Capturing Clouds of Light: How to Photograph the Aurora Borealis

I recently led a few photo tours to Iceland to photograph the northern lights, and our groups each had the good fortune to experience several nights of clear skies and brilliant displays of aurora.

It's an amazing experience, both to photograph and simply to see. One of the high seasons for aurora is nearly upon us, so I chose to write a primer on how to tackle this exciting genre of night photography.

Where and When to Find Aurora

The aurora borealis, as the northern lights are also known, occurs when electrically charged particles from the sun are carried by solar wind toward Earth and collide with gases in the upper atmosphere. Those gas particles—most commonly oxygen (green aurora) and nitrogen (pink aurora)—are “excited” by the collisions, and release photons of light.

Earth’s magnetic field deflects most of the solar particles, but that field is weakest at the poles. This is why the aurora is mainly seen near the polar regions. (Toward the South Pole, they're called the aurora australis, or southern lights.) In general, the chances of viewing the aurora are best at latitudes above 55° N, and between the months of September and March. Historically, March and October are the best months for aurora viewing. There are a number of apps to help locate the aurora, the one we here at NPAN have used the most is Aurora Forecast. Some of the newer apps seem to have more favorable reviews, and may be worth trying. Whichever app you choose, set the preferences to send you an alert for a kp rating of 5 or higher, for middle latitudes if you live at or below 55° N latitude, and high latitudes above 55°. Kp is the unit of measurement for geomagnetic conditions responsible for the aurora.

Aurora and sodium-vapor, Reykjavik, Iceland. 20 seconds, f/4, ISO 2500.

Aurora and sodium-vapor, Reykjavik, Iceland. 20 seconds, f/4, ISO 2500.

The frequency of clear skies is also a big a factor in seeing the aurora, but broken cloud cover can add a lot of visual interest in aurora photographs. The phenomenon can appear at any time when the sky is dark, but the best viewing times are typically from 10 p.m. to 2 a.m.

Solar activity peaks and falls on an 11-year cycle. The winter of 2012-13 was the peak of the current cycle, which was theoretically the best chance to see auroral activity for the next decade. Luckily for us though, there has been plenty of auroral activity every winter since 2012.

Iceland lies between 64° and 66° N, and is ideally suited for viewing and photographing the aurora. Despite being so far north, its position on the Gulf Stream keeps the winters relatively mild compared to other good aurora viewing places such as Scandinavia and Alaska. During my two Iceland tours in 2015, we had good viewing conditions and good sightings for nine out of 17 nights, and really spectacular displays on three of those nights.

Photographing the aurora is relatively straight-forward once you understand the basics. The remainder of this article is intended to provide the basic information required for aurora photography.

Prepare for the Cold

It’s obvious that you’ll be photographing in cold weather conditions, and there are a few things you can do to protect yourself and your equipment from the cold.

Warming hut. 20 seconds, f/5.6, ISO 3200.

Warming hut. 20 seconds, f/5.6, ISO 3200.

Dress in layers, making sure that your innermost layer is synthetic rather than cotton. Synthetic fibers wick moisture away from the body, keeping you warm and dry. Dress as if it will be colder than it really will be. Standing around for hours on end will make you feel much colder than if you were active or if you were outside for only a short while.

Your best options are:

  • heavyweight merino wool and synthetic-blend socks
  • insulated boots with wool or sheepskin liners
  • long underwear
  • lined pants, wind pants or long underwear with ski pants

Make sure your neck is covered, and find just the right hat. The best bet for your hands is flip-top mittens with chemical hand warmers and potentially thin, form-fitting glove liners. (We particularly like the Trigger Mitt by our friends at Vallerret.) If you’re going to Alaska, or somewhere frigid, extreme cold weather clothing can be expensive, but is essential.

Camera gear for Aurora Photography

Photographing the aurora tests the limits of our equipment, so this is a case where using the best equipment possible really makes a difference in the quality of your images.

Cameras and Lenses

Cameras with full-frame sensors are ideal, as are fast, ultrawide-angle lenses. Cameras such as the or D750, Pentax K1, Sony A7R2 or A7S2, and Canon EOS 6D or EOS 5D Mark IV are particularly well-suited to this work. The next best option is an APS-C camera, such as the Nikon D500 . If you will be using an SPSC sensor camera, I recommend sticking with newer models that perform better at high ISOs.

