Wednesday, August 27, 2014

South Pole Aurora Photography

With twilight rapidly erasing away the night sky, soon the stars will be completed washed out by the approaching sunlight. The aurora shot below is one of my last. The purple is most visible in the aurora seen near sunrise/sunset, because it requires sunlight reaching high in the atmosphere to induce the purple emission in nitrogen that is pre-excited by solar particles.

Although I was able to get some good aurora shots over the winter, I came to the pole woefully unprepared, so this week I'll be discussing the best cameras to bring to the South Pole to photograph aurora as a guide for future South Pole winterovers and aurora photographers. 

Although I believe that a lot of travel photography is more about framing and few people can really make use of or need a $1500 dollar camera, aurora photography is one of the instances where having an expensive camera is actually necessary. Aurora phenomenon occur on 2 to 10 second timescales in very low light conditions, so to capture a good aurora shot you have to have a very fast lens (F stop 2.8 or less), and a sensor capable of reaching a high ISO rating (3200 or higher) with low noise. Combine a low F-stop with a high ISO and a reasonable exposure length (4 to 25 seconds depending on the brightness of the aurora) and you have your shot. One also has to note that you will begin to notice startrails during exposure of 30 seconds or more, which sets an upper limit on the exposure timing.

To obtain a low-noise image at high ISO settings, you simply have to have a high quality sensor, which means purchasing an expensive camera. It can be useful to check out very detailed explanations of sensor noise on a site like this one or this one. Aurora photography is also one of the instances where having a full-frame camera can really pay off -- even if the number of pixels is the same in a full frame versus cropped sensor camera, the pixels in the full frame will be physically bigger which results in less noise because larger pixels collect more photons per image, reducing photon noise.

Despite the advantage of a full frame camera, they might be too expensive for some budgets because even if a full frame body is only a few hundred dollars more than a cropped sensor body, the lenses will be much more expensive. Fortunately, high-end cropped sensor cameras are still sufficient for aurora photography.

Here are some recommended kits:
Budget < $1000 - 1500
 - Canon Rebel Series with Kit or Zoom Lens (~$500)
 - Tokina 11-16 mm Lens (~$500)

Budget $2000 - $2500
 - Canon 60D or 70D with Kit or Zoom Lens (~$1200)
 - Tokina 11-16 mm Lens (~$500)

Budget > $4000
 - Canon 6D with Kit or Zoom Lens (~$1800)
 - 16 - 35 mm Lens (F 2.8) (~ $2000)

For a low end camera body, a rebel intro DSLR can still take good aurora shots. The Canon 550D that I used for many of my photographs had a surprisingly high ISO performance as a result of it having the same sensor as the Canon 7D. A lot of the additional features that are upgraded for high end cameras like the 7D, or the 5D over the 6D are additional focus points and ultra fast shutter speeds, which are not necessary for aurora photography. Indeed, you will be using manual focus for all aurora / night sky shots.

The Canon 60D and 70D are good high-mid range cameras. They take excellent shots at high ISO. Although I used to not like cameras with a movable screen, they are useful for previewing shots taken when your camera is in a box without having to remove the camera from the box (this is more annoying than it sounds due to the cold temperatures).

The best aurora camera on the market is probably the Canon 6D. This camera has about the same low-light performance as the twice as expensive 5D. It also has a special low-light sensor in the center pixel. It really produces amazing shots and I was fortunate to be able to borrow one often from another winter-over.

In addition to a body, you need an "aurora lens", basically the fastest (lowest F-stop) wide angle lens you can afford.  For cropped sensor cameras, the Tokina 11-16 mm Lens is amazingly sharp and fast for its price. Although I listed wide angle zoom lenses, a prime lens is also fine. Even with a wide angle zoom, you will probably keep it on its widest setting most of the time. A good focal length is 16mm for a full frame and 10 or 11mm for a cropped sensor camera. Metal primes are preferred as they have a bit less change in focal length due to temperature contractions in the cold. Another advantage of canon cameras is that they can use prime lenses from almost any brand with only a cheap physical adapter. So if you can find a good and fast prime lens off of KEH then go for it.

