Tuesday, September 18, 2012
Shoot For The Stars
Good Night Sky • When The World Is Flat • Staking A Clamp Or Plamp
Good Night Sky
Q Lately I've seen a number of interesting images of the night sky showing a silhouetted foreground and the Milky Way. Does this take special equipment? How is it done?
A You can accomplish astro-landscape images that include the Milky Way; you'll need a dark night sky, a recent-generation digital camera and some standard techniques.
You need a recent DSLR camera because these have improved capabilities at high ISO settings. At higher ISOs, the newer cameras' sensors are extremely sensitive to light with less of the by-product of excessive grain or "noise," which is evidenced in random color and tonal anomalies. Film cameras functioned well at ISOs (film rated) of 100 or less. Early digital cameras worked well at ISO 100 to 400 and with short exposures. The latest DSLRs (in my own experience, the Canon EOS 5D Mark II and Mark III; other manufacturers market cameras with similar ISO capabilities) have excellent low-noise properties at ISO 1600 and 3200. They also give good results with exposures that range from 30 seconds to many minutes. It's because of these advancements that you're now seeing beautiful night sky images that weren't possible only a couple of years ago.
The preferred lens for the night sky is a wide-angle that's fast, as in a large ƒ-stop. The ideal lens is a 35mm ƒ/1.4, but wide-angles in the ƒ/2.8 to ƒ/4 range can be employed with not quite as spectacular results. Don't forget a tripod and cable release.
So now we're out of town, in the dark and have the right gear! Next, technique is critical. You're using a lens nearly wide-open, so focus must be dead-on due to the minimal depth of field. You accomplish this by using Live View on your camera's LCD. I find a bright star/planet, set the Live View magnification to 5x or 10x, and using a Hoodman Loupe (www.hoodmanusa.com), bring the fuzzy star/planet into a pinpoint of light. Then, determine the exposure. Your exposure needs to be no longer than 30 seconds. The earth's rotation will render the stars as streaks in exposures longer than 30 seconds. (This can also produce interesting star-trail photographs, but right now, we're going for a sharp capture of the Milky Way.) The ƒ-stop needs to be nearly wide-open. Usually lenses aren't their best at the widest aperture, so normally I try to stop down one stop (to ƒ/2.0) with an ƒ/1.4 lens. You don't have this luxury with an ƒ/2.8 or ƒ/4 lens because you need as much light-gathering capability as possible and the higher ƒ-stops (smaller apertures) won't allow enough light to capture the Milky Way in 30 seconds. Next comes the ISO. Start with 1600, and then try 3200. At the higher ISO, you'll capture more information, but beware of noise. Postprocessing your images in Adobe Photoshop or Lightroom will enhance the overall look of the Milky Way and gas clouds; the better you capture them, the better the final result.
It should go without saying that composition, as always, counts. A foreground or base to the image is essential to conveying the enormity of the sky and the smallness of the earth and we creatures on it.It should go without saying that composition, as always, counts. A foreground or base to the image is essential to conveying the enormity of the sky and the smallness of the earth and we creatures on it. Some photographers use tree silhouettes, sometimes painted with flashlights; my example here uses some mountains, but I can imagine a number of striking foregrounds that would convey an interesting message, if you could get it all to come together.
There are many variations on photographing the night-sky landscape. Try star trails, time-lapses or panoramas. Take one of many classes being offered from an experienced night-sky specialist. One that comes to mind is Canon Explorer of Light Jennifer Wu, who has an upcoming program in Death Valley offered through the Canon Digital Learning Center (www.learn.usa.canon.com). Don't forget your headlamp!
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