Fast, wide to ultrawide angle lenses in the 14mm to 24mm range are the most useful for full-frame cameras, and those manufactured by Samyang under the brand names of Samyang, Bower and Rokinon offer a great value for about one-third the price of the comparable Canon and Nikon lenses, and they suffer less from coma at wide apertures. It’s recommended to test these lenses thoroughly after purchase, as quality control is notoriously inconsistent.

The best zoom lenses for this type of photography are the Tamron 15-30mm f/2.8 and Nikon 14-24mm f/2.8. As previously mentioned, a lens hood is helpful not only in preventing flare, but also for protecting the lens from frost and condensation.

Wellhead and aurora. 30 seconds, f/4, ISO 3200.

Wellhead and aurora. 30 seconds, f/4, ISO 3200.

Tripods

A sturdy tripod is essential of course, and those with three leg sections are generally more stable than those with four or five. One exception to the three section leg rule is the Gitzo Series One Traveler. This is one of our favorite travel tripods, as it packs small and is incredibly sturdy. A more economical alternative is the Manfrotto 190Go! Carbon Fiber Tripod Kit with Ball Head.

Insulated leg sections are easier to handle, especially on aluminum tripods. Ball heads are better suited for this work than traditional pan-tilt heads because they can be adjusted quickly to track quickly changing aurora.

Miscellaneous Gear

Since exposures are generally 30 seconds or less, a remote release or intervalometer is helpful, though not required. In fact, the cables can freeze and break in extremely cold weather, so if the temperature is below zero F, you’re better off without one. If you are working without a remote release of some sort, be sure to use the 2-second delay on the self-timer to avoid camera movement when depressing the shutter button.

The only other equipment you’ll need is an extra camera battery or two. You’ll want to keep your extra batteries close to your body in an inner pocket, as they will not last as long in the cold. You can also consider connecting to an external power supply with the Tether Tools Case Relay Camera Power System.

Remove any filters from your lenses, and be sure to use your lens hoods, which will help minimize frost or condensation buildup on the front element. A neoprene beer/soda cozy with the end cut off can be used to hold one or two chemical warmers to your lens, which also can prevent the lens from fogging over.

Lastly, you'll want some flashlights. We recommend carrying at least two: a dim or preferably red one (such as Coast's FL57 headlamp) for finding things in your bag or making adjustments to your camera, and a very bright flashlight to use as a focusing aid or for light painting (as usual, we can't recommend the Coast HP7R enough). Use the coupon code parksatnight for 25% off of all merchandise at CoastPortland.com.

Ambient Light and Aurora Photography

Ambient light from towns and cities will obscure all but the brightest aurora displays, so make sure you are well away from urban areas. That said, the distant glow from streetlights or the last glow of a fading sunset on the horizon can add another element of color to your photographs. Sodium-vapor streetlights reflecting off of low clouds is another possibility to add contrasting color to aurora photos.

Aurora and sodium-vapor clouds. 20 seconds, f/3.5, ISO 3200.

Aurora and sodium-vapor clouds. 20 seconds, f/3.5, ISO 3200.

Lunar phase and lunar elevation in the sky both have a profound impact on night photography in general, and on aurora photography in particular. Photographing without any moonlight will mean primarily silhouetted foregrounds, and longer exposures at higher ISOs. Photographing under a full moon will mean much brighter foregrounds (especially if there is snow on the ground), shorter exposures at lower ISOs and fainter aurora in your photographs.

You can photograph the aurora at all phases of the lunar cycle, and the results will vary fairly dramatically; it’s just a matter of what kind of images you are looking for. My preference is to photograph between the first quarter and waxing gibbous phases, as there is sufficient moonlight to illuminate the landscape without overpowering the aurora. The first quarter moon rises around noon, sets around midnight, and then rises about 45 minutes later each day until it is full. The full moon rises at about sunset and sets at about sunrise.

If you include interesting foreground elements, you may want to add light painting, especially when there is little or no moonlight present.

Camera Settings and Exposure for Aurora Photography

Aurora photography pushes the limits of even today’s best DSLR cameras. Because of the low light levels, and the need to keep exposures relatively short due to the moving nature of the aurora, you’ll be photographing at the highest usable ISO of your camera and the widest aperture that will yield sufficient sharpness and depth of field.

Determining your highest usable ISO is simply a matter of testing your camera by making a series of low-light exposures at increasing ISOs, and then scrutinizing the shadow areas of each exposure, preferably by making final-size prints of the images. (We will detail more about how to do this in a future blog post.) For me, 1600 is the highest ISO I use for print-quality images and 6400 for web-quality with my 5D Mark II.

