Photograph the Milky Way: Part Two

Previously on the Eloquent Nature blog: Photograph the Milky Way: Part One

Viewing the Milky Way requires nothing more than a clear, dark sky. The Milky Way’s luminosity is fixed, so our ability to see it is largely a function of the darkness of the surrounding sky—the darker the sky, the better the Milky Way stands out. But because our eyes can only take in a fixed amount of light, there’s a ceiling on our ability to view the Milky Way with the unaided eye.

A camera, on the other hand, can accumulate light for a virtually unlimited duration. This, combined with technological advances that continue increasing the light sensitivity of digital sensors, means that when it comes to photographing the Milky Way, well…, the sky’s the limit. As glorious as it is to view the Milky Way with the unaided eye, a camera will show you things your eyes can’t see. In fact, not only does the right camera in the right hands resolve far more Milky Way detail than we can see, it also reveals color too faint for the human eye.

Knowing when and where to view the Milky Way is a great start, but photographing the Milky Way requires a combination of equipment, skill, and experience that doesn’t just happen overnight (so to speak). But Milky Way photography doesn’t need to break the bank, and it’s not rocket science.

Equipment

Bottom line, photographing the Milky Way is all about maximizing your ability to collect light: long exposures, fast lenses, high ISO.

Camera

In general, the larger your camera’s sensor and photosites (the “pixels” that capture the light), the more efficiently it collects light. Because other technology is involved, there’s not an absolute correlation between sensor and pixel size and light gathering capability, but a small, densely packed sensor almost certainly rules out your smartphone and point-and-shoot cameras anything more than a fuzzy snap of the Milky Way. At the very least you’ll want a mirrorless or DSLR camera with an APS-C (1.5/1.6 crop) size sensor. Better still is a full frame mirrorless or DSLR camera. (A 4/3 Olympus or Panasonic sensor might work, but I’ve not been overly impressed with the high ISO images I’ve seen from these smaller sensors.)

Another general rule is that the newer the technology, the better it will perform in low light. Even with their smaller, more densely packed sensors, many of today’s top APS-C bodies outperform in low light full frame bodies that have been out for a few years, so full frame or APS-C, if your camera is relatively new, it will probably do the job.

If you’re shopping for a new camera and think night photography might be in your future, compare your potential cameras’ high ISO capabilities—not their maximum ISO, but read some reviews to see how your camera candidates fare in objective tests by credible sources like DP Review or Imaging Resource (there are many others).

An often overlooked consideration is the camera’s ability to focus in extreme low light. Autofocusing on the stars or landscape will be difficult to impossible, and you’ll not be able to see well enough through a DSLR’s viewfinder to manually focus. Some bodies with a fast lens will autofocus on a bright star or planet, but it’s not something I’d count on (though I expect within a few years before this capability becomes more common).

Having photographed for years with Sony and Canon, and working extensively with most other mirrorless and DSLR bodies in my workshops, I have lots of experience with cameras from many manufacturers. In my book, focus peaking makes mirrorless the clear winner for night focusing. Sony’s current mirrorless bodies (a7R II, a7S, and a7S II) are by far the easiest I’ve ever used for focusing in the dark—what took a minute or more with my Canon, I can do in seconds using focus peaking with my Sony bodies. That said, of the major DSLR brands, I’ve found Canon’s superior LCD screen makes it much easier to focus in extreme low light than Nikon. (More on focus later.)

Lens

Put simply, to photograph the Milky Way you want fast, wide glass—the faster the better. Fast to capture as much light as possible; wide to take in lots of sky. A faster lens also makes focus and composition easier because its larger aperture gathers more light. How fast? F/2.8 or faster—preferably faster. How wide? At least 28mm, and 24mm or wider is better still. I do enough night photography that I have a dedicated, night-only lens—my original night lens was a Canon-mount Zeiss 28mm f/2; my current night lens is a Rokinon 24mm f/1.4.

Tripod

It goes without saying that at exposure times up to 30 seconds, you’ll need a sturdy tripod and head for Milky Way photography. You don’t need to spend a fortune, but the more you spend, the happier you’ll be in the long run (trust me). Carbon fiber provides the best combination of strength, vibration reduction, and light weight, but a sturdy (heavy) aluminum tripod will do the job.

An extended centerpost is not terribly stable, and a non-extended centerpost limits your ability to spread the tripod’s legs and get low, so I avoid tripods with a centerpost. But if you have a sturdy tripod with a centerpost, don’t run out and purchase a new one—just don’t extend the centerpost when photographing at night.

