I’ve been planning an astrophotography trip to a salt lake like this for a long time. The last post – Salt Lake Hunting – was in immediate preparation for this visualisation. I’ve arguably been looking at doing this for a couple of years now. Last year (2014) I managed to do some limited scouting, however felt that it was too late for me to effectively use it. The lake that I found last year was heavily ruptured and the pressure ridges were no longer intact. The year before then, I had started to conceptualise it.
I’ve described them before, salt lakes in Australia are made from either natural erosion where minerals wash down into basins and then can’t move anywhere else and short term lakes that evaporate and create salt pans. Another way which is quite common here in Australia is where land clearing has caused the ground water to rise because deep root trees don’t draw the water anymore and bringing the minerals to the surface. A good information source is here – Salinity and Water quality.
The salt lakes change substantially throughout the year. At the moment in the trailing end of summer – the water has been dropping and the surface of some lakes has solidified and in the contracting process as it dries, pressure ridges form and create interesting geometric patterns on the surface. It was amazing how different the salt lake appeared to three weeks ago when I was last there. Closer to the edge of the lake where I’d scouted previously the surface had contracted a lot more and many of the clean ridges had cracked and looked messy. I had to travel further into the lake to find a satisfactory surface. I managed to find a location – but not far from there the pressure ridges ceased altogether and was a purely flat surface like sandpaper and rather flat.
I wandered around and setup for the first image composition – a vertical panorama star trail. Star trails are one of the rare times that I will stack images from different times. As per my previous post – star trails – the foreground shot will be captured at dusk and then keep shooting when it gets dark enough and blend the exposures together. I encountered a problem before with my “passage of time” star trail that the lens wasn’t wide enough by itself so didn’t manage to compose it quite the way I wanted to. Setting off the camera I returned to the car and ate dinner and tried to get some sleep.
Getting up (before the alarm) went back to the camera. Thank goodness for the handheld gps. Even with the torchlight it would have been difficult to get to the camera without it.
First test shot was okay – I did a few single frame shots showing a lot of airglow. A major part of the visualisations for tonight was to emphasise the textures of the salt lake pressure ridges and the scale of the milky way. A lot of self portraits
Getting to work – my visualisation for the scene was:
- Scale – “Space is big. You just won’t believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it’s a long way down the road to the drug store, but that’s just peanuts to space.” – Douglas Adams. It’s important to try to make it look big. Therefore it should look expansive across the frame and also make myself look small. Knowing the wide angle lens and how it’s going to stitch together, I had a fair idea of how far I needed to get away from the camera.
- Textures – I wanted to emphasise the textures in the salt lake. If I relied on star light, they would be present, but quite flat. So my preference is to either use crescent moon light or artificially create it with flash. Creating it myself means I have very tight control over it. Using a lot of flash, can use modifiers to change the characteristics of the light – it’s direction, colour, intensity etc. I used the lightsphere as normal to spread it in a nice pattern around me. In this instance I decided that for at least one panorama I would use a gel and used a CTO. This reduced the light – so increased the power to compensate. Having seen the green airglow – I did consider using complementary colours (red), however while it would look more like a martian landscape then, I felt it really would look less natural then.
Apart from the above:
- I also observed the surroundings and placed the flash and myself close to one of the sources of light pollution to see if I can use that to enhance rather than being another point where the eye is attracted to and distracting from the key elements.
- Balance – between the self portrait and the milky way core.
- I’ve more or less got a standard gear for this. Ultimately self portraits like this is portraiture, so elements still have to be considered like pose and attire. I’ve generally been wearing my hiking boots, hiking pants, waist bag (with gps and other things), weather jacket and head lamp. I could perhaps carry a pack as well – that would also emphasise the explorer aspect. Stance is also a consideration – I generally take a few shots with slightly different poses and with different shadows for effect.
The panorama was 27 images taken immediately sequentially at ISO 6400 F2.8 25s at 16mm. I did manage a few more panoramas that night.
In post processing, the image was easy – the frames came together quite easily (maybe the benefit of moving it only 15 degrees each time rather than 30 degrees – in which case the distortion makes it harder for the software to pick the control points). I masked the sky to the land for slightly different treatment. The land I did curves and colour temperature. For the sky I did some masking with curves and colour temperature and did some localised contrast adjustments and removed one artificial light source. The curves affects the saturation and I didn’t want to over do it. I ran topaz denoise on the scene. Then into lightroom and did a couple of brush adjustments and more noise control but avoided doing too much else to it. In LR I tend to do just fine refinements at that time. I didn’t want to process it too much and like to have a “natural” feel to it.