Learn how to Shoot Long Exposure & Astrophotography
Once you have a grip on how the exposure triangle works, then it’s time to take a shot at long exposure and astrophotography. In a nutshell, long exposure is a technique that requires you to control the camera shutter manually. You also have to have the image sensor exposed for a much longer time. It takes advantage of slow shutter speeds to produce unique looking photographs. Long exposure works best in scenarios where you want to indicate movement.
An example could be a waterfall or movement from a car driving by. They are also the ideal solution for shooting in dark conditions like the night sky. When applied to astrophotography, long exposure allows you to capture some of the most stunning images of the Milky Way and the Galactic Core.
What is Long Exposure?
As the name suggests, long exposure requires the camera shutter to be open for greater periods. In most daylight settings, you would set your shutter speed to around 1/250 to freeze any scene. Set it higher if you have moving subjects. But with a long exposure, you need to lower the shutter speed for durations as long as seconds and even minutes.
For example, when shooting a flowing waterfall cascading down a rock wall, a standard shutter speed will freeze the action. The individual streams of water will appear sharp and static.
To bring out the magic from the landscape scene, slowing the shutter speed will transform the falling water. With a shutter speed of 2-3 seconds, the scene will be frozen; however, the falling water will appear as opaque ribbons of movement.
What is Astrophotography?
Astrophotography involves capturing images of the night sky or an object in space whether it be stars, the moon or the milky way. In astrophotography, long exposure is necessary to capture the detail in the sky. While the human eye can spot hundreds of stars at night, a long exposure can pull out the detail by capturing thousands of them. With the shutter open for several minutes, there is sufficient time for the light radiating from those stars to reach the camera’s sensor. This will produce an extraordinary image like the one below.
The Best Gear For Long Exposures and Astrophotography
What Camera To Use
Shooting long exposures, especially in astrophotography, require the ability to control the camera’s shutter speed. In some instances, you will need to use Bulb mode. This is where you open the shutter with one press of the trigger and close it minutes or hours later with a second click. During that time, your camera sensor is likely to heat up, so having a camera that manages heat dissipation is a must. We recommend a medium-range mirrorless camera such as the Fujifilm X-T4, Sony a7R IIIa or Panasonic S5.
Firstly the Sony a7R IIIa is capable of capturing an impressive 42.2 megapixels which results in ultra-high-resolution photographs. Pair that with the CMOS sensor and efficient image processor, the camera is primed for taking images of planets and stars. It also has a 5 axis image stabilisation system which proves to be useful for long exposure shots.
Secondly, the Fujifilm X-T4 is a brilliant all-rounder option for astrophotographers. This is because the 26.1MP APS-C sensor performs very well and is capable of capturing high-resolution images.
Lastly, the Panasonic S5 has a live view composite mode which is a long exposure shooting mode, allowing for easier recording of night-time scenes. It is also a more sophisticated Bulb mode where the camera will continue to record new light as it hits the sensor. The great thing is it won’t simply gather and record light across the frame continuously. This means it won’t result in an overexposed image.
Use a Wide Angle Lens
As for a suitable lens for long exposures, it all depends on what you want to achieve. A lot of long exposure work involves landscape, and the best lens for landscape is a wide-angle. With long exposure and astrophotography, a wide-angle lens with a fast aperture of at least f/2.8 is also going to make a huge difference. The wider the aperture (such as f/1.4), the more light will pass through the lens to the image sensor.
Select a Sturdy Tripod
The trick with long exposure work of any kind is to keep your camera perfectly still. Any hint of camera shake, even just pressing the shutter button will be detected by the camera sensor. This will impact the quality of your image. The best way to manage camera shakes or bumps for long exposure work, especially in astrophotography is with a sturdy tripod.
We recommend using a Manfrotto Befree Advanced Travel Tripod as it is a robust support option, made of aluminium alloy with a sturdy centre ball head. This makes it easy to compose your Astro shots in the dark. Each leg is composed of four sections, which can be easily adjusted and securely locked into place. A side-pull selector also allows you to set up the tripod at three different angle configurations, enabling low angle shooting with the simple push of a button. If you’re wanting something a bit light and more compact for travelling purposes, we would recommend the Peak Design Aluminium Travel Tripod.
Reduce Blur with a Remote Shutter
Finally, to prevent any hint of camera shake (even with your camera on a tripod), we recommend using a remote shutter release. Depending on your camera, a remote shutter can be wired or wireless and, it acts as your remote shutter button. Modern DSLRs and mirrorless cameras can often be controlled with a smartphone app. It acts as a shutter button and even controls key camera settings for you.
However, if you find there isn’t one available for your specific camera, you can set the self-timer on your camera for 3 seconds. After which it will take a photo without causing disturbance to your camera.
Best Camera Settings For Long Exposure and Astrophotography
As mentioned, the camera settings for long exposure and astrophotography is different from what you would use during daylight hours. The exposure triangle is just as important and will require manual control to get it right.
Setting Your Camera’s Shutter Speed
Long exposures are all about keeping the shutter open for longer. This is so the sensor has more time to capture the image. Long exposure work generally requires shutter speeds of 1 second or more. If shooting daylight landscapes with a 3-second shutter speed, the photo will be over-exposed and unworkable.
That’s why ND (Neutral Density) filters are necessary for this kind of work. They cut out light from the scene you are capturing and in very well lit situations, you can easily reach limitations on settings and this is especially true if you are capturing long exposures. Of course, things are different when shooting at night. The same 3-second shutter speed may not be long enough to make out the landscape scene’s horizon line. With astrophotography, 10-seconds is a good starting point. The trick is to experiment with varying shutter speeds. This is to ensure that you get the best exposure and the stars appearing as sharp points in the sky. Due to the rotation of the earth, the stars will start to blur if you have too long of an exposure.
You can also use the ‘500 rule’ which calculates the longest exposure time possible for Milky Way photography before the movement of the stars starts to show. You want to divide 500 by the focal length of your lens. For example, 500 divided by 14mm would be 35.7. This means 35.7 seconds is your maximum advised exposure length. The reason for this is because when your perspective is tighter, the movement of stars is relatively faster. So the wider your lens is, the more time you have to expose it to the stars.
Which F Stop You Should Use
You should know the quality of your lens, so when setting the aperture, you can set it to its widest but sharpest point. A lens with an f/1.4 aperture may not be at its sharpest until it is stepped to f/2, where the whole frame is sure to be sharper. A wide aperture’s benefit is that more light is passed through the lens and internal elements to hit the image sensor.
Setting The Camera’s ISO
In some low-light settings, the rule is to dial up ISO values to 3200 and 6400. This will depend on the camera’s scenario and quality. There is the temptation in astrophotography to dial up higher to account for the lack of light but this will ruin your image. One of the traps of long exposure work is image degradation and noise appearing on your photos due to high ISO. Astrophotography starts with an ISO of between 800 and 1600 and works with shutter speed to control the light.
Take a couple of test shots and see how it looks and boost the ISO to a point you’re happy with. Just be careful of the fact that the higher you push the ISO the more noise you will introduce. It may look good on your small screen, but when you take it back to your computer, you’ll see that it’s not quite as bright and pretty as you thought.