Read my tips for purchasing a tripod here.

Other stuff

To eliminate the possibility of camera vibration I recommend a remote release; without a remote you’ll risk annoying all within earshot with your camera’s 2-second timer beep. Don’t forget a flashlight or headlamp for the walk to and from the car. And it’s never a bad idea to toss an extra battery in your pocket.

Getting the shot

Keep it simple

There are just so many things that can go wrong on a moonless night when there’s not enough light to see camera controls, the contents of your bag, and the tripod leg you’re about to trip over. After doing this for many years, both on my own and helping others in workshops, I’ve decided that simplicity is essential.

Simplicity starts with paring down to the absolute minimum gear: a sturdy tripod, one body, one lens, and a remote release (plus an extra battery in my pocket). Everything else stays at home, in the car, or if I’m staying out after a sunset shoot, in my bag.

Upon arrival at my night photography destination, I extract my tripod, camera, lens (don’t forget to remove the polarizer), and remote release. I connect the remote and mount my lens—if it’s a zoom I set the focal length at the lens’s widest—then set my exposure and focus (more on exposure and focus below). If I’m walking to my photo site, I carry the pre-exposed and focused camera on the tripod (I know this makes some people uncomfortable, but if you don’t trust your head enough to hold onto your camera while you’re walking, it’s time for a new head), trying to keep the tripod as upright and stable as possible as I walk.

Flashlights/headlamps are essential for the walk/hike out to to and from my shooting location, but while I’m there and in shoot mode, it’s no flashlights, no exceptions. This is particularly important when I’m with a group. Not only does a flashlight inhibit your night vision, its light leaks into the frame of everyone who’s there. And while red lights may be better for your night vision, they’re particularly insidious about leaking into everyone’s frame (so before you ask, no red light!). If you follow my no flashlight rule, you’ll be amazed at how well your eyes adjust. I can operate my camera’s controls in the dark—it’s not hard with a little practice, and well worth the effort to learn. If I ever do need to see my camera to adjust something, or if I need to see to move around, my cell phone screen (not the phone’s flashlight, just its screen) gives me all the light I need.

Composition

A good Milky Way image is distinguished from an ordinary Milky Way image by its foreground. Simply finding a location that’s dark enough to see the Milky Way is difficult enough; finding a dark location that also has a foreground worthy of pairing with the Milky Way usually takes a little planning.

Since the Milky Way’s center is in the southern sky (for Northern Hemisphere observers), I look for remote (away from light pollution) subjects that I can photograph while facing south. Keep in mind that unless you have a ridiculous light gathering camera (like the Sony a7S or a7S II) and an extremely fast lens (f/2 or faster), your foreground will probably be more dark shape than detail. Water’s inherent reflectivity makes it a good foreground subject as well, especially if the water includes rocks or other features to add a little visual weight.

When I encounter a scene I deem photo worthy, not only do I try to determine its best light and moon rise/set possibilities, I also consider its potential as a Milky Way subject. Can I align it with the southern sky? Are there strong subjects that stand out against the sky? Is there any water I can include in my frame?

I’ve found views of the Grand Canyon from the North Rim, the Kilauea Caldera, and the bristlecone pines in California’s White Mountains that work spectacularly. On the other hand, while Yosemite Valley has lots to love, you don’t see a lot of Milky Way images from Yosemite Valley because there just aren’t that many south views there, and Yosemite’s towering, east/west trending granite walls give its south views an extremely high horizon that blocks much of the galactic core from the valley floor.

To maximize the amount of Milky Way in my frame, I generally (but not always) start with a vertical orientation that’s at least 2/3 sky. On the other hand, I do make sure to give myself more options with a few horizontal compositions as well. Given the near total darkness required of a Milky Way shoot, it’s often too dark to see well enough to compose that scene. If I can’t see well enough to compose I guess at a composition, take a short test exposure at an extreme (unusable) ISO to enable a relatively fast shutter speed (a few seconds), adjust the composition based on the image in the LCD, and repeat until I’m satisfied.

Focus

Needless to say, when it’s dark enough to view the Milky Way, there’s not enough light to autofocus (unless you have a rare camera/lens combo that can autofocus on a bright star and planet), or even to manually focus with confidence. And of all the things that can ruin a Milky Way image (not to mention an entire night), poor focus is number one. Not only is achieving focus difficult, it’s very easy to think you’re focused only to discover later that you just missed.

