Time to be with your loved ones

Time to be with loved ones

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A friend has been kind enough to lend me a DSLR for a few months. It's my first foray into DSLR photography, or indeed any kind of photography beyond simply aiming my Canon IXUS at something and clicking the button.

Over the last few weeks, I've been busy studying, practising and trying to learn as much as possible ahead of a planned trip to Norway where I hope to see, and get some photos of, the Aurora Borealis.

I currently have:

  • Canon Rebel Xsi (450D)
  • Canon 50mm f/1.4 L
  • Canon 18-55m kit lens
  • Aluminium full height tripod with ball head
  • Cable release
  • Spare battery & memory cards

I'm prepared to spend the night wrapped up outdoors, in the hope that they will make an appearance. I'd like some advice on how to get the most out of this kit for the trip:

  • How should I go about setting up to get pics of the Aurora?

  • How might I achieve optimum focus?

  • From what I've read, I'll need to use the tripod and cable release, with IS turned off, on continuous shooting mode with long exposure times. But I'd like some more specific tips in terms of which aperture and ISO settings might work best?

  • Should I use one of the lenses above, or would it be worthwhile renting a better, wide angle lens; if so, which would you recommend?

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How did you do, Winston? –  Andrew Heath Jan 18 '12 at 9:24
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3 Answers

up vote 23 down vote accepted

I've never attempted to photograph the Aurora Borealis myself however the following advice applies to most celestial photography:

You will want the fastest (biggest aperture) lens you can get your hands on. The 50 f/1.4 is ideal, though the focal length is quite long for this sort of thing. It's good because it will let in about 5-6 times as much light as the kit lens! Fast wide lenses are a rarity for crop camera bodies such as the 450D. If you need to go wide you might get away with a Sigma 20 f/1.8, the other alternatives are not cheap: the Canon 16-35 f/2.8L would be better than your kit lens, but I'd personally go for the 24 f/1.4L even though it's not as wide.

  • In terms of focussing, for the lights themselves you'll probably want the lens set to infinity (i.e. as far as the focus ring will go) or occasionally just short of infinity. Given that the lights are very far away (i.e. the upper atmosphere) your depth of field at this focussing distance will be huge. If you want to get some foreground in for scale / composition, then obviously you need to set focus for that distance from what I can tell the Aurora are kind of fuzzy anyway to it wont matter too much if you have to focus closer. AF probably wont work in that sort of light so you focus by trial and error or maybe use live view to focus.

  • Shutter speed is a compromise between letting more light in to minimise noise, and avoiding motion in the images. I don't know how fast the Aurora move but this will probably limit your shutter speed. Noise can also increase with shutter time due to the sensor heating up however this might not be a problem where you're going! Multiple short exposures are generally better than one long one.

  • To reduce noise you need to get as much light down the lens as possible, and then set the ISO as high as possible (without overexposing). This sounds counter intuitive so I'll explain a bit more. High ISOs don't cause noise and actually exist to reduce noise. Noise comes from the sensor electronics, but also from the random nature of light itself. So it's not high ISOs that cause noise, it's low levels of light. The confusion originates from the fact that using a high ISO in auto mode will allow a faster shutter speed and result in more noise, however the noise is a result of a fast shutter letting in less light. If you're already letting in as much light as possible, then lowering the ISO will reduce the amplification on the sensor, and when the values are read out they will be lower and thus the readout noise will be higher in proportion. When you correct the exposure in post you amplify this readout noise. When you use a high ISO, the analogue signal is amplified before readout occurs so you don't end up amplifying the readout noise. If you still need convincing, check out this example of an underexposed ISO100 is far noisier than a correctly exposed ISO1600 shot. For the settings used, increasing the ISO, even to 1600, decreased the noise: http://www.mattgrum.com/ISOcomparison/ISO_100_vs_ISO_1600.jpg

Generally when working at night stacking is the way to go. This means shooting many shorter exposures and then combining them on your PC to produce a single image. There are many pieces of software that will do this for you, Deep Sky Stacker is one of the best. The software is designed to cope with the movement of the stars, it may be able to cope with the aurora moving as well, or you might get some ghosting.

