Ask Art – Photographing Stars
Dear Art Wolfe – I have long admired your images of stars and star trails and have tried in vane to take some images like this myself but just can’t seem to figure it out. Can you share some of your secrets?
Chris – I’d be happy to and it’s really not a big secret. When you are photographing stars and star trails at night, first figure out which type of composition you are looking to create – pin points of star light or the long streaks of star trails.
For pin points, set your shutter speed to 30 seconds, any longer and the points of light start to become ovals and the image takes on a blurry look-especially if you are including the Milky Way. Set your lens to it’s widest aperture, ISO 1600 or higher and expose. Noise in an image is most prevalent in the darkest areas, in photographing stars you will have a lot of deep dark areas between the stars so turn on your long exposure noise reduction to help minimize what gets transmitted to the image.
If you are shooting star trails, the elongated streaks of light that arc across the image, you will need much longer exposures than 30 seconds, namely 10 minutes on up to several hours, just exactly how long depends on the focal length of your lens and the effect you wish to create. Just as longer telephoto lenses will “magnify” movement, such as camera shake when you are trying to hand hold your camera, the longer the lens the less exposure time needed before you start to see effective star trails. Essentially the telephoto lens is zooming in making small things larger, so in as little as 5 minutes of exposure a 400 mm lens will yield short but definite star trails. With a wide angle lens, say 16 mm, you will need at least 30 minutes of exposure before you will begin to see decent star trails in your final image. For arcs of light that traverse the majority of the night sky you are generally looking at exposures of 2-5 hours.
In the days of slide film you would simply leave your shutter open for the entire exposure using the bulb setting to manually open and close the shutter and your wristwatch to time the event. However in the age of digital you can not leave the shutter open for that long without risk of damaging the sensor and an ever increasing build up of noise in the image. Rather than exposing for 2 hours straight, you shoot 240 thirty second exposures (to equal 2 hours) and then later “stack” them using any variety of software tools such as Adobe Photoshop or Imagestacker.
So how do you take 240 pictures over the course of a couple of hours? You could sit there with your cable release and click the button every 30 seconds, and if you only ever plan on trying this once perhaps that’s what you would do. However if this is something you would truly like to explore (and you won’t “get it” just trying it once) you should invest in a cable release called an Intervolemeter. This is essentially a computer that allows you to program the camera to shoot those 240, thirty-second exposures through the night while you get a little bit of sleep before setting up for the next shot.
The most important part of shooting stars is to pay just as much attention to what is on the ground as to what is in the sky. You will want to incorporate some interesting elements from the landscape around you, mountain peaks protruding into the sky, whole trees or tree branches, rock formations, saguaro cactus, etc… you need to tell the complete story so the viewer can appreciate not only the stars but where you were when you created such a striking image.
When including the foreground elements you have several choices as to how to handle them. First you can allow them to be silhouettes by simply photographing the scene after the sun has set using their forms as artistic elements in the image – this is perhaps the easiest and most common approach. The second approach is to begin creating your photograph prior to the setting of the sun, at dusk. Capture your lower foreground elements in an image at sunset and then leave the camera undisturbed on the tripod. Once the sun has completely gone and you are ready to shoot the star trails as before. Later in post processing when you are stacking your images together you will have the dimly lit view of the landscape to include in your overall composition. Now is this cheating? No. This is simply the same technique I have used for years with slide film when I would create a dual exposure on the same slide, one at sunset followed by a several hour exposure later in the night without moving the camera. Stacking is simply how you achieve the same result in the digital age due to the delicate sensor.
The last technique I have used involves artificially lighting the foreground elements in your landscape. Using a light source such as a flashlight, powerful search light or even a flash unit you can manually paint light over the foreground images during your 30 second exposures. It takes practice to go over the foreground elements just right, if you pass over an area too many times you will create a hot spot, miss an area and it will be dark, but when all you have is a flashlight to “paint with” there is nothing to tell you where you’ve been and where you have yet to go. So practice with this and over time you will be pleased with what you are able to paint in the dark. Here in the northwest snow camping is a popular winter time activity and lights inside of your tent or igloo make for wonderful glowing foreground elements in these compositions.
When shooting star trails you have two basic choices for where to point the camera. You can either create concentric circles of light around a single point in the sky by aiming at the the North Star (Polaris) for those photographing in the Northern Hemisphere, or arcs of light by pointing your camera in any other direction. Be aware of which you are choosing to compose and include your foreground elements for framing and balance accordingly. Unfortunately there is no convenient star in the southern hemisphere to point your camera directly towards so you’ll need to find that magic spot some other way.
Lastly there are some atmospheric conditions to be concerned with when photographing all night – namely condensation on the lens. I have shot start trails in many areas of the world such as the dry deserts of Utah and Namibia where condensation is not a concern but if you were to shoot them with say the sea stacks of the pacific coast you’ll be battling fogging on your lens throughout the night. One approach is to use a small battery operated fan to blow a steady wind across your lens to keep it dry. A second, perhaps easier approach, is to tape hand warmers around your lens, the kind hikers and skiers use. You’ll need several and they are only good for one night worth of shooting but they will help keep your lens warm and dry.
Lastly it goes without saying you need really dark skies. Pick a time when there is no moon or just barely a sliver and choose a location as far away and sheltered from the lights of near by cities as possible. For the pacific northwest where I live this means heading into the mountains, which make for great foreground subjects to include in the composition.
Enjoy your adventure – Art Wolfe
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