Question 1

What are the main light measurement units?

Accepted Answer

Luminous flux: lumens (total light). Luminous intensity: candela (directional). Illuminance: lux or foot-candles (light on surface). Luminance: cd/m² or nits (surface brightness).

Question 2

How do I choose the right light bulb?

Accepted Answer

Match lumens to brightness needed (800 lm ≈ 60W incandescent). Choose color temperature for ambiance. Check CRI (90+ for accurate colors). Consider beam angle for spotlights.

Question 3

What's the difference between lumens and lux?

Accepted Answer

Lumens measure total light output from a source. Lux measures light arriving at a surface. Same lumens in a smaller area = higher lux.

Question 4

How do I convert old wattage to lumens?

Accepted Answer

Roughly: 40W incandescent ≈ 450 lumens, 60W ≈ 800 lumens, 100W ≈ 1600 lumens. LED equivalents use 80-90% less power for same lumens.

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