For all that our cameras are capable of rendering the world in glorious Technicolor, their light meters are remarkably simple: they can only 'see' in shades of grey. When a light meter attempts to judge the correct exposure for a scene, it does so under the assumption that the scene's average brightness is middle grey (18% grey), which is exactly half-way between absolute black and bright white.
The twinkling lights and glittering decorations of our Christmas tree are always far too good a photographic opportunity to pass up. Last year they were my testing ground for a Pentax X-5 that I had to review. This year, I decided to play around with zoom bursting, to make it appear as if the lights are bursting out of the image. While the abstract motion effect of a zoom burst might look as if it's a pain to achieve, it actually isn't that hard. You definitely need a zoom lens on your camera and preferably a tripod; then you just need a bit of patience to get it right.
Compose your frame and focus on your subject. It's actually one occasion when centre-focusing really does work and doesn't leave your composition feeling flat and dull. But of course, it's whatever works for your photo. You'll probably find it easiest to zoom in as close as you can and then lock your focus or set it manually.
In order to achieve the motion effect you'll need a slow shutter speed, so that you have sufficient time to turn the zoom ring on your lens. If you're not confident using full manual control, do flick your camera into Shutter Priority (S or Tv) mode. For this series of photos I experimented with exposure times ranging from one-and-half seconds to ten seconds. The optimal speed seemed to be five seconds, but of course it is going to to vary depending on your subject.
I kept the aperture fairly small and the ISO relatively low. Being a long exposure shot, there was a strong possibility that it would come out over-exposed if I adhered precisely to the camera's meter, so I under-exposed by a stop-and-half. If I'd been shooting in Shutter Priority mode, I would have achieved the same effect by applying exposure compensation.
When you're ready, depress your shutter button, or use a remote release to help avoid camera shake, and then steadily zoom out throughout the course of the exposure. If you'd like to ensure a little more definition for your subject, don't begin to move the zoom ring immediately, but let it rest for about a quarter of the exposure time and then start to move it.
In most cases, you will probably want to zoom out to give the impression of the subject bursting forth from the image. I also played around with zooming in and rather liked the effect. It's all going to depend on what works for your photo.
Once you have the basics down, it'll be a case of playing around to see what looks best. Have fun!