Not breaking new ground here. Plenty of other Bokehlishous Instructables...most notably:
Anywho, for those of you who have not experimented with the technique, here is my effort for the simplest and quickest way to get into the scene. No painstaking efforts (or talent) with an exacto knife and no permanent modifications. You should be up and running in 30 minutes.
The purpose of this Instructable is to construct a simple, quick and inexpensive "shaped bokeh" device for your digital or film camera.
Step 1: Stuff You Will Need
1. Specially shaped paper punches. Available at most hobby stores in a variety of shapes.
2. Black matte poster board. Again, commonly available.
4. Razor knife.
5. Black tape.
6. Camera...digital or film.
7. Lens for camera in Number 6.
8. A nice Christmas tree with multicolor lights (optional)
Step 2: Punch You Apertures
If you are having problems punching through the poster board, you can hit it gently with a rubber mallet.
Step 3: Construct Your Cone
1. Take a strip of poster board and make a tube to fit over you lens. Once you fit it, tape the tube so it holds its shape.
2. Trace a circle inside the tube and cut that out of poster board.
3. Cut a rectangle out of the center of the circle.
4. Cut a "U" shaped piece of poster board to act as a channel for your apertures.
5. Tape the "U" shaped piece to the circle.
6. Tape the circle to the tube you made in step 1.
7. Cut and fit the apertures to the width of the channel. Use them interchangeably
Step 4: Operations
1. The aperture decreases the light travelling through the lens, so long exposures are the norm. Invest in a tripod if you want the most stable picture. Try without for more "artistic" effects.
2. If you want to put things in the foreground, the easiest way is to put the camera on the "night mode." This mode lets you expose the foreground with the flash, but lags the shutter, so you can get your lovely bokeh exposed correctly as well.
3. Pick a lens/sensor size combination that will give you a shallow depth of field. Remember the background must be out of focus. A fast (low f-stop number) 50mm lens works well.
4. Turn autofocus off! Most autofocus systems look for high contrast and nothing will be higher than the pin point lights you are trying to get out of focus.
5. This technique only works with pinpoint lights. The best time to capture is at the winter holiday season when lights are everywhere. However, don't limit yourself...the big city at night can be a great source of point light sources.
6. Mess with your camera settings. Long exposure, short exposure, double exposure, flash, filters. Figure out what you like and work to make it better, just like any other photographic technique.
Have fun with your cheap, quick and effective bokeh machine.