밝다(bak-da, bakda)
Indicates a state with lots of light or a bright, positive mood.
When to use
Well-lit place, Cheerful personality, Positive atmosphere
The nuance
Use 밝다 when there is sufficient light or when describing a cheerful, positive personality or atmosphere.
어둡다(eo-dup-da, eodupda)
Indicates a lack of light or a gloomy, dark atmosphere or mood.
When to use
Dimly lit place, Gloomy mood, Somber atmosphere
The nuance
Use 어둡다 when there is insufficient light or when describing a gloomy mood or dim, somber atmosphere.