Similarly, you’ll want to test your lenses for coma at wide apertures. A form of optical distortion, coma causes stars to appear as if they have “tails” like a comet, or sometimes like a bird in flight. Test your lenses by shooting starry skies at maximum aperture and then stopping down in half- or third-stop increments until you get to f/5.6, and then looking at the resulting images at full magnification for signs of coma. It’s generally found near the edges of the frame in images shot at or near maximum aperture. The Canon and Nikon 24mm f/1.4 lenses both suffer from fairly severe coma problems. (Coma is another topic we will discuss in more detail in the future.)

Aurora photography pushes the limits of even today’s best DSLR cameras.

Exposures for aurora photography range from approximately 30 seconds, f/2.8, ISO 6400 for faint to average aurora on a moonless night, to 4 seconds, f4, ISO 800 for bright coronal aurora on a full-moon night. The intensity of the aurora can vary dramatically—sometimes it’s barely visible to the naked eye but shows up nicely in photographs, and sometimes it can be so bright as to illuminate the landscape.

Determining exposure is accomplished by viewing a combination of the RGB histogram and the blinking highlight indicator. At a minimum, you should have a histogram that shows no shadow clipping—it can be a left-biased histogram, but the histogram should not be touching the left edge of the graph. Images with more exposure will have cleaner shadows with less noise. Ideally, you should not have to lighten your image in post-processing. Use the blinking highlight indicator to make sure that you are not overexposing the aurora or any highlights created by light painting. Use the LCD image preview primarily for confirming composition and focus.

Key camera settings

Here’s a rundown of the camera settings most important to photographing aurora, and my recommendations for how to set them.

  • Set file quality to RAW.
  • Use your camera’s highest usable ISO setting, hopefully between 1600 and 6400.
  • Set white balance to between 3700 K and 4100 K when shooting under moonlight, or between 4000 K and 5500 K when there is no moon.
  • Set your camera’s Long Exposure Noise Reduction (LENR) to Auto (if available) or on.
  • Enable your camera’s RGB histogram to use as the primary exposure determinant in natural light.
  • Enable the blinking highlight indicator to use to ensure that you do not clip the aurora.
  • Set the LCD brightness to “auto” or reduce it manually to almost the lowest setting.
  • Set exposure mode to Manual.
  • Set focus to Manual.
  • Turn off IS/VR lens functions
  • For focusing, use magnified Live View with the assistance of a flashlight to illuminate your focal subject, or use conservative, well-executed hyperfocal distance.

For more information and a complete list of camera settings, download my PDF “Basic Camera Settings for Milky Way and Aurora Photography.”

Getting Out There

As with any type of photography, you’ll get better results with experience and practice. It’s very helpful to have a basic understanding of night photography, and to be completely familiar with your equipment before departing toward the poles. Simply working in the cold and darkness complicates photography exponentially, so do your homework, and be prepared. Don’t expect to get perfect results on your first attempt.

Taking a moment to enjoy the aurora.

Taking a moment to enjoy the aurora.

Photographing the northern lights can be like photographing a close friend or family member’s wedding: You’re so focused on the task at hand that before you know it, the event is over and you’ve completely missed out on the experience! Make sure that you take some time to simply step back, look up, and enjoy the magnificence of this special phenomenon.

National Parks at Night's 2017 Iceland Photo Tour is sold out, but there are at least a half a dozen US National Parks with opportunities Aurora Borealis, (and a few national parks in Iceland that we won't get to on this year's trip) so be sure that you are signed up for our mailing list to get early notification of our 2018 workshops and tours.

Lance Keimig has been photographing at night for 30 years, and is the author of Night Photography and Light Painting: Finding Your Way in the Dark (Focal Press, 2015). Learn more about his images and workshops at www.thenightskye.com.

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Level Up With Light Painting: Correcting the Color of Your Flashlight (Part II)

In my last post on flashlight color I demonstrated how LED flashlights produce a cooler light than I prefer. I went on to show you how to analyze and correct the color using simple gels from the Roscolux Swatchbook.

In that post, the filtration I worked out for my favorite flashlights—the Coast 300-lumen Coast HP7R and 185-lumen Coast HP5R—was a Roscolux 1/2 CTO combined with a 1/8 minus green. This combination works well when my Nikon’s white balance is set to Direct Sun (Daylight on a Canon). Night photography, however, often requires a significant deviation from our common white balance settings.

Finding the Fix

Direct Sun white balance has an approximate Kelvin temperature of 5500. Although, as I mentioned in my last post, Lightroom may display your Kelvin temperature higher or lower depending on Adobe’s interpretation of your camera. Adobe interprets my Nikon’s D4s’s white balance as 4900 K. For the remainder of this post I’ll refer to the Kelvin setting on the camera rather than Adobe’s interpretation.

