Question 1

What is luminance and why does it matter?

Accepted Answer

Luminance (cd/m² or nits) measures how bright a surface appears to the eye. Monitors: 250-400 nits. Phone screens: 500-1000 nits. HDR displays: 1000+ nits.

Question 2

How do I convert between luminance units?

Accepted Answer

1 cd/m² = 1 nit. 1 foot-lambert = 3.426 cd/m². 1 lambert = 3183 cd/m². 1 apostilb = 0.318 cd/m².

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.

Light Unit Converter - Free Online Tool

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