Snapshot: Shooting by MoonlightPhotographers are normally fixated on finding good light; but there's a whole world of possibilities that opens up when the light goes away. A few months ago, I...
Ben Long, Macworld.com
Photographers are normally fixated on finding good light; but there's a whole world of possibilities that opens up when the light goes away. A few months ago, I found myself in Monument Valley in the middle of the night. Without other light to compete with, the full moon turned into a powerful light source, creating dramatic, hard-edged shadows in the desert landscape.
With their extremely sensitive sensors, modern DSLRs are ideal for shooting at night. When you take a long exposure, your camera can gather up more light and color information than your eye can collect, so the camera sees far more detail. In fact, aside from some white-balance adjustment, I did very little processing to the image you see here--almost all of the work was done by the camera. However, night photography brings a whole new set of challenges.
Framing the shot
To find the scene I wanted to shoot, I looked for interesting plays of light and shadow. When I found what I wanted, I set up my camera and tripod and went to work trying to frame the shot.
I say "trying" because one of the trickiest things about shooting when it's very dark is that you can't see your subject very well--if at all--through the viewfinder. While the moonlight in Monument Valley was bright enough to cast shadows, I had to look through the viewfinder for a long time before my eyes adjusted, and even then I could see only vague forms. (Don't worry if you don't get it exactly right at first, you'll be able to adjust once you've taken a test shot.)
Another challenge was finding the right camera settings. To ensure a broad depth of field, I put the camera in aperture-priority mode. Ideally, I would have liked to use an aperture around f/11, but that would have required a shutter speed of over a minute--long enough that the stars would begin to leave light trails. While star trails are a nice effect, for this image, I wanted pinpoints of light. Longer exposure times can also result in more image noise; as exposure time lengthens, some pixels on the sensor can get stuck and appear in your final image as white dots. So I knew I needed to shorten the exposure time. I figured that at f/5.6 I could get the depth of field I needed while still keeping the shutter speed relatively fast.
Tip: If your camera can display a status display on the rear LCD, activate this feature. My 5D Mark II, for example, even lets me change settings using this screen. With the camera mounted on a tripod, and light levels low, this is usually the easiest way to see and adjust settings.
Focusing in the dark
The next issue was focusing the camera. In low light, your camera's auto-focus feature won't work; it's simply too blind. This means you'll have to focus manually--no easy task since you'll have an equally hard time seeing details.
For a landscape shot, it's tempting to simply turn the manual focus ring to infinity. But if you focus on infinity, a lot of depth of field will fall beyond the horizon. To ensure your foreground is in focus, you want as much depth of field as possible in front of the horizon. So, rather than focusing on infinity, I prefer to focus just a little short of infinity.
The focus ring on your lens will show an infinity symbol at one end. Note that on most lenses, as you approach infinity, a tiny turn of the lens ring can equate to a big change in focus. So you'll want to make very small moves when you pull back from the infinity mark. On the focus readout of some lenses--such as those from Canon and Sigma--infinity is denoted by an L-shaped mark. (As temperatures rise, the infinity point shifts slightly to the right. Most of the time, though, the vertical leg of the infinity mark will be your reference point.)
Taking a test shot
Having taken an initial stab at framing and focusing, I was finally ready to take a test shot. To get this done quickly, I set the camera's ISO very high to 6400. Yes, this produced an image that was noisier than I wanted; but for a reference shot, that didn't matter. I was able to use the resulting image on the LCD to evaluate my composition and focus (zooming in on an LCD screen isn't the ideal way to check focus, but it's the only option in these circumstances) and adjust accordingly. The faster ISO means that my shutter speeds are faster, so I can more quickly snap these throw-away test shots.
Tip: when shooting in the dark, I recommend shooting in raw mode, so that you can adjust the white balance later, in your image editor.
Taking the Shot
I was now ready for a final image. I turned my ISO back down to1600--low enough to provide a clean image without lengthening my exposure time so much that I lose sharpness in the stars--and then took the shot.
Tip To minimize vibration on long-exposure shots, you'll want to either use the self-timer or a remote control. If your SLR offers a mirror lock-up feature, you might want to activate that as well. When mirror lock-up is activated, the camera flips up the mirror but doesn't trip the shutter until you press the button a second time.
The pros and cons of long-exposure noise reduction
Some cameras have a noise reduction feature that's tailored specifically to long exposures. Although useful, this feature sometimes requires as much time to process the shot as it took to shoot it. So, if you shoot a minute-long exposure, the camera will then sit for another minute and process after the shot. (You can't use the camera while it's working.) Other cameras can perform the reduction in real-time, while the shot is being taken. Check out your camera ahead of time to find out how its noise-reduction feature works. If it will effectively double your exposure times, you may want to shut it off during very long exposures--or you'll spend a lot of time twiddling your thumbs.
[Macworld senior contributor Ben Long is the author of Complete Digital Photography, fourth edition (Charles River Media, 2007). More of Ben's work can be found at Complete Digital Photography.]
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