Ten Tips for Exciting Nighttime Photography

There is a growing interest in a new kind of nighttime photography.  Photographers have been taking photographs of the nighttime sky ever since film was invented.  These photographs were generally long exposures that show beautiful star trails.  But now they are taking clear, sharp images of the stars and planets literally stopped in their tracks.

Astronomers have always been taking photographs of the nighttime sky and their goal has always been to get sharp images of the stars.  To do that they rigged their powerful telescopes with very precise motor drives that slowly turned the telescopes at the same rate as the stars move overhead, effectively holding the stars motionless in the field of view.

But with the advent of digital cameras the notion of photographing the night sky as part of a broader landscape has become increasingly popular.  And it’s not just star trail images that photographers are capturing.  They are capturing spectacular images of the planets, constellations and even the Milky Way over well known features on earth.  Wally Pacholka is one of the best of this new breed of photographers and his work is an outstanding example of this genre of fine art photography.  Check out Wally’s incredible Top Ten Night Sky Images to see what I’m talking about.

Nighttime photography like Wally’s can be both fun and rewarding.  But there are a couple of tricks you need to know in order to making it work.  Let’s take a look at them one by one.

Clear Sky

You need a night preferably without clouds.  The subject is the sky and you don’t want to obscure it.  Also, ideal conditions would be air that is dry.  Humidity in the atmosphere can cause flare around heavenly objects.  Dry air is best achieved on cold nights so you’ll need to wear very warm clothing and possibly use pocket warmers to keep your fingers and toes warm.

Dark Sky

For this kind of nighttime photography to be at its best the night sky must be at its darkest.  To get the most stars a good rule of thumb is to start photographing no sooner than three hours after sunset and stop no later than three hours before sunrise.  This guarantees that the sun is far enough below the horizon that its rays do not illuminate the upper reaches of our atmosphere.  Any light falling on the upper atmosphere will block out the very faint stars.  Wally does most of his best work at 2:00 AM.  But you can get very good results and still be asleep in your sleeping bag when Wally is out there creating his magic.

Another thing that can interfere with this kind of photography is the moon.  The ideal time to photograph is when there is a new moon.  At other times of the lunar cycle you want to make sure the moon is well below the horizon, same as the sun.  Even light from a partial moon on the upper atmosphere can overpower the dim stars.

A third thing that can interfere with nighttime photography is city lights.  It doesn’t take much of a city either to cast a glow on the horizon.  To give you an idea of how city lights can interfere with a clear view of the heavens, Death Valley has a light pollution problem because of the lights in Las Vegas 150 miles away.  So the ideal location is far away from the polluting effects of city lights.

Know Your Sky

Wally is as much of an astronomer as he is a fine art photographer.  He times his visits to the locations he shoots to coincide with celestial events.  But he does this photography for a living.  Personally, I just like to get out there when I’m on a photographic expedition and take what comes my way.  But knowing when well known constellations like Orion will be in your field of view can help you get even better images.  The time of the year and the time of night will determine what you will see, at least as far as the constellations are concerned.

The planets are a different story and move about the nighttime sky on their own erratic paths.  That’s why the origin for the word ‘planet’ is ‘wanderer.’

Comets and meteor showers are other occasions to photograph the night sky.  Knowing when a comet is in the vicinity of earth can product some unique images.  Meteor showers are a bit more challenging but with patience you can quite possibly catch one or two during a particularly active event.

Stop the Stars

You’d be surprised at how quickly the stars move across the sky.  A 30 second exposure can show detectible star trails given the right circumstances.  When determining a shutter speed that will ‘stop’ the stars you need to take into account the focal length of your lens.  If you look at stars through a powerful telescope you can actually see them move (if the telescope is not equipped with the kind of motor drive described above).  If the telescope is powerful enough even a 1 second exposure would produce a star trail.  But if we look at the heavens with our naked eyes we don’t detect any movement.

The lesson here is that the focal length of your lens will determine the maximum exposure time you can get away with and still ‘stop’ the stars.  Fortunately, there’s a simple calculation that you can almost perform in your head.

Exposure in seconds = 600 / {apparent focal length}

So, if your apparent focal length is 20 mm you can take a 30 second exposure (600 / 20).  If your focal length is 35 mm your exposure time drops to 17 seconds.  At 50 mm the longest exposure you will want to use is 12 seconds and at 100 mm it drops even further to 6 seconds.

