Everyone has seen pictures like this with points of light in the background. The technique where shallow depth of field allows you to throw everything but the subject out of focus is known as Bokeh. What I’ve always noticed is the way points of light look in the out of focus area. I also learned that you can shape them, and when I finally got around to it I made my own:
For more info on how it works and all the nerdly stuff, hit the jump.
The reason the lights look octagonal in the link above is because you’re seeing the blades of the aperture – the small hole in the lens that lets the light in. If you get a lens with a big enough aperture (like my favorite 50mm lens with a massive f/1.8), you can make your own smaller, shaped aperture and put it in front of it. From what I’ve read here and here, the equation is your lens focal length (so 50mm in my case), divided by your maximum aperture (1.8 in my case) gets you 27.7mm, which is the max size that the hole can be and still be effective. Now all you need to do is make a black paper cover for the front of your lens with the shape you’d like in your pictures in front. I’ve got hearts and stars.
With the cover fitted over your lens, you should be able to see the results right through the viewfinder, so your results shouldn’t be a surprise. There are a few other guidelines I haven’t seen posted elsewhere:
- This only works with points of light, not the sun or big lightbulbs, unless they’re far enough away. This means mostly shots at night, unless you have a suitably darkened room during the day.
- The shapes will only appear when the lens is thrown full out of focus, which means either you need a subject very close to the lens in the foreground and the lights in the background or you are going to have a picture with no in-focus subject.
- Creating a new aperture means that you’re cutting down on the light available for the camera. The camera will meter through your new aperture, so the pictures should be properly exposed, but you might want to compose without the lens hood on, then slip it on to take the picture.
- Make sure you’re in Aperture Priority mode (Av on most cameras) and that your aperture is set wide open (the lowest number you’ve got.
- You probably also want to focus the camera manually (or automatically and then flip it into manual mode) so that you keep the wildly out-of-focus background you’re going for.
- Since you’re taking pictures in a dark environment and the flash is out, you’re probably going to want to use a tripod, or at least set the camera down on something. You can make some cool patterns with the blur, but you lose most of the shape effect.
Other than that, it’s really not too hard and with a material cost approaching zero, why not give it a shot?
- Aperture: ƒ/1.8
- Camera: Canon EOS DIGITAL REBEL XT
- Focal length: 50mm
- ISO: 200
- Shutter speed: 6s