When using the Direct Sun white balance setting, subjects photographed under average midday sunlight will be rendered properly with regard to color. If, however, your white balance is set to Direct Sun and you photograph a subject under a different light source, the subject will take on the color cast of that light source. For example, for the photo in Figure 1, I kept my camera set to Direct Sun white balance while photographing under the heavy orange cast of the sign lights. Figure 2 shows the color-corrected version at 2000 K.

Figure 1. 5500 K (Direct Sun) white balance

Figure 2. 2000 K white balance

Lowering that white balance had the effect of adding in a blue cast, counteracting the orange/yellow cast it had before. Now imagine if I had used my somewhat blue LED flashlight to paint the people in the foreground. After color correction, the subjects illuminated by the flashlight would be even more blue due to the lower Kelvin temperature.

So while the filter combination I used for my flashlight worked well with Direct Sun white balance, that same filter combinations would turn the flashlight light to blue when using white balance settings typical of night photography.

Finding the Filters

How to resolve this issue? Once again I turned to my X-Rite ColorChecker chart for my visual tests. I began by setting my camera’s white balance to Tungsten, which is roughly 3200 K. This is a setting I often use for night photography. Next I light-painted the chart with my standard filtration of 1/2 CTO combined with a 1/8 minus green. This produced the color in Figure 3.

Figure 3. 3200 K white balance, Coast HP7R filtered with Rosco 1/2 CTO and 1/8 minus green filter gels

Figure 3. 3200 K white balance, Coast HP7R filtered with Rosco 1/2 CTO and 1/8 minus green filter gels

The chart is noticeably cool due to the lowered white balance setting of 3200 K. So I experimented with a variety of gels, looking for the right mix to produce a more accurate color balance. After experimenting, I settled on a Roscolux Dark Bastard Amber, which when added to my 1/2 CTO and 1/8 minus green, produced the effect we see in Figure 4.

Figure 4. 3200 K white balance, Coast HP7R filtered with Rosco 1/2 CTO and 1/8 minus green plus Dark Bastard Orange filter gels.

Figure 4. 3200 K white balance, Coast HP7R filtered with Rosco 1/2 CTO and 1/8 minus green plus Dark Bastard Orange filter gels.

You can see that new combination of filters has produce a color cast that is neutral to slightly warm when shooting with Tungsten white balance.

Putting This Into Practice

For the last step, I took a new clear plastic filter from a Coast LF100 filter kit and again traced and cut out a 1/2 CTO, a 1/8 minus green and a Dark Bastard Orange, and taped them all to the filter. Now I can easily interchange the two plastic filters (one with my original gel combo and the second with the original combo plus Dark Bastard Orange) when I change my white balance from Direct Sun to a Tungsten.

Figures 5 through 8 show a real-world example of how this affects the color of a scene. In Figure 5, my camera’s Direct Sun white balance produces an overly orange image due to the sodium vapor lights (common in most city lighting) illuminating the building.

Figure 5. Direct Sun white balance

Figure 5. Direct Sun white balance

Figure 6 shows the same scene after I changed my camera’s white balance to Tungsten (3200K). Notice the nearly neutral color of the metal and white door.

Figure 6. Tungsten white balance

Figure 6. Tungsten white balance

For Figure 7 I kept the white balance set to Tungsten and illuminated the door with my unfiltered flashlight. The door becomes very blue due to the cooler white balance setting.

Figure 7. Tungsten white balance with unfiltered flashlight illumination

Figure 7. Tungsten white balance with unfiltered flashlight illumination

Figure 8 shows the same scene with my camera still on the Tungsten white balance setting, but light-painted with the flashlight gelled with the 1/2 CTO, 1/8 minus green and Dark Bastard Orange combination.

Figure 8. Tungsten white balance with filtered flashlight illumination

Figure 8. Tungsten white balance with filtered flashlight illumination

Of course, Tungsten white balance is not the only setting I use for night photography. My night settings range from 3200 K to 5500 K, with 3800 K being the setting I use most often. So, you may ask, why did I run my test at 3200 K if use 3800 K more often? In a word, warmth. I like my flashlight illumination to be somewhat on the warm side. A gel that produces a neutral cast at 3200 K will produce a warmer cast at 3800 K. Just how I like it!

Remember, no LED flashlight will produce perfect color. But, with a little testing and experimentation, you can create your perfect color for your light-painting illumination!

