Almost a year ago, I took a class on night photography. I finally dusted off my tripod on our recent trip to San Luis Obispo and took some pictures of star trails. I've wanted to try it for a while, but it doesn't work in San Francisco, since you can't really see the stars due to the light the city generates at night.
San Luis Obispo doesn't have that problem. Each night was crystal clear with stars everywhere. I started taking shots with the shutter open for about 5 minutes, then pushed it to 15 minutes, then at the end, I was leaving the shutter open for 30 minutes straight.
The effect is pretty amazing - since the earth spins on its axis, keeping the shutter open that long creates star trails. I'm a newbie with star trails, but I learned a lot. Here are a few tips beyond what I listed in my previous blog post:
- Start with a fully charged battery! Digital cameras suck a lot of juice when leaving the shutter open for long shots.
- Turn off the display on the camera during long shots; the screen is one of the reasons your battery will drain.
- The shots look better if you get a little bit of the ground (or mountains) in the shot. Focus on the foreground, not the stars.
- If you want to take a shot of the sky only (no foreground objects), it will be impossible to focus on anything. Just set your lens to manual focus and set it to infinity focus.
- Turn OFF long exposure noise reduction setting if your camera has it - this will save a lot of battery juice. The process of noise reduction doubles the time your camera is working on a single shot. I can't remember all of the details, but I think the camera takes a black photo of the same exposure length, then compares that to your real shot to determine where there is noise. I had it on and a 15 minute shot took an extra 15 minutes of processing after the shot was complete (over half an hour before I could use my camera for the next shot).
One interesting point - the curvature of the star trails depends on where you point your camera in the sky. In some of my photos, you'll see the stars are curving down, looking kind of like a meteor shower. But in one or two shots, you'll see the stars curving up in a circular pattern. Some photographers can compose shots where the pattern is a full circle. If you want to get your geek on, read this article.
Some people create this effect by merging a series of many shots in photoshop (e.g., merging fifty 30-second shots). Given my lack of photoshop skills, my shots are au naturel. Round 3 will have to wait until our next trip somewhere quiet :-)