-to-fill ratio move in stops — measured in linear light from the two cheek patches, not from the slider.
Key
Fill
Read the ratio
- The ratio is key-cheek luminance ÷ fill-cheek luminance, in linear light.
- Each stop doubles the difference: 2:1 = 1 stop, 3:1 ≈ 1.6, 4:1 = 2 stops.
- Push fill to zero and the shadow crushes — the number stops being honest, and says so.