It’s time for #TravelTuesday with Dave (I know it’s Monday; deal with it), and today, I want to touch on a landscape photography term that’s used throughout photography: blue hour. Let’s not waste any time, here goes.
Blue hour and golden hour go hand in hand. They aren’t accurately measured as being an hour, but we know them as the hour before and after the sun sets and rises when we have the best light for photography. The reason golden hour is so beautiful is because the light from the sun diffracts through the atmosphere as its beams travel through so much more of our atmosphere laterally than if the sun were overhead. When it comes to blue hour, there’s a whole other science at play.
Blue hour, in photography, is a fairly broad term when compared to the scientific community’s version of what blue hour actually is. First of all, the different colours of blue hour are caused by the scattering of the shortest wavelength of light—blue—based on something caller solar elevation. This, in real terms, is dependent on the season and latitude and is the angle of the sun below the horizon.
Blue hour is further broken down into different degrees of twilight, and the term “degrees” really helps us to understand why. When the sun is at different levels below the horizon, as measured by angle, results in different levels of light and different visibility of stars.
The first type of twilight, where the sun is highest in relation to the horizon at between 0 and 6 degrees below the horizon line, is civil twilight. The sky during this time can still be yellow or orange in the direction of the setting sun.
The next type of twilight, where the sun is between 6 and 12 degrees below the horizon, is nautical twilight. During this period, with clear weather conditions, the horizon is faintly visible. Many bright stars can be seen, making it possible to use the position of the stars to navigate when at sea, hence the name “nautical twilight.”
The next type of twilight, where the sun is between 12 and 18 degrees below the horizon, is astronomical twilight. Astronomical twilight is almost indistinguishable from nighttime to the naked eye. During this time, most of the stars and other celestial bodies can be seen. To be able to see fainter stars and galaxies, you’d still need to wait for the sun to pass lower relative to the horizon.
At anything lower than 18 degrees below the horizon, it’s simply dark!
It’s important to bear this little nugget of information in mind when planning photos. Different situations require different circumstances, and the circumstances won’t always exist. For example, at polar latitudes, we notice midnight sun during the summer where it doesn’t get dark at all for months according to the definition of night. We can find the timings for these twilight times by using PhotoPills or timeanddate.com
I hope that was useful. Have a great day!