Clearly you want to use a wide angle lens for this kind of work.  But the night sky is a pretty big thing to photograph so a wide angle lens is a natural choice.

Oh, one more thing.  If you’re not shooting with a full frame sensor, be sure to use the apparent focal length when performing the above calculation.  For example, if you have a 24 mm lens on a camera equipped with an APS-C size sensor, the apparent focal length is more like 38 mm (24 * 1.6).

Capture More Light

It’s really dark out there.  So, in addition to longer exposures you’ll want to shoot with a wide open aperture.  This is where fast lenses really earn their keep.  You’ll be glad you spent that extra couple of hundred dollars for the 2.8 or the 1.4 lens.  The more light your lens can capture the better.

Sensitivity is a Good Thing

You’ll also need to crank up your camera’s ISO.  In fact you may need to push it up pretty high.  When doing this kind of photography I frequently push the ISO to 1600.

The challenge with high ISO is noise.  The good news is the current crop of cameras have remarkably low noise at high ISO settings.  Full frame sensors have lower noise levels because of the greater light gathering capacity of their larger pixels.  APS-C sized sensors of necessity have smaller pixels which translates to higher noise levels at higher ISO settings.  Digicams have high densities of pixels crammed into very small sensors resulting in noise levels that probably render them useless for this kind of photography.

Seeing Clearly in the Dark

One challenge of night time photography is getting the image in focus.  Think of trying to get a sharp focus with a wide angle lens on a shadowy tree or tiny points of light in the sky on a cold, dark night.  The camera’s autofocus setting simply isn’t going to cut it.  So you need to focus manually.

What I like to do is take the camera off the tripod, zoom in on the brightest star in the sky and manually focus on it.  Then I can put the camera back on the tripod, zoom back out to the wide angle focal length I want and compose the image.

As added insurance it’s always wise to check the sharpness of your image after you’ve taken a test shot.  Your camera’s LCD screen is perfect for this.  Display the image and zoom in on a bright star to make sure it’s not fuzzy.  If it is, repeat the focusing procedure and try again.

Live view which is often very helpful in getting a tack sharp focus during daylight is useless in this situation.  All you get is a blank LCD screen.

Depth of Field

There’s one other relatively minor consideration and that is depth of field.  You’re shooting wide open and focusing at infinity.  We’re definitely not talking hyper-focus here.  The depth of field tends to be somewhat limited in this situation.  But the good news is we’re using a wide angle lens that has an inherently greater depth of field than a telephoto or even a normal lens.  So it’s probably not a serious concern.  You just need to realize that you won’t be able to do those dramatic near-far compositions where the foreground is inches from the front element of your lens.

Composition

Speaking of composition, working in the dark makes that just a little bit more difficult.  You’re not going to see much looking through your viewfinder and, like I said just a moment ago, Live View is useless.  You might try using a flashlight to illuminate the foreground objects while you peer through your viewfinder.  But that won’t help you with the stars.  So you’ll definitely want to take some test shots to check the composition on your LCD and make adjustments.  Also, if you include more of the scene than you think you’ll actually need for the final print you can do the fine cropping in the post processing.

Zap Your Camera

If you get hooked on nighttime photography you may want to take the ultimate step and have your camera modified.  Digital camera sensors are complex and delicate instruments.  Part of the complexity is a low pass filter that covers the actual sensor itself.  This filter effectively filters out all of the infrared light, allowing just the visible light to pass through.  But the night sky is awash in infrared light.  We can’t see it but our camera could if it didn’t have that low pass filter.  You can find companies on the Internet that will modify your camera for nighttime photography.  But it’s a one-way ticket.  Once done, it can’t be undone.

The other consideration is sensor cleaning.  When a D-SLR sensor is cleaned, it’s really the low pass filter that is cleaned.  When this filter is removed it’s the sensor itself that needs to be cleaned.  I certainly wouldn’t want to attempt that myself.

Enjoy

This is a really exciting form of photography.  Once you try it you may well find yourself heading out into the dark to not only gaze in wonder and awe at the night sky but also to capture it.

Good shooting.

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