Photographing the aurora borealis
The aurora borealis, also known as 'northern lights' or 'merry dancers' in the northern isles, gave a superb show during the evening of Sunday 6th March with it being seen across Scotland. The last time I had seen them was whilst living in Orkney and I was pleased to have another opportunity.
The aurora borealis is an interesting natural phenomenon caused by solar wind (charged particles released from the surface of the sun) ionising the upper atmosphere of the Earth. The ionized elements of the atmosphere release photons of light at specific wavelengths. It is this light that is observed during the displays.
Issues associated with photographing the aurora borealis.
There are several issues that the photographer has to consider whilst photographing the aurora borealis:
As it is night time focussing will be manual. If your camera has live view it can be used to assist the focus. Otherwise setting the lens to infinity or hyperfocal distance will suffice. On digital cameras focus can be checked and adjusted as required.
- To ensure sufficient light is available the aperture will probably be fairly wide, for example f1.4. 2.8 etc, depending on your lens.
- If the shutter speed is too long, for example 30 secs, the visible columns of light sometimes associated with the aurora borealis and often called 'curtains' can merge and lose coherence and merge into an a less interesting amorphous glow. Visible stars will also begin to show more obvious star trails in the final image. A shutter speed of 10 secs or less ought to ensure the light ' curtains' are maintained and minimise star trails.
- The ISO setting on your camera will be based on the intensity of the aurora borealis, the aperture used on the lens and the shutter speed. Modern cameras have excellent ISO sensitivity before 'noise' becomes a significant issue. Older cameras are less efficient and typically 'noise' becomes an issue at lower ISO settings.
As the exposures will be lengthy the camera ought to be supported on a tripod or other support, for example gorilla pod, to minimise camera shake during the exposure.
The example below was taken at f2.8, 10 secs, ISO 1250. The curtains of light are visible.
The example below was taken at f2.8, 30 secs, ISO1250. Only a minute separates the two images yet there are less details in the aurora borealis in the image taken at 30 secs due to the longer shutter speed.
Finally during the exposure a secondary light source, for example a torch, may be used to light the foreground if required. Using a light source in this manner during long exposures is often described as 'light painting'. I used a small torch in the image below to add a little light to the trees in the foreground.