The blue hour (from French l'heure bleue) is a period of twilight in the morning and in the evening, during the civil and nautical twilight phases, when the sun is at a significant depth below the horizon and when the residual, indirect sunlight takes on a predominantly blue shade. On a clear day, blue hour can be a colorful spectacle, with the indirect sunlight tinting the sky yellow, orange, red, and blue. This effect is caused by the relative diffusibility of short blue wavelengths of light versus the longer red wavelengths. During the blue "hour" (typically a period about 20 minutes in length), red light passes straight into space, while blue light is scattered in the atmosphere, so reaches Earth's surface. Many artists treasure this period because of the quality of the light. Although the blue hour does not have an official definition, the blue color spectrum is most prominent when the sun is between 4 and 8° below the horizon.
Video Blue hour
See also
- Summer Evening on Skagen's Southern Beach
- Belt of Venus
- Civil twilight
- Golden hour
- Green flash
- Midnight sun
- Polar night
Maps Blue hour
Notes
References
External links
- Blue hour mobile application (iOS, Iphone/iPad)
- bluehoursite.com: Everything about Blue Hour and Night Photography (news, articles, tips and calculator)
- Twilight Calculator, Golden Hour/Blue Hour table
Source of article : Wikipedia
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