by Roy Hooper

I recently had the opportunity to see Northern Lights for the first time, and at the same time, to photograph my first aurora borealis photos. I am thankful that I had a digital SLR, otherwise most of my images would have been marginal at best. The digital camera gave me the opportunity to learn as I was taking the photos what worked and what didn't. It also gave me the opportunity to correct the images afterwards for flaws such as underexposure or excessive noise due to high ISO.

I had no prior experience taking aurora photos the night I went out to take photos, and came back with several dozen great photos. If I can do it, you can too!

Finding Aurora Events

The first and most crucial step to taking photos of the northern lights is to find some to photograph! Fortunately, in this modern age of electronic information, there are many web resources to help you predict and locate active aurora. Some of these are:

• Spaceweather.com
• Geophysical Institute Aurora Forecast at the University of Alaska
• POES Auroral Activity Map
• Space Environment Center
• Solar Terrestrial Dispatch
• NRCan's Spaceweather and north america forecast map

If you keep a close watch on spaceweather.com, you should get advance warning of potential aurora activity. They announce geomagnetic storms that may cause aurora activity. Also, be sure to keep an eye on your local weather! There's not much point going out to photograph northern lights when the sky will be overcast.

Finding A Good Spot

The next step is to be at a good location. Ideally, a good location will have an interesting, but not overpowering foreground, minimal light pollution, and enough open space that you can get a great 360-degree view of the sky. If you can't get a 360-degree view, a northerly view is your best bet.

You should scout out some locations in advance, during the day. This is especially important in winter when the temperatures are cold. You don't want to get yourself in trouble wandering around at night in sub-zero temperatures. Also be sure to talk to other local aurora photographers. They will generally have an idea of places that offer a good variety of foreground elements. They will also tend to track aurora forecasts closely and actively plan which nights to go out on. The company of another photographer is also more fun and safer in extreme environments.

Get away from the city! City light pollution will decrease the intensity of the aurora you can capture on film. Get as far away from the city as you can.

On my first try, there was little notice before going out. There wasn't much chance to do advance planning to get interesting foreground for my photos. I was happy to settle for a location that was away from the bulk of the city's light pollution and in a nice open space with excellent sky coverage. Also, be certain that no cars will drive by and light up your foreground unevenly or flare your lens in the middle of a long exposure!

If you can't find an exciting foreground, a tree line or cabin will suffice in a pinch. A tent with a light inside is also not uncommon.

• My photos from November 7th, 2004
• Darrell Larose's Photos from the same place, same time

The Right Equipment

• A camera capable of long exposures (between 5 and 60 seconds)
• A camera with moderately low noise at ISO 400 (or good film)
• A wide angle lens and optionally a telephoto lens
• A good tripod with a ball head or pan-tilt head capable of pointing straight up.
  If you have a pan/tilt head that can't point straight up but can point straight down, put the camera on the tripod head backwards.
• Empty memory cards or unexposed film
• Fresh batteries
• A cable release or remote shutter release cord or remote control
• A small flashlight

Also, depending on where you live and the time of year, you may also need to dress warmly. If your camera has issues operating in the very cold weather, you may also need to find a way to keep the camera warm. Bringing a fold up chair is also an optional but valuable item if you're spending a lot of time waiting.

Choice of Camera

I have no experience taking aurora photos with anything other than my Canon 10D. I won't go into detail here on how to take good aurora photos with a film camera, as I haven't done so, but many others have!

Any good DSLR that is capable of relatively low noise long exposures will work well for the task. Many other digital cameras will work as well. If you're not sure if your camera will suffice, take it outside at night and take a few tests photos. Pretty much all DSLRs on the market except perhaps the Canon 1D are known to work well for long exposures. The Canon 20D is reported to be one of the best at high ISO on long exposures.

Here's some older information on how to photograph aurora with film at Dick Hutchinson's article.

