Tuesday, June 28, 2011

Catching lightning

7s, f/11, ISO 100, 17mm, fluorescent
It's severe storm season, kids.  You all know what that means:  time to go outside and watch lightning.  IMHO, lightning is the coolest display of God's awesome power.  I love taking pictures of lightning, even though I don't get as many opportunities to do so as I'd like.  Here's a few things I've learned about how to do it over the years.

First, be safe.  Don't stand there next to your tripod in the middle of an open field during an electrical storm.  You don't want to be the tallest thing around.  Nor do you want to stand really close to the tallest thing around (like a tree or a lamppost), because the electrical charge can radiate through the ground out from the base of that lightning rod for many feet.  The perfect spot from which to shoot is many miles away from the storm, where you're safe and dry.  If the storm is closer, go inside and shoot through a window.  An openable window is best, but a clean, dry sheet of glass (no screen) will do in a pinch.

Now that you're guaranteed to return home safely so you can view these great photos, let's start shooting.

10s, f/8, ISO 100, 200mm, tungsten
Photographing lightning is not unlike photographing fireworks, with one important difference:  you can tell (shortly) in advance when a firework will go off.  You have no such luxury with lightning.  There's lots of luck involved in shooting lightning, but as we all know, luck favors the prepared.  Before the storm hits, find a couple good vantage points for photographing lightning regardless of which direction the storm is.  Because you'll probably be shooting at after dark, pay attention to street lights, billboards, and other bright lights that may not be obvious during the day, but which would interfere with a night shot.  Storms can move pretty fast, so you probably won't have time to wander around looking for a good location after the lightning appears.

There isn't a great deal of equipment required for photographing lightning.  You really just need a camera (duh), lens, tripod, and cable release or remote trigger.

Just about any tripod will do, although the windier it is, the sturdier and heavier your tripod should be in order to keep your camera stationary throughout the entire exposure.  Don't try to rest your camera on a car window or stand your tripod on your hood if there's much wind, or if there are other people inside the car.  Your vehicle's suspension is soft enough that even a slight wind or interior movement will wobble the car around, rendering a great shot unusably blurry.  If you're the only one in the car on a calm night, you can probably get away with it.  You can get camera mounts that clamp onto the edge of a partially open car window, providing a very portable mount for these situations.

11s, f/8, ISO 100, 100mm, tungsten
As with most types of photography, there is no single best focal length for capturing lightning; it all depends on how far away and how localized the storm is.  I've used lenses from 10mm to 100mm with good results.  Just try to frame the area where bolts are most likely to appear, and shoot at the highest resolution possible so that you can crop down later if desired.  If there is any rain or any bright lights off to the side of the frame, you'll want a lens hood to help shield the surface of your lens.  One thing you do not need is a UV filter.  Bright lights in the frame can reflect off the front lens element and back off your filter, producing a double image of the lightning or any terrestrial lights that may occur in the frame.  No good can come from using a UV filter.  If you feel the need to protect your lens, use a hood, not a filter.

I don't care how fast you think your trigger finger is -- you can't reliably wait for a bolt to appear before you hit the shutter button.  The best method is to simply take one long exposure after another in hopes that you'll catch one or more bolts in your frame.  A really active storm can provide multiple bolts in a single frame for a really stunning composition.  In a slow storm, you'll end up with lots of throw away shots of a dark sky, but that's the price of admission.  For a dark, night sky, I usually use between 7-15 seconds with good results, though this can leave fast-moving clouds rather blurry, so you might need to shorten the exposure in high winds.  More later on exposure settings.

7s, f/5.6, ISO 400, 21mm, tungsten
I have heard of "lightning triggers" which will open your shutter as soon as a bolt occurs.  For a couple hundred bucks, these work similarly to optical flash triggers, and are plenty fast enough to catch most of a lightning bolt during daytime storms when you can't leave your shutter open for multiple seconds.  I've never used these myself, though, as we don't get many daytime electrical storms around here.  They'd probably also be useful for capturing nighttime bolts in windy conditions when you wanted to freeze the clouds with a faster exposure.

