Oh, What a Night…

Gary Hart Photography: Dark Sky Dreams, Lake Matheson, New Zealand

Dark Sky, Lake Matheson, New Zealand
Sony a7S II
Rokinon 24mm f/1.4
30 seconds
F/1.4
ISO 12800

(Jump to the bottom for a “how-to” and my starlight photography exposure recipe)

Five photographers followed bouncing headlamps through the chilly dark. Even in midday the trail through the dense rainforest surrounding Lake Matheson has a twilight feel; on a moonless winter night like this, the path becomes downright cave-like. Soon our footsteps were in sync, each tap broken by a beat of eerie silence. For me, the solitary experience at the front of the line was simultaneously serene and disconcerting, a feeling enhanced by occasional rustling and primal cries from the primitive world outside radius of my light.

I was midway through the second of back-to-back New Zealand Winter photo workshops. Just a couple of hours earlier the entire group had completed the nearly 2 1/2 mile loop in daylight. So striking was the sunset reflection of Mt. Tasman and Mt. Cook on that hike, that when we looked up after dinner and saw stars, a few of us hardcore night shooters couldn’t resist returning to the lake to photograph the Milky Way above the peaks.

Rather than hike all the way out there, we reasoned that we could satisfy our objective with a relatively short walk to Jetty Viewpoint, the closest view of the lake and mountains, less than a quarter of the way along the loop. Given the spur-of-the-moment nature of our adventure, I hadn’t done my usual (obsessive) plotting of the Milky Way’s position before bundling up and heading our to the lake. I knew only that it would be more or less vertical, in the general direction of the peaks.

What I hadn’t fully accounted for is how much higher in the sky as the Milky Way is in New Zealand. So unfortunately, by the time the five of us arrived at Jetty Viewpoint, we found the Milky Way was so high that capturing the bright galactic core and its reflection required a vertical composition. And it had rotated so far north that including the Milky Way and the peaks required a horizontal composition. After trying a few versions of those either/or compositions, we decided that since the reflection was the real star of the show, we may as well just continue another 20 minutes to the Lake Matheson’s best view point, Reflection Island.

The shear volume of stars in the pure New Zealand darkness is mesmerizing, but it’s disorienting to look up at night and not see a single familiar constellation, . Once we were settled in at Reflection Island, I spent the time during exposures wandering my gaze about the foreign sky.

A camera can “see” much better in the dark than we can, a capability that only continues to improve. For many years my night photography was limited by technology to moonlight only, but the low-light capability of the newest cameras has opened the door to a world that’s been invisible to the naked eye. Combining a modern camera that captures clean high ISO images with a fast lens not only enables moonless night photography, it pulls unseen wonders from the darkness.

I only use my Sony a7SII and Rokinon 24mm f/1.4 lens when photographing extreme dark skies, but when I do, I never cease to be blown away by what they “see.” Packing for four weeks in winter without exceeding the airline’s weight limits is difficult. But anticipating the opportunity to photograph the Southern Hemisphere night sky, I bit the bullet and added my dedicated night photography gear to my camera bag. Every time an exposure completed, I couldn’t take my eyes off the image on my LCD. As saturated with stars as the sky appeared, each image revealed far more stars than were visible to my eyes, and the brightest stars stood out like an approaching locomotive.

A quick check of my astronomy app told me that the bright star burning a hole in the sky above the trees on the right is Achernar, well known Down Under but new to me. Slightly brighter than magnitiude .5 (the lower the number, the brighter the star), it’s the ninth brightest star in the night sky—the Achernar photons that landed on my sensor started their Earthward journey nearly 140 years ago.

The Magellanic Clouds (satellite galaxies gravitationally bound to the Milky Way but not visible in the Northern Hemisphere) that were faint fuzzy blurs to my eyes took on actual shapes. And while I couldn’t fit the mountains and both of the Magellanic Clouds in my frame, I was able to included the Small Magellanic Cloud in this image.

More exciting than the volume of stars revealed by my camera was the spectacular reflection it pulled from the seemingly black void of the lake’s surface. This ability to view beauty hidden from my eyes by darkness is the best part of night photography.

Starlight exposure made simple

Based on many years experience teaching starlight photography (not to be confused with moonlight photography), I’ve come up with what I think is the simplest approach to the most frequently asked night photography question: “What exposure settings should I use?”

The problem is, there isn’t a single set of ISO, f-stop, and shutter speed settings you can plug in for great results because the setting you use (and the results you get) depend on your equipment. Starlight photography is all about capturing light, the more the better. But as good as today’s camera technology is, successful night photography is still about making compromises. As you try to maximize the light reaching your sensor, you’ll need to manage these exposure compromises:

Shutter speed: Star motion is a function of the time the shutter is open, the focal length, and the direction your lens points—the faster the shutter speed, wider the lens, and closer to the poles (due north or south) you’re composed, the less star motion you’ll record. As much as we like pinpoint stars, I’ve always felt that getting enough light is more important than perfect pinpoints. Your compromise comes as you try to decide how much motion you can live with. My drop-dead shutter speed that I won’t exceed is 30 seconds.
F-stop: Sharpness and distortion, especially on the edges, becomes a concern when any lens is wide open. With some lenses it’s a livable problem, with others you’ll probably want to stop-down a stop or two. A starlight f-stop rule of thumb I follow is that (assuming a current camera with good high ISO capability) at f/4, the best you’ll be able to hope for is silhouettes; at f/2.8, you can probably get decent but dark landscape detail; making the scene significantly brighter than your eyes see (like this image) usually requires f/2 or faster. Given that, I like to shoot starlight at f/1.4 (hence my dedicated night lenses), and just live with slightly less than perfect quality in the corners.
ISO: Noise is the threshold that most limits our night efforts. If we didn’t have to deal with noise, we could push our ISO as far as necessary to eliminate star motion and lens flaws. High ISO noise varies a lot with the camera—some cameras struggle mightily beyond ISO 1600, others deliver very usable results at ISO 12800 or even higher. As a general rule, the larger the sensor, and the fewer the megapixels, the better the high ISO performance (larger, farther apart photosites mean more light gathering and less heat). So an APS-C sensor will usually yield cleaner high ISO images than a 4/3 sensor (Olympus and Panasonic), and a full frame sensor will yield cleaner high ISO images than an APS-C sensor. This is by no means an absolute—today’s 40+ megapixel sensors are much better at high ISOs than yesterday’s 12 megapixel sensors, and some of today’s high resolution sensors (for example, the Sony a7RIII) are far superior to contemporary sensors with lower resolution. My night camera is the 12 megapixel Sony a7SII. Regardless of the camera, and I can’t emphasize this too much, is to know your camera and how far you can push your ISO and still yield usable results. One more thing: because high ISO performance decreases significantly with shutter speed, base your high ISO evaluations on long shutter speeds, 15-30 seconds.

Understanding these compromises, you’re ready for my starlight-exposure-made-simple axiom: Give the scene as much light as you can without ruining the image. In other words, for the most light possible, use the longest shutter speed, widest aperture, and highest ISO that gives you results you can live with.

Taking this approach doesn’t mean that I don’t vary my exposure settings. Once I’ve settled on a composition, I use a variety exposure-setting combinations. Not only does this give me as many options as possible at processing time, it’s also an opportunity better understand my cameras’ and lenses’ limitations to learn how far I can push the exposure threshold next time.