Other things to bear in mind are that cold dramatically reduces battery life, so keep one battery in an inside pocket close to your body and swap them often. This probably wont affect you but if you're shooting exposures around 1/2s you should use the mirror lockup function to avoid the mirror slap causing vibrations which can show up in the image.

I would also recommend searching flickr for photos of the Aurora, most of the images will have the EXIF information still attached so you can see what camera settings / lenses other people are using.

Good luck!

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You can't directly compare them but the 24 would be better for you purposes as it has a much bigger max aperture which means it will let in 4 times as much light! Lack of light is going to be your biggest problem. –  Matt Grum Oct 21 '10 at 14:56
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@Matt Great coverage of a lot of issues. Your answers are always worth reading. –  whuber Oct 21 '10 at 15:00
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If you make the assumption that you need to brighten the resulting image during post-processing, then yes, ISO800 might end up looking noisier than ISO1600. But thats making the assumption that you need to increase the exposure of the image during post-processing. I'm able to get some great shots of the milky way with a 50mm f/1.8 at ISO 800 that don't require brightening, and given that the auroras are brighter than stars, I would imagine ISO 800 to be great at f/1.4. The auroras don't move fast enough to need a super fast shutter speed and a higher ISO (they change over a period of minutes.) –  jrista Oct 21 '10 at 18:12
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I'm not saying "use the highest ISO your camera can muster", I'm saying: "use the highest ISO you can for the exposure you've chosen". Otherwise, you will have to brighten in post, which will raise noise more than upping the ISO would have done. If you get the exposure you want at ISO800 or ISO400 then that's fine - you're minimising noise for that exposure. The idea that high ISO = more noise is so ingrained it's difficult for people to accept they can get less noise by rising the ISO! –  Matt Grum Oct 21 '10 at 18:52
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Good idea to browse Flickr and examine the EXIF data on others' shots! –  pkaeding Oct 21 '10 at 21:35
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enter image description here

Here is the exif info.

I think is quite light, but I'm working on it :). If the aurora is strong than is not quite so difficult, probably a 5-10 seconds exposure will do it. I do my photos with 25-30'.

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Turned out pretty good! I was surprised to see the aperture open to f10. I am about to go out tonight and try this (strong possibility of norhtern lights where i live tonight) and based on all the reading i've done people keep suggestig fast glass. Well the only one I have is 50mm over a cropped sensor which is not wide enough for what i want. In any case, based on your photo here I will also try my wide angle (f4 max) –  Jakub Jan 27 '12 at 20:00
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Beyond the technical aspects of setting up your camera(which has already been covered by Matt Grum quite well in another answer), the atmospheric conditions are an important component that you will want to understand.

The Kp Scale, Kp Index, or NOAA G Scale are reasonable ways to summarize the global level of geomagnetic activity. The Kp Index can range between 0 to 9, with 9 indicating the highest amount of geomagnetic activity. Typically to achieve a good aurora images, you would want a Kp Index of 4 or higher.

This is my favorite website to check the current Kp Index: Spaceweatherlive.com But also worth checking out are: Spaceweather.com and SolarHam.com

Your distance from light pollution is very important when capturing auroras. I would recommend using the Dark Sky Finder (USA only) and trying to be at a minimum darkness of the blue areas of the map. This means that almost the entire eastern United States is not a great place to photograph auroras! You could still do it, but it just won't be optimal with all of the light pollution. The lights only occur from about 50-400 miles above the earth's surface, so light pollution isn't quite as impactful as star photography, but it still plays a role.

Another option to assess light pollution is the Blue Marble Navigator, which works worldwide.

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Kjell Henriksen Observatory has an Auroras forecast map for the next hour. (Forecast link is on the sidebar) –  Esa Paulasto Oct 16 '13 at 19:45
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