Zone System Reference
Ansel Adams' Zone System divides tonal range into 11 zones (0–X) from pure black to pure white. Each zone represents one stop of exposure. Zone V is middle grey — 18% reflectance.
The Exposure Rule: Meter a mid-tone (Zone V), then place it where you want it by adjusting exposure. Moving exposure +1 EV moves your metered tone up one zone. Moving -1 EV moves it down one zone.
The Development Rule: "Expose for the shadows, develop for the highlights." N+1 development expands contrast (raises highlights). N-1 compresses it (lowers highlights). The shadows remain where you placed them.
The Development Rule: "Expose for the shadows, develop for the highlights." N+1 development expands contrast (raises highlights). N-1 compresses it (lowers highlights). The shadows remain where you placed them.