Because you generally want the background of your lightning photos to be quite dark, you shouldn't rely on the camera's automatic exposure settings.  Instead, do everything in manual mode.  Setting the correct exposure for lightning is not unlike exposing for flash photography.  To your camera, there are three components that affect the amount of light your camera records:  ISO, aperture, and shutter speed.  Because a lightning burst is so brief, the shutter speed doesn't have any affect on how brightly the bolt is recorded.  Consequently, you need only to set your ISO and aperture to a good value for imprinting the lightning.  For typical bolts, I find that ISO 100 + f/8, or ISO 200 + f/11, make a good combination.  Darker settings will make fainter bolts really blend in with the background, which isn't what you want.  With the ISO and aperture set properly for the lightning bolts, you can adjust the shutter speed to get a good exposure with minimal motion blur on any surrounding terrain, including clouds.

10s, f/5.6, ISO 200, 17mm, fluorescent
Try to keep the ISO as low as possible to reduce the noise in these long exposure shots.  Also try to keep the aperture at a medium setting.  Wider lenses will have plenty of depth of field even at f/8.  Longer lenses could benefit from f/11, especially if you've got foreground objects that want to stay in focus.  Dialing down to f/16 will get you plenty of DoF and nice, long exposures during which to catch numerous bolts, but each bolt will be rather faint and will lack the punch that you want from such a powerful event.

Speaking of focus, autofocus can be hard, and your camera certainly can't focus on a lightning bolt quickly enough to make the shot.  You need to pre-focus on something else ahead of time -- like a distant building or the horizon -- and then set the lens to manual focus (MF) so that it won't try to refocus on an empty sky before every shot.  Don't just blindly turn your lens' focus ring to infinity, as most lenses actually allow you to turn the ring past infinity, resulting in a blurry shot.

16s, f/8, ISO 100, 135mm, fluorescent
One area that frequently frustrates new lightning (and firework) shooters is white balance.  I can pretty much guarantee you that your camera's automatic white balance setting will suck for these shots, typically giving you a dirty orange sky.  Always set your white balance manually.  If you have something in the foreground that's bright enough to identify, you should set the white balance appropriately for that.  If all you have is a dark horizon line or clouds, then I usually set the white balance to tungsten (incandescent), which gives the sky a rich, blue color, or to fluorescent, which gives the sky a slightly purple tint.  Both look great for lightning or fireworks.  Nevertheless, you should always shoot lightning in RAW mode so that you've got the flexibility to monkey with the white balance setting later in post.

The final thing I want to discuss is composition.  Sure, lightning by itself in an empty sky can be impressive, but without some sense of scale, it's impossible for the viewer to really understand how big the bolt was.  Consequently, I always try to include some frame of reference in my lightning shots.  It may be the horizon line with a few trees or a cityscape.  If the cloud-to-cloud lightning is mostly overhead, sometimes the only other features I'm able to include are some cloud formations.  Take a couple no-lightning test shots of the surrounding terrain to make sure your shutter speed is set right to make the terrain look good.

13s, f/8, ISO 100, 70mm, tungsten
So how does this all come together when I go out to shoot?  I grab my Canon 7D, an appropriate lens (perhaps my Canon 10-22mm, or my Sigma 17-70mm, or even my Canon 70-70mm), my Manfrotto 055XProB tripod, and my no-name cable release / interval timer.  I setup the rig near a building where know I'll be safe and reasonably dry (the 7D is weather sealed, but the lenses are not, and rain on the front glass will ruin a shot).  I frame the shot to include an active area of sky as well as some sort of foreground feature or horizon.  I set the exposure to ISO 100, f/8, and leave the shutter speed on "bulb" so that it'll stay open as long as I hold down the button on my remote.  I take a couple test shots in the 7-15 second range to get my exposure nailed down for the clouds and terrain.  Once everything is set right, I could just set the interval timer to record an endless stream of frames until I stop it, but I prefer to tweak my settings and experiment every few shots.  Instead, I hold the button down myself and count what feels like a good exposure.  Every few shots, I glance quickly at the LCD preview to see what I need to change.  I try to have the shutter open as much as possible, because I never know when that killer bolt will appear, and I want to be ready.  (Cue Kenny Rogers singing about counting money at the table.)

I throw away lots of empty or lackluster shots, but you just have to expect that.  The title photo at the top of this post was the only shot out of 137 that night that caught any lightning at all.  Every other bolt was either out of frame or between frames.  I'm glad I didn't get discouraged and quit early.

Got any tips of your own to share?  Speak up in the comment section below!

1 comment:

  1. Thanks Ben for this detailed article. Looking forward to our next storm to try your technique.


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