Why Create Blue Hour Photography

January 2, 2019

Blue hour refers to the darker stages of morning and evening twilight, when the Sun is quite far below the horizon, coloring the sky deep blue. On a clear day, the transition between day and night can be a colorful spectacle, with the indirect sunlight tinting the sky yellow, orange, red, and blue. 

What is Blue Hour Photography

The blue hour refers to the phase of twilight when the Sun is so far below the horizon that the light's blue wavelengths dominate.

Because the blue hour is a colloquial term, it doesn't have an official definition similar to dawn, dusk, and the 3 phases of twilight. Rather, it refers to a state of natural lighting that usually occurs at daybreak - the pre-peak moment prior to sunrise - in the morning, and during the last stages of twilight in the evening, during the final transition of the dark blue sky and total - black sky - darkness.

The blue color spectrum is most likely to emerge when the Sun is between 4 and 8 degrees below the horizon. By this definition, the blue hour encompasses parts of both nautical twilight and civil twilight.

Why Is the Light Blue?

The different colors of twilight are created by an atmospheric scattering effect. As the solar elevation angle—the angle of the Sun above or below the horizon—changes during the transition between day and night, different wavelengths are filtered out by the Earth's atmosphere, leaving the remaining rays of light to color the sky in ever-changing hues.

During the blue hour, the Sun is so far below the horizon that the atmosphere scatters only the short-wave blue light, sending it back to Earth. Meanwhile, the longer red wavelengths pass through it and into space.

How Long Does Blue Hour Last?

The duration of blue hour depends on both the latitude and the season. In locations where the Sun is directly overhead at noon—for example at the equator during the equinoxes—the Sun traverses the horizon at an angle of 90°, making for swift transitions between night and day and a relatively short blue hour. At higher latitudes, the same process takes longer. At around 40 degrees north and south, for example in New York, it takes around 20 minutes in March. In Atlanta, in March about 10 minutes, or less.  

Generally, the best blue hour photographs I have created are in a 3 to 12 minute window depending on location and time of year. However, I must be set up waiting for the actual moment well in advance.

How is a location selected for blue hour photography

The blue hour is awesome for commercial or industrial clients because it combines saturated colors from the sparkling lighting to the deep rich blue hues of the sky. Since the light is soft and has a very high color temperature during that time of the day, it is best suited to capture artificial light sources, such as commercial buildings, plants and mills, cityscapes, buildings, bridges, or monuments.

To capture the magic of the blue hour planning ahead is required. Simply, blue hour is short—too short to start when the light is just right. Mark must preplan long before arriving on site. and make calculations using a special blue hour calculator. The exact time changes each day so determining when the sun will be at just the right angle is best. The final determination of whether Mark arrives onsite in the morning or evening depends on many factors.

The end results of blue hour photography is well worth the effort. Blue hour photographs are commonly used in marketing for commercial buildings because it makes an otherwise plain photograph come to life that will set your images apart from daylight only images. 

Blue hour photography is not ideal for every location or building, but awesome for many locations. Contact Mark for more information.

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