Choice of Lens

Most DSLRs are not full frame sensors, so the choice of lens is a bit trickier than with a 35mm film camera. For example, on a Canon D30, D60, 10D, 20D, and Digital Rebel, the cropping factor is 1.6x. This means that an acceptably wide 28mm focal length only shows the equivalent of 44.8mm of sky – a "normal' view. While this will work, you'll find yourself rapidly frustrated that you can't get enough of the sky into the image when there's activity all over the sky. To get enough of the sky in, you're going to want a lens in the range of 12-18mm. This will show about the same amount of sky as 19.2-28.8mm on a 35mm camera. I found that my Canon 17-40/4.0L was a worthy lens for the purpose of photographing aurora. A lens slower than F/4.0 is going to be troublesome to work with, as exposure times and/or ISO will need to be bumped up to compensate.

There is also room for use of a longer telephoto lens to zoom in on distant displays or small parts of a larger display, so don't leave your longer lenses at home.

NOTE: Be sure to remove your UV filter and any other filters you may have on your lens. The filters will likely cause concentric rings. Have a look at Dick Hutchinson's article for more information.

Taking the Photograph

I am an avid proponent of using RAW mode. RAW mode provides lots of valuable features that let you recover from small errors as well as lets you perform enhancements later during "development". I recommend you use RAW mode if your camera supports it.

Suggested Camera Settings

• RAW mode
• Daylight White Balance
• ISO 400
• F/4.0, 30-40 seconds or F/2.8, 15-20 seconds
• Histogram enabled
• Low LCD brightness

Taking the exposure

You're going to need to focus your lens at this time. Auto-focus may not work, and your infinity mark may or may not be accurate. Manual focus is your friend, but is very difficult with a small viewfinder in dim lighting. I suggest setting your lens to the infinity focus mark and then fine-tune the focus using the viewfinder until you achieve infinity focus.

After establishing a good focus and setting the basic settings, it is time to check the exposure. I took my exposures in Manual mode, and set the aperture to F/4.0 (the widest my 17-40/4.0L would go), and set the shutter speed to 15 seconds. I took the photo, and had a look at the LCD and histogram. My image was there, but the exposure was too low and filled only the lower half of the histogram. Unfortunately, I only had another stop of exposure to add, when I really wanted to add 1½ to 2 stops, so I settled for ISO 400, F/4.0, 30 seconds. 40-60 seconds would have been better in many cases, although 60 seconds may have blown out. Keep an eye on the histogram as the conditions change and adjust your exposure to suit.

Recalling that the image was still being underexposed by at least a full stop, there were a few choices to deal with the situation. I could bump my ISO, use bulb mode and expose for 60 seconds, or compensate later in RAW conversion. I opted for the latter, to be able to take more exposures.

As time passed, the storm intensified, and the northern lights were everywhere and moving around quickly. I made a decision to jump to ISO 1600 and to take 8 to 10 second exposures rather than taking 30-second exposures. I knew that the noise would be objectionable, but I was hoping that I'd be able to at least learn what it makes a good aurora photo later. It turns out that despite the noise being objectionable at ISO 1600, tools exist to make these images useable.

The Composition

This is the one area where I know I could have improved my images dramatically. My images lack strong foreground elements such as a cabin, cityscape, reflection or waterline to give the compositions dynamism. I would have been better served to have some such element rather than the simple forest silhouette. A more interesting tree line may have been sufficient to strengthen many of the images. Additionally, you can take photos of northern lights without a foreground element to anchor the eye and give orientation. The latter is more difficult to work with, as the image becomes abstract. Fortunately, it removes the constraint of having the foreground straight and in the frame. You gain great freedom to tilt the camera any which way you like to capture the interesting patterns and shapes within the entire sky.

The foreground element isn't the only part to capturing good aurora photos. Look at the skyline for patterns and shapes with interesting compositional elements. Be on the lookout for curves, waves, s-curves, beams, and other interesting patterns. When your camera is busy taking an exposure, use the 30 seconds to look for the next exposure. Think ahead, and be don't be afraid to move the camera mid-photo if you've spotted something that excites you much more than your current exposure. There's a chance that the motion blur and possible double image could be interesting too!

Try to avoid exposing your eyes to bright lights. A dim flashlight is better for this than a bright one. Your eyes will see the aurora and the colours within them better as they become accustomed to the darkness. Turn your LCD down to a lower brightness setting to help with this. Look for faint red and other colours to give your photos some punch.

