Photo tips on Saturday: aurora
I have just returned from a trip that included 5 nights photographing the Northern Lights. So in this post I would like to cover how to go about photographing aurora.
First of all you need to have solar activity and areas of the sky that do not have cloud. There needs to be a certain level of darkness so summer time will not work. In general, peak activity is said to occur around the equinox (March 21 and September 21). In Tromso, Norway where I based myself the tour operators stopped going out at the end of March because the nights were becoming too short.
The aurora look much more intense in photos than they do in real life. To the naked eye most aurora start out as looking quite innocuous and appear as an area of relative brightness in the sky. At times it can be necessary to take a photo to decide if an area actually is showing aurora activity or not.
The photo below shows an image I made when it wasn’t completely dark. This was a night when a lot of activity occurred so it was unusual to see the lights before it was completely dark. You will see the difference with later images that are more intense when it is darker.
Setting up the camera
A wide angle lens should be used. I used a 16mm-35mm zoom at the 16 mm end on my full frame camera and it should be used wide open (f2.8 in my case). The focus needs to be set at infinity. A convenient way to do this is to set it up before it’s dark. A good tripod is essential.
There are no specific settings that will work on every occasion since the intensity of aurora varies. In general I would start with an ISO of 800, f2.8 and shutter speed 20 seconds. In other words I used the manual mode on my camera. I always shot in RAW so tended to use the automatic white balance setting (for later adjustment in Lightroom). Don’t be fooled to rely on the LCD display to decide if those settings are adequate you have to look at the histogram. If you aim to have the histogram ‘towards the right’ you will end up with less noise after processing. There seems to be debate whether or not to have long exposure noise reduction on – personally I did keep it on for single shot captures but some do not bother with this step. Those photographers rely on software like Lightroom to deal with noise reduction. If I had been taking a time sequence I would have turned off my noise reduction. If I had required more exposure I would start by putting up the ISO. A longer shutter speed would not result in pinpoint stars when using a 16mm focal length.
When there is ‘dancing’ activity a shutter speed of 20 seconds is too long and something more like 4 seconds can be required. This may require the use of a higher ISO although the aurora are more intense at these times so it is possible to over expose.
Finding a location to shoot
In general it is useful to find a good foreground for shooting, ideally well away from city lights. The following photos illustrate the potential effects of light pollution (although sometimes you will have to choose between light pollution and no shots due to cloud cover). You will see from the first shot, the effects low cloud activity has on light pollution.