Learn more techniques from Tim Cooper’s book The Magic of Light Painting, available from Peachpit.

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Game-Changer: The Best New Piece of Gear for Night Photographers

While night photography has been reaping the rewards of the continual improvement in cameras, lens, tripods and flashlights, there have been very few gadgets that have come out and revolutionized the way we approach night photography. Well, I’m here to share that the Case Relay by Tether Tools does just that. It is the best new piece of gear for night photographers.

The Case Relay gives you power, and lots of it. The constant bane for photographers—during the day or night—is running out of juice. Once I’ve got my shot all set up on the tripod for a series of long exposures, I dread having to take the camera off mid-stream just so I can replace a battery. And good luck realigning the shot!—especially during a time-lapse when you have an extensive rig set up.

The Tether Tools Case Relay Camera Power System.

The Tether Tools Case Relay Camera Power System.

With the Case Relay, you replace your regular battery with the Tether Tools Camera Coupler, which looks exactly like your battery with a cord at the end. That cord connects to the Case Relay. The other end of the Case Relay has a 6-inch USB cord that can be plugged into one of the many USB battery packs on the market.

The Case Relay isn’t just a conduit of power, but actually has its own secondary internal 1200 mAh battery built inside. This allows you to hot-swap your USB battery packs without missing a shot. When you tap into a 10,000 mAh battery—like the Tether Tools Rock Solid—you are tapping into a long night of shooting on one battery. The Rock Solid has two USB out ports, so we can also power our phones in the field!

I like adding a little grip and protection to the Rock Solid battery pack with a protective silicone case that comes in black or orange. The final ingredient that literally ties all these items together in a very organized and neat way around your tripod is the StrapMoore.

My first test of night with the Case Relay System—4 1/2 hours of shooting stars, trains and people lighting up the scene, all stacked into this one image. And I still had plenty more power to tap into.

My first test of night with the Case Relay System—4 1/2 hours of shooting stars, trains and people lighting up the scene, all stacked into this one image. And I still had plenty more power to tap into.

I’ll be transparent here: We have a sponsor relationship with Tether Tools. But I’m not plugging their product because we have a relationship; we pursued that relationship because I absolutely love this product for how it changes my approach to night photography.

We recently made a video demonstrating the unlimited power of the Case Relay during my last Bannerman Island workshop with Matt Hill. I was shooting for eight hours and … not to give away the ending … but I still had juice in the tank!

So if you are into shooting time-lapses, long star trails, or just for many hours during the day or night, I think you’ll find the Case Relay Camera Power System to be a must-have tool to bring on your shoots.

(Note: There are several components to assembling your very own Case Relay System, so to help, we have organized all the pieces you’ll need on our Gear page.)

Gabriel Biderman is a Brooklyn-based fine art and travel photographer, and author of Night Photography: From Snapshots to Great Shots (Peachpit, 2014). During the daytime hours you'll often find Gabe at one of many photo events around the world working for B&H Photo’s road marketing team. See his portfolio and workshop lineup at www.ruinism.com.

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More Parks in the Dark: Rounding Out Our 2017 Workshop Schedule

Back in September we announced the first part of our 2017 workshop calendar. We also promised that before long we'd be ready to announce even more opportunities to learn about night photography while enjoying the camaraderie of like-minded photographers under the beautiful skies of our national lands.

Well, now we're here, getting the new year started by following through on that promise. Today we're publicly releasing the details of six new 2017 night photography adventure workshops.

For our Passport Series, one is a brand new workshop in a remote and unique national park, while two are second offerings of our two most popular '17 locations. And for our Adventure Series, one new workshop is on the beautiful New England coast, one is in the mountains of California, and one represents our first international event, a night photography tour of Westfjords, Iceland.

Passport Series

Our new Passport Series workshops include a deep dive into the night skies of a national park, plus location scouting tutorials, lectures and image reviews. Plus a whole lot of camaraderie.

Dry Tortugas National Park

Joshua Tree National Park

Olympic National Park

Joshua Tree National Park, California (2nd Week)

April 21-26, 2017Joshua Tree National Park encompasses sections of two different deserts—the Mojave and the Colorado—both full of opportunities for remarkable images. We had a high demand for the first week of this workshop, so we added this second week to provide more people the opportunity to attend!

More info & registration: Joshua Tree II

Dry Tortugas National Park, Florida

July 27-30, 2017 — Live life on a boat as we explore one of the most remote national parks in the NPS. The sights on Fort Jefferson—the most ambitious and extensive coastal fortification in the United States, located in Dry Tortugas National Park—are absolute wonders to photograph. And all this in the darkest skies on the east coast, 70 miles from Key West into the Gulf of Mexico.