Here's a few galleries that contain compositional ideas for aurora photos:

• Adam McDiarmid's Aurora Gone Wild 2004
• Stan Richard's gallery
• Calvin Hall Photography's Northern Lights
• Ketil Monsen's Night Flame and Aurora borealis at Usefilm.com

First Looks

When you get home, you're going to _gone_wild_2004want to look over your images! I know that I couldn't wait to see what I had. At first, I was disappointed with my results, as many of the images were underexposed and thus unexciting. The aurora were dim in many exposures, lacking punch. There were a few that were overexposed, and a few that were blurry due to camera shake. After the initial shock of disappointment wore off, I recalled that I had purposely underexposed to keep the exposure times at 30 seconds or shorter. This is when I started to do the "post processing" on my photos.

Post Processing

Post processing isn't quite the right name for the first phase of post-exposure work. As I had used RAW mode, my first step was RAW conversion. During the conversion process it is possible to make adjustments to improve the image. These adjustments include exposure increases, contrast adjustments, white balance changes and fine-tuning, saturation, and sharpness (as well as other adjustments in some RAW conversion tools). After RAW conversion, however, I did perform some true post processing to remove ISO noise.

RAW Conversion

To do my RAW conversion, I used Adobe Photoshop's RAW plug-in. It provides extensive controls and is easy to use. For the underexposed images, I added the missing stop to stop and a quarter of exposure. The white balance was set to daylight where necessary, and 3% saturation was added. It would have been possible to add more, but overpowering saturation would detract from the overall results. In my experience, 3% more saturation gives a pleasing result to images shot on the 10D. Additionally, for each image, the black level and contrast were adjusted to suit. At this point, the images were saved to 16 bit TIFF format for later processing, such as conversion to sRGB JPEG files for posting to the web.

At first, I believed that there was no further need for adjustments to the images. I accepted the grain in the ISO 1600 images as an uncorrectable flaw in the images, and tried to live with it… That is, until I made an 10" wide print of one of the ISO 1600 images. All I can say is YUCK! The noise was horrible. I was shocked and dismayed but hadn't yet given up. I recalled that software and Photoshop macros existed to deal with noise reduction in images. Perhaps one of these could help my cause?

Thus began the second phase of the journey...

Noise Reduction

This is what I consider to be true post processing. This is something that isn't possible with film based photography without bringing the image into the digital realm. The noise reduction journey began with Google. It didn't take me long to stumble upon Neat Image and then Michael Almond's in-depth Noise Reduction tool comparison. I scanned through his review and jumped to the last page on which he mentions the best two tools are Neat Image and Noise Ninja. I downloaded the free evaluation versions of both programs and gave them both a try on my noisiest image. At first, Noise Ninja seemed to be the better tool for the job, but I soon discovered that Neat Image had an advanced mode where I could fine tune the noise reduction parameters, including turning on a "very low frequency" option. It didn't take long for me to get the image to look better in Neat Image than it did in Noise Ninja. The review pegged the two tools as pretty close rivals, and both programs have had new versions since the review. I prefer the UI in Neat Image. My personal vote goes to Neat Image.

Here's an example of how well Neat Image works on aurora photos:

Before Neat Image

After Neat Image

And here's a 1:1 crop from the middle of this image. Note how well Neat Image preserves most of the stars. With some further tweaking, it would be possible to restore some of the fainter stars at the expense of bringing back some of the noise. I purposely stopped from pushing Neat Image further as the very slight grain improves the overall appearance of this image when printing it.

Before Neat Image	After Neat Image

Conclusion

Taking aurora photos is lots of fun. Once you get past finding yourself some northern lights, the rest should be easy. Keep an eye on the space weather forecasts and be ready to go out to take photos at a moment's notice late at night. If you do a little bit of advanced planning, you should be able to come back with a couple dozen great images without much effort. Scoping out spots with good northerly views before the next batch of aurora come our way is perhaps the best bit of preparation you can do before the next time the sky lights up. If I can take a bunch of good aurora photos on my first attempt, so can you!