Bokeh is essentially the blurry area of a photograph that has a shallow depth of field. When distinct lights are in that blurry area, they will form shapes, usually circles. The shape is determined by the camera and lens used, and the shape of the shutter as it opens. Without getting crazy scientific about it, basically, the light is forming the shape of whatever the shutter lets in. You can easily manipulate that shape or design by adding a filter on the front of the lens.
The most common way to make bokeh shapes is by cutting the shape into a piece of card stock that you fit over the front of your lens. I used to have a detailed tutorial on this, but it was lost on an old version of my photography website, but you can find plenty of them on Pinterest or via Google Search. A shaped hole punch works perfectly for this, or you can get crazy with a razor blade. You want the shape to be relatively small in the center of your “filter”. You can choose any creative way to attach it to you lens. Some people cut their filter into the exact shape of the lens, leaving tabs on the sides to bend and secure on the lens with a rubber band. I had my filters cut to size and then used light masking tape to hold them into place. Or you can just hold it.
But, the trick is that you need to focus on your subject before you add the filter. Don’t forget to choose a background with sharp lights. Now, with no filter, set your camera to Aperture Priority or Manual (if you know how to use Manual) and choose your largest aperture/smallest number. Here’s a detailed tutorial on aperture to help you. Use auto focus to focus on your subject. Then set the camera to manual focus so the focus won’t change. Add your filter to the front of your lens. Take the picture! If all goes well, your subject will be in focus, and your background lights will have taken the shape of your filter. The first image below of my husband was shot this way with this type of filter. He was standing on our condo balcony with the city lights of Waikiki in the background.
You don’t always have to focus on a subject first. You can just make designs with the blurred lights if you want. That’s what I did with the rest of the images below.
I also tried an easier way to create a bokeh filter. It’s kind of a cheat, but then again, it allows for more detailed designs. I simply took clear plastic (I used a sandwich bag) and used a black Sharpie marker to create my shape. Make sure you are leaving your shape clear and filling in the rest of the plastic (as much as will cover your lens) with black. This won’t necessarily give you as clean of a look, though, as you can see in some of the images below. The clear plastic texture make seem perfectly clear when you’re looking at it, but it shows up pretty well in the bokeh. This isn’t terrible for playing around with your Halloween shapes, but you might have trouble getting a clear picture of a subject with this method. Or you can find clearer plastic material to use. Also note, the skull shape was drawn directly with the black Sharpie, not outlined with the skull clear, as it should have been.
Here is a series of shots I did with Halloween faces. These are not lights in the shapes that you see. They are just city lights blurred in the background, with a shaped filter over the lens. Enjoy!