More info & registration: Dry Tortugas

Olympic National Park, Washington (2nd Week)

September 24-29, 2017 — Photograph on the rugged mountains, in the vibrant rainforests and along the pristine coastline of Washington state’s Olympic Peninsula, in one of the most beautiful and diverse national parks in the U.S. Our first week of Olympic sold out in just two days, so we're offering this second workshop here in this park's best season.

More info & registration: Olympic II

Adventure Series

Adventure Series workshops are forays into national monuments, private lands near national parks, and more. These workshops will generally be shorter in duration than our Passport Series, and depending on the event, may involve less time in the classroom and more time in the field having adventures.

Cape Cod National Seashore

Eastern Sierra

Westfjords, Iceland

Cape Cod National Seashore, Massachusetts (3 Spots Left!)

May 21-24, 2017 — Photograph the open sand dunes, regal lighthouses, quaint cottages and quiet seaside villages of Cape Cod National Seashore, one of the natural gems of the New England coast.

Please note that as of the morning of this blog post, only three spots remain for the Cape Cod National Seashore workshop, so if you want to go, register now!

More info & registration: Cape Cod

Westfjords of Iceland (sold out)

August 27-September 5, 2017 — This photo tour will be special in that it occurs at the end of the brief Icelandic summer. We will visit the Westfjords before the area becomes inaccessible for the winter, but late enough in the year that we might see the Aurora Borealis.

Please note that this event sold out when pre-announced to our alumni and our workshop-announcement email list. To receive early notifications of new workshops (including, hint hint, to this same country in 2018), sign up for our workshop announcements today! Alternatively, to be added to the waitlist for this photo tour in 2017, please visit the following link: Westfjords

Eastern Sierra, California

October 30-November 4, 2017 — This workshop occurs just before the full moon, and is intended primarily for photographers who are interested in light painting by moonlight. The workshop will feature three nights at the Alabama Hills in California’s Eastern Sierra, one night at the Ancient Bristlecone Pine Forest in the White Mountains, and one night photographing a mystery location.

More info & registration: Eastern Sierra

And don't miss out on ...

Cuyahoga Valley National Park

We have only three places remaining for our light-painting-intensive Passport Series workshop at Cuyahoga Valley National Park this coming May. Be sure to register today!

May 7-12, 2017: Cuyahoga Valley National Park

Cuyahoga Valley is one of the most visited national parks in the country, and also one of the most unique. It combines stunning natural scenes with rural features, such as railroad depots, farms, historic structures, covered bridges and old cemeteries, granting the photographer a nearly endless buffet of subjects to photograph at night. This will be a light-painting-intensive workshop, so ready your flashlights!

More info & registration: Cuyahoga Valley

Seize the Night

Never miss out on one of our adventures. Be one of the first to learn about our new workshops by signing up for our mailing list/workshop announcements. Plus you'll get our free ebook, Seize the Night: 20 Tips for Photographing in the Dark.

We're eager to see you out in the parks with us this year, photographing the night!

(Click here to see our entire 2017 Workshops Calendar.)

Chris Nicholson is the author of Photographing National Parks (Sidelight Books, 2015). Learn more about national parks as photography destinations, subscribe to Chris' free e-newsletter, and more at www.PhotographingNationalParks.com.

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What's the Longest Usable Shutter Speed for Astro-Landscape? (Part I)

One of the things that makes night photography rewarding and fun is that there are really no absolutes of right or wrong when it comes to exposure.

Under “normal” lighting conditions, a well-exposed image is pretty easily defined. Clean highlights, no clipped shadows, a good histogram—there are plenty of ways to evaluate exposure, and it’s usually obvious when an exposure is “correct” or “incorrect.”

But at night, exposure is much more open to interpretation. Rather than a right or wrong exposure, the photographer has more leeway to interpret the scene to their own tastes or liking. Additionally, with regard to astro-landscape photography, exposure relates to more than simply an appropriate amount of light reaching the sensor. In particular, exposure length has a profound impact on the appearance of stars in the sky.

The solution is relatively straight-forward, though the reasons and the factors that play into it are many and intertwined. But let's explore! This is the first of a two-part blog post about all the decisions and considerations that go into determining the optimal exposure for creating astro-landscape images with star points.

Workshop students in Zion National Park. This view of Checkerboard Mesa faces southeast, and shows movement in the stars that would be visible only in a very large print, or when pixel-peeping at 100 percent magnification. Nikon D750, Nikkor 24mm f/1.4 lens. 15 seconds, f/f2.8, ISO 12800.