Because the Milky Way’s focus point is infinity, and you almost certainly won’t have enough light to stop down for more depth of field, your closest foreground subjects should be far enough away to be sharp when you’re wide open and focused at infinity. Before going out to shoot, find a hyperfocal app and plug in the values for your camera and lens at its widest aperture. Even though it’s technically possible to be sharp from half the hyperfocal distance to infinity, the kind of precise focus this requires is difficult to impossible in the dark, so my rule of thumb is to make sure my closest subject is no closer than the hyperfocal distance.

For example, I know with my Rokinon 24mm f/1.4 wide open on my full frame Sony a7S II, the hyperfocal distance is about 50 feet. If I have a subject that’s closer (such as a bristlecone pine), I’ll pre-focus (before dark) on the hyperfocal distance, or shine a bright light on an object at the hyperfocal distance and focus there, but generally I make sure everything is at least 50 feet away. Read more about hyperfocal focus in my Depth of Field article.

By far the number one cause of night focus misses is the idea that you can just dial any lens to infinity; followed closely by the idea that focused at one focal length means focused at all focal lengths. Because when it comes to sharpness, almost isn’t good enough, if you have a zoom lens, don’t even think of trying to dial the focus ring to the end for infinity. And even for most prime lenses, the infinity point is a little short of all the way to the end, and can vary slightly with the temperature and f-stop. If you know your lens well enough to be certain of its infinity point by feel (and are a risk taker), go for it. And that zoom lens that claims to be parfocal? While it’s possible that your zoom will hold focus throughout its entire focal range, regardless of what the manufacturer claims, I wouldn’t bet an entire shoot on it without testing first.

All this means that the only way to ensure night photography sharpness is to focus carefully on something before shooting, refocus every time your focal length changes, and check focus frequently by displaying and magnifying an image on your LCD. To simplify (there’s that word again), when using a zoom lens, I usually set the lens at its widest focal length, focus, verify, then never change the focal length again once I know I’m focused. And remember, the best way to ensure focus is to set your focal length and focus before it gets dark.

But sometimes pre-focusing isn’t possible, or for some reason you need to refocus after darkness falls. If I arrive at my destination in the dark, I autofocus on my headlights, a bright flashlight, or a laser 50 feet or more away. And again, never assume you’re sharp—always magnify your image and check it after you focus.

For more on focusing in the dark, including how to use stars to focus, read my Starlight Photo Tips article.

Exposure

Exposing a Milky Way image is wonderfully simple once you realize that you don’t have to meter because you can’t (not enough light)—your goal is simply to capture as many photons as you can without damaging the image with noise, star motion, and lens flaws.

Basically, you can’t give a Milky Way image too much light. What I mean by that is, capturing the amount of light required to overexpose a Milky Way image is only possible if you’ve chosen an ISO and/or shutter speed that significantly compromises the quality of the image with excessive noise and/or star motion.

In a perfect world, I’d take every image at ISO 100 and f/8—the best ISO and f-stop for my camera and lens. But that’s not possible when photographing in near total darkness—a usable Milky Way image requires exposure compromises. What kind of compromises? Each exposure variable causes a different problem when pushed too far:

• ISO: Raising ISO to increase light sensitivity comes with a corresponding increase in noise that muddies detail. The noise at any particular ISO varies greatly with the camera, so it’s essential to know your camera’s low-light capability(!). Some of the noise can be cleaned up with noise reduction software (I use Topaz DeNoise 6)—the amount that cleans up will depend on the noise reduction software you use, your skill using that software, and where the noise is (is it marring empty voids or spoiling essential detail?).
• Shutter speed: The longer the shutter stays open, the more motion blur spreads the stars’ distinct pinpoints into streaks. I’m not a big fan of formulas that dictate star photography shutter speeds because I find them arbitrary and inflexible, and they fail to account for the fact that the amount of apparent stellar motion varies with the direction you’re composing (you’ll get less motion the closer to the north or south poles you’re aimed). My general shutter-speed rule of thumb is 30-seconds or less, preferably less—I won’t exceed 30 seconds, and do everything I can to get enough light with a faster shutter speed.
• F-stop: At their widest apertures, lenses tend to lose sharpness (especially on the edges) and display optical flaws like comatic aberration (also called coma) that distorts points of light (like stars) into comet shaped blurs. For many lenses, stopping down even one stop from wide open significantly improves image quality.

