Contrast ratio is the brightness difference between the brightest white and darkest black a display can show, expressed as a ratio (e.g., 1000:1). Higher ratio = deeper blacks, more vivid image.
Contrast ratio definition: peak white luminance ÷ peak black luminance.
Examples: LCD with 300 nits max and 0.3 nits black: 300 ÷ 0.3 = 1000:1 ratio. OLED with 2000 nits peak and 0 nits black (pixel off): infinite (∞:1) ratio.
Ratio tiers: 300:1: typical budget LCD, acceptable for everyday. 1000:1: standard office monitor, good for content work. 5000:1: premium LCD (gaming monitor with deep blacks). ∞:1 (infinite): OLED (perfect black, pixel turns off completely).
Perceptual impact: human eye perceives contrast logarithmically. Jump from 100:1 to 1000:1 is dramatic; jump from 1000:1 to 10000:1 less dramatic.
OLED superiority: OLED's infinite contrast is the primary reason it looks punchier than LCD. A scene with stars on black background shows individual stars clearly on OLED; on LCD, stars get "washed out" by backlight glow on black.
Measurement nuance: contrast ratio varies by test method. Some manufacturers measure only center pixel; professional reviews measure uniform area. RTINGS and similar sites standardize methodology.
When it matters: movies/TV viewing (infinite contrast improves cinematics), photo editing (easier to judge tones), gaming (shadows clearer with deeper blacks). Web browsing/email: barely noticeable difference.
Monitor shopping: if choosing between budget LCD (1000:1) and gaming LCD (5000:1), the gaming choice looks noticeably better. OLED vs any LCD: OLED contrast wins decisively.