Workshop students in Zion National Park. This view of Checkerboard Mesa faces southeast, and shows movement in the stars that would be visible only in a very large print, or when pixel-peeping at 100 percent magnification. Nikon D750, Nikkor 24mm f/1.4 lens. 15 seconds, f/f2.8, ISO 12800.

Finding the (In)Correct Exposure

One of the most frustrating aspects of night photography is that it can be difficult to establish the “correct” exposure. Yes, I just contradicted myself, and there lies the rub. Night photography is not an exact science, and trying to make it so is an exercise in futility of the highest order. There are so many variables, some of which are beyond the photographer’s control.

Attempting to “get it right” is more than science, more than art, and more than an ambiguous combination of the two. Some nocturnal imagery is more about a feeling, an atmosphere or a mood, but other images are more grounded in technical considerations. Good night photography exposures can be like Supreme Court Justice Potter Stewart’s view on pornography—you know it when you see it!

For every image, there is a set of variables that affect how long an image may be exposed before the stars appear as trails, and managing those variables is key to a successful image.

Astro-landscape imagery is a type of night photography that requires a good deal of thought and many considerations about what might be the best exposure for any given situation. Usually, determination of a photographic exposure is led by one of the exposure variables—aperture, ISO or shutter speed. One would choose a small aperture to have large depth of field. For example, you might have a subject in the foreground and stars in the background that both need to be tack sharp. Alternatively, in the case of a portrait, a large aperture that yields a shallow depth of field would usually be the better choice. In the case of an image where you know in advance that you want to make a large print, a low ISO would take priority.

In the case of astro-landscape photography, finding a shutter speed that is fast enough to record the stars as points of light rather than showing them as trails is usually the critically important variable. (Unless, of course, you want to produce star trails, but that’s a whole other issue and technique. Here we’re just talking about reproducing the look of actually being under a starry sky.)

Additionally, the combination of extremely low light levels, short shutter speeds and the need for depth of field necessitate compromise. We need to consider all three exposure variables, and the challenge is to combine them in such a way that addresses both the technical limitations and the constraints of the image.

Unhappy Trails

The stars are moving in space, but their distance from Earth makes that movement negligible in our photographs. Instead, it is the Earth’s rotation that causes long-exposure photographs of the night sky to show star “trails,” or lines of light in the sky that create a circular pattern centered over the polar axis.

Here in the Northern Hemisphere, stars appear to revolve around Polaris, or the North Star, which is centered approximately over the north polar axis. Stars in the northern sky form relatively small circles around the North Star, and stars in the eastern, western or southern skies form larger, longer star circles around Polaris.

Mesquite Sand Dunes, Death Valley National Park. This image shows the stars rotating around the North Star, and faces north-northwest. Nikon D750, Nikkor 20mm f/1.8 lens. Stacked exposures totaling 2 hours, f/3.3, ISO 400.

Mesquite Sand Dunes, Death Valley National Park. This image shows the stars rotating around the North Star, and faces north-northwest. Nikon D750, Nikkor 20mm f/1.8 lens. Stacked exposures totaling 2 hours, f/3.3, ISO 400.

For every image, there is a set of variables that affect how long an image may be exposed before the stars appear as trails, and managing those variables is key to a successful image. Accounting for those variables and weighing the pros and cons of compromising exposure, noise, depth of field and stellar movement can be a daunting task.

Many photographers attempt to scientifically calculate values for each of these variables and in turn come up with an exposure that is optimized for the conditions at hand—but this is tedious and, honestly, unnecessary. Having an understanding of the various factors that affect the appearance of stars in astro-landscape images is helpful, so let’s review them before coming up with a strategy to maintain sharp stars in your nocturnal landscape photographs.

Five Factors

Focal length

More than anything else, the focal length of your lens determines the longest usable shutter speed. In general, the wider your lens, the longer you can expose without showing stellar movement. Some people use a formula such as the 400 Rule or 500 Rule to calculate shutter speed. These formulas can be helpful, but do not take variables other than focal length into account.

Orientation

Camera orientation relative to the North Star is the next variable that needs to be factored into an exposure. Since it takes Earth 24 hours to make one complete rotation, a hypothetical 24-hour exposure with the camera oriented toward the north or south (depending on which hemisphere the photographer is shooting in) will record star trails that form a complete circle. Stars near the pole star will create small circles, while stars in the opposite part of the sky will create much larger circles in the same exposure.

