Blue Hour is the time frame that precedes sunrise and follows sunset.
It is so named for the blue tones that occur in the sky as it transitions from full darkness through sunrise and sunset to full darkness.
Officially, blue hour is part of the time frame called “civil twilight” and occurs when the sun is between -6 and -4 degrees below the horizon
It typically lasts about 30-40 minutes but that can vary depending on conditions and geographic location.
So how do we shoot during Blue Hour?
As always, it's about finding a balance between ISO, aperture and shutter speed that is appropriate to the conditions.
The light changes pretty rapidly during blue hour, so your settings will likely change significantly in just a matter of minutes.
Ideally, you always use the lowest ISO possible to preserve image quality.
But this will be a trade-off with how long or short a shutter speed you are happy to use.
You can also balance your exposure in favour of your ISO by selecting a wide aperture of f/2.8 to f/3.5.
But by doing so you will be sacrificing image sharpness and depth-of-field.
An aperture of around f/8 to f/11 would deliver sharper results but would require a higher ISO setting and/or a longer shutter speed to balance the exposure.
This in turn would mean a decrease in image quality and/or a potentially 30-second plus shutter speed.
With a shutter speed of over 30-seconds, you'll need to hold the shutter open using either the bulb setting or time setting, depending on what brand a model of camera and/or shutter release you're using.
You will manually time the exposure. (Most smartphones have a stopwatch function if your shutter release or intervalometer does not).
Although not a deal-breaker, this technique takes practice and more than a little trial and error.
Since blue hour almost always results in a long exposure, it’s a great opportunity to capture movement or some sort of artificial light!
Ocean waves, waterfalls, a lighthouse, building or street lights….
In some cases, you’ll even be able to catch some of the brighter stars in the sky before it becomes too bright.
Basically, blue hour is a great opportunity to practice both long exposure settings and motion capture.
Think about what sort of creative movement you’ll want to capture, and scout your location for a strong composition.
You will likely need a flashlight or headlamp to both safely explore, set your focus and see the settings on your camera.
You’ll need to think about and try to anticipate the way the movement will lead you through your frame.
Once you have your camera set on a sturdy tripod, you’ll need to set your focus. If it is still bright enough (pre-sunset blue hour), you can use auto-focus.
Once the focus is set, however, you’ll need to switch your focus to manual, so it doesn’t search in the low light.
If you’re focusing in the dark, you can use your flashlight and live view to help you focus the camera. This is the same way you might focus for a night shot.
Once your focus is set, you can either switch to aperture priority or manual.
In either case, a decision about your aperture needs to be made – are you concerned about gathering light (and having fairly reasonable time values) or concerned about sharpness (which would result in much longer exposures and, potentially, hot pixels)?
If you’re using a wide-open aperture (f/3.5 or wider), then you can probably get away with aperture priority for the brighter portions of blue hour, as your time values will likely be under 30 seconds.
If you’re using an aperture around f/8, or you’re shooting the darker half of blue hour then you will need to shoot in Manual, so you have full control over your time value, including going beyond the standard 30-second cap.
To accomplish the extreme long exposures, you’ll need to set your camera to bulb and either carefully hold the shutter down (with a timer in the other hand) or use your remote.
These sort of long exposures are sort of a guessing game since the light is rapidly changing.
You’ll likely take a long exposure, then need to adjust ISO or use a longer/shorter shutter speed to get a proper exposure.
The good news is these sorts of challenging shooting conditions force you to think about how your ISO, aperture and shutter speed work together.
With some practice, you’ll find it becomes a bit easier to predict the changes you need to make as blue hour progresses.
If you have any questions, please don’t hesitate to ask in the Discord group! We want to help you guys grow your skills, and that happens best when we hear from you.