Babak Tafreshi is an award-winning photographer who in 2007 founded The World at Night: a group of about 40 photographers across the world who seek to help people reconnect with the night sky above us.
The following extract is from Tafreshi’s new book The World at Night; a collection of nightscape imagery and astrophotography tips.
Thanks to the rapidly developing technology of digital SLR cameras, starting nightscape photography is now far easier than it was in the days of analog photography, when most The World at Night photographers began their careers.
Still, it is essential to have some knowledge of the night sky and practical astronomy in order to be ‘in the right place, at the right time’.
Planning is based on ideal weather and moonlight conditions, but factors such as geographic location, altitude and temperature, local topography and light pollution should be considered, too.
Compared to telescopic astrophotography, nightscape imaging is a low-gear endeavour; you don’t need a vast array of high-tech equipment.
A single camera with a fast, wide-angle lens, a tripod and a shutter-release cable are enough to get you started.
Keeping your equipment as compact as possible will also help you tackle the real challenge, which is getting to the right location.
However it is very important that your tripod is sturdy and reliable enough for long exposures and windy nights.
A proper ball head that can handle the camera load is far easier to use at night than a classic tripod head.
A popular option for the frequent traveller is a carbon-fibre tripod, versions of which can be just as steady in wind as heavier aluminium models.
An easy solution for making the system even more steady is to fill a bag with rocks or sand and hang it from the centre of the tripod.
The camera settings for many of the images in this article fall within the range of the ‘golden numbers’ of nightscape photography:
- exposures of 10 to 20 seconds
- ISO of 1600–6400
- lens aperture of f2–2.8.
We are bound to these due to the Earth’s rotation (sky motion) as well as the physical limits of lens design and digital sensor technology.
This type of photography requires cameras suitable for lowlight imaging with low noise performance in high ISOs – the highest practical ISO (6400 for many cameras) is necessary for when the night environment is very dark.
In moonlight or near cities you can create higher-quality images by reducing the ISO to 1600 or less.
High ISO imaging, although sometimes essential at night, results in more noise, fewer colours and less dynamic range.
It is very important to capture all images in ‘raw’ format (plus an optional JPEG for quicker preview).
Saving original files in a compressed-JPEG format alone will eliminate post-processing capabilities to enhance the image, to reduce the noise, to easily correct the white balance and to recover shadows and highlights.
Image processing is an important part of nightscape photography, since these images are technically challenging.
When photographing the night sky, you need to take the movement of the stars and planets into consideration.
The apparent speed of a star’s motion depends on how much your camera lens magnifies the view – the longer the focal length the faster the speed of the star, and the less time available to capture a pinpoint image.
For an average-resolution digital camera a simple equation known as the ‘300 rule’ will give you the maximum exposure to use in order to avoid star trails: you simply divide 300 by the focal length of your lens (300/F). The result will give you the length of exposure you need, in seconds.
For example, with a super-wide-angle 14 mm lens, ideal for wide views of the Milky Way, the maximum exposure is 300/14 – around 20 seconds before you will capture notable motion in the stars.
If the camera is not a full frame, with a smaller crop sensor, the F should be multiplied by the crop factor of the sensor.
On many models the crop factor is about 1.5x, but it is best to identify this on the camera sensor specification.
If your field of view is far from the celestial equator (either to the north or south) you can further increase the exposure.
For instance, midway between the equator and Polaris, you can exceed the exposure to 40 per cent and up to 70 per cent for the Big Dipper near the pole (or for the Crux and the Magellanic Clouds in the southern sky).
Using this simple ‘300 rule’ equation it’s evident that, when using telephoto lenses, only a very short exposure is possible before you start to see star trails.
That’s why more nightscape photographs are taken using wide-angle lenses between 14 mm and 35 mm (10 and 24 mm for crop sensor cameras).
The exposure limit for an 85 mm lens is only four seconds, for example, unless a portable star tracker device is used on top of the tripod.
This cancels Earth’s rotation by following the stars during the exposure, although the foreground will become blurry if the exposure is too long.
Since your goal is to collect as much light as possible during a short exposure, you should aim for fast optics.
A lens with a larger maximum aperture (smaller minimum F-number) delivers more light intensity and reduces the needed exposure.
The fastest lenses are usually prime, with fixed focal lengths. Most long-range zoom lenses are not desirable for low-light photography.
For instance 18–200 mm or 24–105 mm f4 are very handy in daytime but too slow at night.
The fast f1.4 prime lenses are some of the most popular among nightscape photographers, as well as short-range f2.8 zooms such as 14–24 mm or 16–35 mm.
After an imaging session, the main challenge is how to create a natural-looking image.
While the natural daytime colours are evident, most photographers are not familiar with the natural colours of the night sky.
They often shift the white balance or apply saturation in extreme ways as a result.
The natural colours of the Milky Way and the night sky are best preserved in a white balance range of 4000–5000 Kelvin.
Much lower (colder) white balance results in a blue Milky Way, whereas it should be pale yellow (especially towards the galactic bulge).
You should also try to avoid the habit of ‘over-cooked’ processing, in which the colours can become saturated, for example. In nightscape imaging, it is essential to preserve the originality of the scene.
Composite images, made using different lenses and a montage of daytime and night-time frames have their own value in art, but are not usually recognized as nature documentary photographs.
- It’s important to reduce the risks involved with night- time photography.
- Always inform others about your intended location and avoid shooting alone in remote locations.
- Being in a small team of two or three is the most pleasant way to experience night-time photography.
- If in larger groups, plan around such potential issues as having too many tripods, similar image results and moving flashlights in your photos.
- Always arrive at a location before sunset. This will allow you to become familiar with the environment and to identify potential obstacles around you.
- Always consider unpredictable issues regarding accessibility, wildlife, access restrictions and reactions from locals to your after-dark presence in their neighbourhood. Such risks are reduced when a photographer arrives on site earlier in the day.
The world at night: a gallery
Take a look at selection of astrophotos captured by The World at Night astrophotographers