Therefore, if a camera is directed due-north in the Northern Hemisphere, or due-south in the Southern Hemisphere, the resulting star trails created during a long exposure will be noticeably shorter than star trails in photographs where the camera is pointed away from the pole. This means that the longest usable shutter speed for “freezing” stars increases substantially as the camera’s orientation approaches north or south.

Pemaquid Point Lighthouse, Maine. This wide-angle view of the oft-photographed lighthouse shows relatively little stellar movement in the northern part of the sky on the left side of the frame, and much more to the east on the right side of the frame (see detail photos, below). Nikon D750, Zeiss 21mm f/2.8 lens. 30 seconds, f/4, ISO 6400.

Pemaquid Point Lighthouse, Maine. This wide-angle view of the oft-photographed lighthouse shows relatively little stellar movement in the northern part of the sky on the left side of the frame, and much more to the east on the right side of the frame (see detail photos, below). Nikon D750, Zeiss 21mm f/2.8 lens. 30 seconds, f/4, ISO 6400.

Pemaquid detail north

Pemaquid detail north

Pemaquid detail east

Pemaquid detail east

Sensor

Sensor size, or camera format, also make a difference. Movements during an exposure cover a larger percentage of a small sensor relative to a larger one. This is similar in principal to a telephoto lens giving the impression of longer star trails due to a narrower angle of view than a wide angle lens. It takes less time for a star to transverse a smaller sensor than a larger one, or to cross the image plane of a telephoto image than a wide-angle one. The star trails are actually the same size in each photograph, but appear larger due to their size relative to the frame. Therefore, the smaller the sensor, the shorter the longest usable shutter speed.

Resolution

Camera resolution also impacts apparent movement of stars, or anything else in an image. Higher-resolution sensors show more detail, and therefore amplify any flaws in an image as well as the image itself.

Final view

However, increased resolution’s impact on an image is tied to the last considerations in determining longest usable shutter speed: final image size, viewing medium and viewing distance.

If a photograph will be viewed as a small print, there is more tolerance for movement, because it won’t be noticeable to the viewer—and thus you can get away with a longer shutter speed than you could for a more highly magnified, larger print. The same is true if the image will be viewed only on a screen, as opposed to as a print.

Lastly, the more distant the image from the viewer, the less apparent any movement or other “flaws” will be. An extreme example of this is demonstrated by Apple’s use of iPhone photographs on giant billboards! A 12 megapixel file from an iPhone 7 must be magnified tremendously to achieve billboard scale, resulting a very low resolution image. But because billboards are viewed from a substantial distance, the images used can be extremely low resolution and still appear to be good quality. Typically, billboard images are printed at 40 to 50 dpi, as opposed to 300 dpi and higher for photographic prints.

This means that a low resolution image viewed from a great distance is very forgiving of subject, or for that matter, of camera movement. Conversely, a high resolution print that is meant to be viewed at close distance will reveal every possible detail (and flaw) contained in the photograph.

Putting It All Together

Despite the apparent complexity of this multitude of variables, a little experience is all that it takes to effectively determine the longest usable shutter speed for astro-landscape photographs. By keeping these variables in mind while photographing, making critical observations and appropriate adjustments, sharp star images are well within reach.

The Milky Way over Mono Lake. The moon is just about to rise under the arch of the Milky Way in the eastern sky. Some movement is visible at full magnification, but the best combination of exposure variables was used to achieve a balance between image noise, depth of field and star points. Compromise is almost always necessary to get the shot. Figuring out how to make those compromises is what makes for successful astro-landscape photographs. Canon 6D and Sigma 24mm f/1.4 lens. Panorama consisting of five vertical images, each 20 seconds, f/4, ISO 6400.

The Milky Way over Mono Lake. The moon is just about to rise under the arch of the Milky Way in the eastern sky. Some movement is visible at full magnification, but the best combination of exposure variables was used to achieve a balance between image noise, depth of field and star points. Compromise is almost always necessary to get the shot. Figuring out how to make those compromises is what makes for successful astro-landscape photographs. Canon 6D and Sigma 24mm f/1.4 lens. Panorama consisting of five vertical images, each 20 seconds, f/4, ISO 6400.

In the second part of this article, I’ll compare the use of the 400 and 500 Rules with different focal length lenses to help you further refine your technique.

Stay tuned for Part II of this article in a few weeks.

Lance Keimig has been photographing at night for 30 years, and is the author of Night Photography and Light Painting: Finding Your Way in the Dark (Focal Press, 2015). Learn more about his images and workshops at www.thenightskye.com.

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