Again: My approach to metering for the Milky Way is to give my scene as much light as I can without pushing the exposure compromises to a point I can’t live with. Where exactly is that point? Not only is that a subjective question that varies with each camera body, lens, and scene, as technology improves, I’m less forgiving of exposure compromises than I once was. For example, when I started photographing the Milky Way with my Canon 1DS Mark III, the Milky Way scenes I could shoot were limited because my fastest wide lens was f/4 and I got too much noise when I pushed my ISO beyond 1600. This forced me compromise by shooting wide open with a 30-second shutter speed to achieve even marginal results. In fact, given these limitations, despite trying to photograph the Milky Way from many locations, the only foreground that worked well enough was Kilauea Caldera, because it was its own light source.

Today (early 2017) I photograph the Milky Way with a Sony a7S II and a Rokinon 24mm f/1.4 lens. I get cleaner images from my Sony at ISO 6400 than got a ISO 1600 on my Canon 1DSIII, and the light gathering capability of an f/1.4 lens revelatory. Now I can stop down slightly to reduce lens aberrations, drop my shutter speed to 20 or 15 seconds to cut star motion 33-50 percent, and still get usable foreground detail by starlight.

I can’t emphasize enough how important it is to know your camera’s and lens’s capabilities in low light, and how for you’re comfortable pushing them. For each of the night photography equipment combos I’ve used, I’ve established a general exposure upper threshold, rule-of-thumb compromise points for each exposure setting that I won’t exceed until I’ve reached the compromise threshold of the other exposure settings. For example, with my a7SII/Rokinon combo, I usually start at ISO 3200, f/2, 20 seconds. Those settings will usually get me enough light for Milky Way color and a little foreground detail. But if I want more light (for example, if I’m shooting into the black pit of the Grand Canyon from the North Rim), my first exposure compromise is to increase to ISO 6400; if I decide I need even more light, my next compromise is to open up to f/1.4; if that still isn’t enough light, my next compromise is to bump my shutter speed to 30 seconds. Finally, if I want more light that ISO 6400, f/1.4, 30 seconds delivers, I’ll try ISO 12,800 (and cross my fingers)*. If that’s not enough, I go home (or just sit and enjoy the view).

These thresholds are guidelines rather than hard-and-fast rules, and they apply to my setup only—your results may vary. And even though I’m pretty secure with this workflow, for every Milky Way composition I try a variety of exposure combinations before moving to another composition. Not only does this give me a range of options to choose between when I’m at home and reviewing my images on a big monitor, it also gives me more insight into my camera/lens capabilities, allowing me to refine my exposure compromise threshold points.

* In normal situations the Sony a7SII can handle ISO 12,800 without even breathing hard, but the long exposure time required of night photography generates a lot of heat on the sensor with a corresponding increase in noise.

It’s time to click that shutter

You’re in position with the right gear, composed, focused, and exposure values set. Before you actually click the shutter, let me remind you of a couple of things you can do to ensure the best results: First, lower that center post. A tripod center post’s inherent instability is magnified during long exposures, not just by wind, but even by nearby footsteps, the press of the shutter button, and slap of the mirror (and sometimes it seems, by ghosts). And speaking of shutter clicks, you should be using a remote cable or two-second timer to eliminate the vibration imparted when your finger presses the shutter button.

When that first Milky Way image pops up on the LCD, it’s pretty exciting. So exciting in fact that sometimes you risk being lulled into a “Wow, this isn’t as hard as I expected” complacency. Even though you think everything’s perfect, don’t forget to review your image sharpness every few frames by displaying and magnifying and image on your LCD. In theory nothing should change unless you changed it, but in practice I’ve noticed a distinct inclination for focus to shift mysteriously between shots. Whether it’s slight temperature changes or an inadvertent nudge of the focus ring as you fumble with controls in the dark, you can file periodically checking your sharpness falls under “an ounce of prevention….” Believe me, this will save a lot of angst later.

And finally, don’t forget to play with different exposure settings for each composition. Not only does this give you more options, it also gives you more insight into your camera/lens combo’s low light capabilities.

The bottom line

Though having top-of-the-line low-light equipment helps a lot, it’s not essential. If you have a full frame DSLR that’s less than five years old, and a lens that’s f/2.8 or faster, you probably have all the equipment you need to get great the Milky Way images. Even with a cropped sensor, or an f/4 lens, you have a good chance of getting usable Milky Way images. If you’ve never done it before, don’t expect perfection the first time out. What you can expect is improvement each time you go out as you learn the limitations of your equipment and identify your own exposure compromise thresholds. And success or failure, at the very least you’ll have spent a magnificent night under the stars.