I'm really keen on taking photographs at night, usually trying to capture the milky way, constellations, planets and meteor showers set against interesting landscapes.
But I have a problem.
This photo was taken at Llanddulas on the North Wales coast, an area which is quite highly populated and is near the major urban areas of Chester, Liverpool and the well lit North Wales coastal strip, as you can see on the accompanying light pollution map.
This makes taking photos of the night sky tricky to say the least, as the stars are pretty much invisible against a background wash of orange haze from the streetlights, especially where the air is moisture laden at the coast.
So how to overcome this seemingly impossible problem?
Well, fortunately for me, help was at hand in the form of an internet tutorial from astrophotographer Ian Norman, of lonelyspeck.com.
How I applied the techniques I'd learnt from the tutorial to come up with this final image of the milky way over Colwyn Bay is the ongoing subject of this essay.
The fundamental principle behind this method is to capture as much light as you can when you take the photo, even if what appears on your camera's monitor looks completely useless (and it will do!)
With that in mind, I used the following list of equipment that I find gives me the best light gathering potential for my budget.
Camera - I used a Canon 6D. A modern DSLR camera with a full frame image sensor and a modest pixel count. This means that the individual photosites are relatively large which allows more light to be captured before highlights start to burn out.
Lens - I recently acquired a Samyang 14mm f2.8 lens. This is a modestly priced lens (compared with brand name versions) that works really well for photographing stars. I used it wide open at f2.8 to allow as much light through to the camera's sensor as possible.
Tripod - A sturdy tripod is a must for photographing at night, as the camera's shutter will be open for 15-30 seconds, and any camera movement will blur the stars. I used my trusty carbon fibre Manfrotto to hold the camera steady but I also used a remote cable release on the camera to avoid touching the set up at all when taking the photo.
And that's it. A very straightforward set up aimed at capturing as much light as possible.
All camera adjustments and options were controlled manually, with settings as described below.
File format - The image was shot in the RAW file format. This preserves all of the data captured by the camera's sensor, and I needed as much data as possible for subsequent post-processing. Shooting an in camrea JPEG would have reduced my 14 bits of raw data to 8 bits, and would have cramped my colour space down from what my camera was capable of to a much smaller sRGB colour space. These restrictions would have severely reduced what could be done with the image later on in post processing.
Focusing - The lens was focused manually on a bright star using the camera's magnified live view function.
Shutter speed - I set the shutter speed to 30 seconds, again, with the emphasis on capturing as much light as possible. 30 seconds is the maximum speed I could use with a 14mm focal length lens before the stars showed obvious streaking as the earth rotated during my exposure.
Aperture - I used my 14mm lens wide open at f2.8 to allow as much light as possible into the camera. This lens is great wide open, giving very good definition to the stars at this aperture.
ISO - Having set the shutter speed and aperture I then took a series of test shots at different ISO levels to see how high I could take the ISO before the important highlights in the image started to burn out. In the end I settled on an ISO of 6400, which pushed my exposure as far as it could go before blowing out details.
White balance - When shooting in the RAW format the white balance setting isn't that important, as it can (and will be) easily adjusted in post processing. I had the white balance set to 'Daylight' for this shot, which resulted in a very orange preview on my camera's monitor screen.
Added together, these camera setting resulted in an image file that looked horrible on my camera's monitor, but contained as much colour and luminosity data as it possibly could.
Satisfied that I'd done the best I could at the image taking stage of the process, I went home and started on the post-processing.
It's in post processing the image captured previously that a sow's ear gets turned into a silk purse.
Looking at the file straight out of the camera (screenshot#1) it looks a hopeless task to get anything worthwhile, but thanks to having captured as much light as possible (as evidenced by the circled histogram) when taking the photo there's a lot of leeway available for enhancing tone and contrast - so let's get to it!
All the post processing for this image was carried out in Adobe Lightroom CC, and if there's any software available that would be better for this task I'm not aware of it, but as always, your mileage may vary ;-)
Before getting stuck in I converted the native RAW file (.CR2) from the camera into Adobe's universal .DNG format. This isn't essential but it's my preference, as I keep all my RAW files in this format for archiving purposes.
The first real post processing task was to fix the errors induced into the image file when the photo was taken.
As I said previously, the Samyang 14mm f2.8 lens is great, but it does have its limitations, with noticable distortion and heavy vignetting at f2.8.
Some manual lens correction adjustments (see screenshot#2) soon got the horizon straight and fixed most of the vignetting.
Next up was fixing the white balance from that ghastly orange to something a bit more pleasant.
A good trick I learnt from Ian Norman's tutorial was to temporarily whack up the vibrance and saturation to the max and then adjust the white balance and tint to give a balance of colours in the image ranging from blue to orange (see screenshot#3).
The vibrance and saturation can then be returned to normal to give a reasonably neutral looking colour palette. (See screenshot#4).
Now comes the heavy lifting processing wise, where maximising the amount of light captured when taking the original photo comes in very handy.
All the adjustments I made were to do with the image contrast. I was quite happy with the colours of the final image once the contrast had been adjusted, so I made no further changes to hue or saturation although these options were available to me.
See screenshot#5 to see details of the adjustments I made.
Firstly I reduced the overall exposure of the image by 1.3 stops, which darkened the sky and foreground. The great thing about reducing the exposure is that annoying background noise is also reduced significantly. This is the main reason why the original exposure was set as high as possible, so that when the exposure was reduced in post processing to a more visually pleasing level the noise generated by the camera's sensor and electronics during the long exposure would be much less noticeable.
This reduction in background noise then allowed for serious tweaks to the image contrast, highlights, shadows, whites and blacks, allowing the bright stars of the milky way to be seen much more clearly against the night sky than was the case before, without banding in the sky or an unacceptable increase in noise that would have been the case if I was working on a file that had had less exposure at the time of capture.
You may have noticed from screenshot#5 that I left the clarity adjustment at zero. I initially tried increasing the clarity to further emphasise the milky way against the dark sky, but I found this to be rather crude, affecting other areas of the sky adversely.
So instead I tried out the new 'Dehaze' function that is available with the latest version of Lightroom (see screenshot#6), and found this to be a much more subtle way of further enhancing the appearance of the milky way without adversely affecting the fine detail in other parts of the image.
So there you have it.
What seemed an impossible task, photographing the milky way in a heavily light polluted sky, made possible using a techinque that, at first glance, resulted in a horrible, bright orange photo that I would have normally just deleted as a failure.
My thanks to Ian Norman at lonelyspeck.com for sharing his experise so freely.
Now I'm off to find some decent dark skies!
All content copyright © Howard Litherland 2009-2018 unless otherwise stated.