Once you have your wide angle lens, when you get to the pole you should focus it on stars and then use electrical tape to make sure the focus doesn't shift. You can also tape it down to the widest focal length and leave it that way for an entire winter of aurora photography.

The kit and accessories you buy will also depend on if you wish to take timelapse photography or just take stills. For example, the Canon 60D has a battery that lasts 30 minutes in the cold without a camera box, while the Canon 550D only lasted 15minutes (a large difference if you are taking an aurora timelapse).

Accessories:
  • In addition to your wide angle lens, make sure you have a zoom lens (up to 200mm) for taking pictures of sunrise/sunset, and if you are lucky a lunar eclipse. 
  • Other lenses: A fisheye lens is good for some all sky shots, particularly of corona aurora, and also if you want to install an aurora camera
  • Extra batteries: 3-4 should do it.
  • Memory cards: Get a few of these, with one really large one (128GB) if you plan to do long timelapses
  • Remote shutter: Bringing down a couple of these is a good idea, but you need to modify them with teflon so that the rubber doesn't break in the cold
  • Tripod: it seems the carbon tripods to better down here because they are easier to handle in the cold due to their lower heat conduction. The carbon fiber also doesn't contract as much as mental in the cold. A ball mount seems best for getting the best range of motion and is easy to adjust outdoors in the cold. So something like this should work (Dolica also has some good cheap ones), just keep in mind that when you get to pole you will have to take the tripod apart and regrease it with special cold-weather grease that you can find on station.
  • External Hard Drive: It's essential to bring one or two external hard drives down for storing backups of your images and backups of your backups (hard drives tend to fail easily in the environment down here)
  • Adapters: If you bring a canon camera, consider a Nikon lens adapter for borrowing lenses or to use on old primes you bring down
  • Extra camera: Yes! After all that investment in a kit for one camera, you should bring an extra camera body down (a $250 Canon 550D body should be fine). This will serve as a backup in case your primary camera breaks (this winter a Canon 5D MkIII broke a couple months after station closed) and can also be used as a camera for the aurora cam setup. I'd actually bring two extra bodies down, one for the aurora cam and one for putting in outdoor camera boxes. 


Camera boxes like the two shown above can be constructed to allow for long timelapses. The one on the top is electrically heated so can last indefinitely, but must be plugged into a power outlet. The box on the bottom uses two Nalgene bottles filled with hot water from the tea spigot in the galley to keep the camera warm for up to two hours. It is easier to frame shots in the boxes if your camera has a flip-out screen. 

You can check out some examples of south pole aurora photography at these links:
  • The iceman's blog follows the king of south pole photography's 10th winter and counting. He uses many different canon cameras. He even constructs camera boxes that mount on co-moving platforms to capture timelapses that follow the milky way
  • Icecube winterover Ian's blog Ian's blog has some good photos taken with a Canon 6D
  • Fellow SPT winterover Nick's blog has good still shots captured with a Nikon D7000
  • NOAA Corps winterover Joe's flickr page has good shots captured with a Canon 60D
  • And of course my shots are posted on this blog or on my flickr page


Other shots:

  • Although I list mostly Canon and they seem preferred down here, you can find an equivalent Nikon for any Canon model. Canon can fit used old primes from other cameras with only a physical adapter, which is nice, but Nikon has a bit better in camera options (to make full use of a Canon camera's options you can always get magiclantern)
  • Remember that once station closes you can't get anything new if a component breaks, so better just to bring two of every piece of essential camera equipment. It's probably too expensive to do this with lenses, but there are a couple lenses for the station camera that you can borrow
  • I didn't mention software, but there are good programs already down here on common drives, including Lightroom, starstax, hugin, timelapseassembler, etc...
  • What not to buy: People were unhappy with low end introductory SLRs such as the Pentax K-x and the Nikon D3200. 
  • Finally, our entry into the Antarctic International Film Festival tied for Best Screenplay and was runner up for Best Acting!

Next Week in Pole: NASA blows up the TDRS-5 internet satellite



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