When you see a strong blue tone to photographs, it could be that the photographer has taken advantage of the blue hour. That’s a time of day when the sun has just set or is about to rise, when the sky overhead takes on a deep blue color, and when the landscape is suffused with bluish light. The blue hour is a good time to take photos of the moon, because then the moon’s glare isn’t so bright in contrast to the sky. It’s also a good time to take landscape photos, as the photos on this page show. Photography.about.com says:
The blue hour … doesn’t even come close to lasting a full hour. In reality, what photographers call the blue hour really only lasts about 20 minutes. The blue hour generally lasts the 20 to 30 minutes just after sunset and just before sunrise. For example, if the sun sets at 5 p.m., the blue hour would last from approximately 5:10 p.m. to 5:30 p.m.. If the sun rises at 5 a.m., the blue hour lasts from about 4:30 a.m. to 4:50 a.m.
The exact timing of the blue hour will vary from location to location and change depending on time of year and air quality.
Bottom line: The blue hour – when the sun is below the horizon, when the sky is deep blue and the landscape is suffused with bluish light – is a good time to take photos. Blue hour photos from EarthSky friends on Facebook, and more information about the blue hour, in this post.