One of the big issues with Northern lights photos is noise.

What settings can help us control noise in our images?

 

If you are reading this, it is unlikely that you have a Canon EOS 5D Mark III, or Nikon D800.  These cameras can be pushed so far that noise is not really an issue, if it is, then read on (this might be for you after all).  That is one solution to noise in your Aurora images, upgrade to the new generation DSLRs, it is possible to push the iso to 3200 and still get usable results, this is very useful when you are shooting very low light subjects, such as Milky way, Auroras, Night landscapes etc.  If you are still getting noise with these cameras, then you need help!!


Aperture

The high iso noise control on the Canon EOS 5D Mark III DSLR Camera Kit with Canon EF 24-70mm f/4L IS USM Lens is very impressive.

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This was extreme low light!  There was no moon and despite the results, the Auroras were difficult to see with the Human eye.  This is my favourite shooting conditions because the result is a surprise.  This shot was at f/2.8, this is a compromise because my lens is f/1.4.  F/2.8 allows a lot of light and I knew the DOF would render the Ice in the middle ground to have acceptable focus.   If I focus just before infinity, I know that a 24mm lens will have a DOF extending into the middle ground.   Without any middle ground, I might have chosen f/2.2 to give my sky a little more exposure.    If that piece of ice was closer, I would have considered f/4 (with focus just short of infinity).

Just short of infinity: find your infinity focus and then just nudge it back – practice it – check your results – feel it!!

Magic Cloth

I took some test shots to establish a 2o second exposure, but this shot was 68 seconds, after 20 seconds, I covered the sky and continued to expose the foreground. More info about magic cloth: LINK

 

Noise

So why is this a noisy shot?

It is mostly because of the processing.  When I got home I found that the exposure wasn’t as good as I hoped, to achieve the look I wanted, I have had to really push some contrast, this naturally increases the noise signal.  If I could go back and do it again, the only difference I would make is to try exactly the same, but with iso 3200.  In post-processing, I have controlled the noise as best as I can, but I wouldn’t print this.  But it is quite an achievement considering the very low light conditions.

 

High iso noise reduction?  
Yes

 

Long exposure noise reduction?
I don’t use it in cold conditions.  What it does is takes the same exposure with no light hitting the sensor, it then subtracts the difference from your photo.  The difference is heat spots on your sensor from the extended use.  In cold conditions, I find this a wast of time because the sensor is not allowed to heat.  I have told everyone on my Winter workshops to turn it off and I never have complaints.  If you are concerned, you could take a similar exposure with a lens cap (and cover the eye piece).  There is a photoshop technique which can then apply the noise reduction to any noisy shots, but I tell you, you are wasting your time in cold conditions.

Exposure

Thanks for reading this so far!

This is the single most important consideration when you are shooting auroras.  The biggest mistake I see is that photographers check their images in the camera preview, their eyes have adjusted to the darkness and their images look stunning – they look exactly like you wanted – like a dream.  But when you get home, they have all come out too dark.  This is simply because your eyes are so sensitive when you check your image, that the preview screen appears to be several time brighter than it actually is.  What you need to be seeing on the back of your camera in the dark, is an image that looks almost over exposed.  Keep checking the Histogram to make sure they are not actually over-exposed.

 


 
This shot has a lovely, noise free foreground.  This is entirely due to being exposed well.  The sky has a short exposure less than 30 seconds to avoid star trails.  The rest of the scene had up to 3 times as much exposure again.  The good exposure level means that there is detail in shadow areas and in post-processing I can easily bring out colours with contrast curves without introducing uncontrollable noise.

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