A lot of effort goes into making cameras and lenses that take sharp pictures but there are times when I like to throw sharpness out the window and just have fun with color and lights. One of my favorite tricks is to set the camera with a slow shutter speed (use your shutter-priority exposure mode to select a long shutter speed) and then jiggle the camera during the exposure. The technique works particularly well with Christmas lights because they're very colorful and you get wild patterns depending on how you move the camera and how long you keep the shutter open.
The actual shutter speed you use will depend more on the effect you want than the actual exposure since you're really not after a perfect exposure, but rather a curious pattern of color and light. Typically though shutter speeds ranging from about 1/4 second to one or two full seconds work well and provide you with enough time to get a good jiggle going. I used an exposure of 1/3 second (in my Nikon camera it's displayed as .3 seconds) to take this abstract shot of a lighted Christmas ball (one of those 10" balls with multi-colored lights) and, because I was using the shutter-priority exposure mode, the camera selected the proper f/stop for me. I shot dozens of photos of the ball experimenting with different camera motions: side-to-side, big circles, little circles and also just randomly shaking the camera. All of the photos were fun to create and fun to look at.
Perhaps the best part of taking abstract photos like this is that there are no rules and you can have a lot of fun not worrying about getting sharp photos. You will have to turn off your anti-shake mode (if your camera has one) otherwise the camera is trying to compensate for the motion--one more case of technology getting in the way of creativity. Shoot lots of pictures once you find a good subject--you may come up with a great shot for next year's Christmas cards.
1 week ago