DIY Bokeh or “how to make pretty stars”

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:

star-bokeh-snowman

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.

heart-star-bokeh

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.

heart-bokeh

Other than that, it’s really not too hard and with a material cost approaching zero, why not give it a shot?

13 Comments

  1. Thank you so much for this information. All of the guidelines that did not seem to appear to be posted anywhere else really helped… in fact, without them I would be completely lost! Just got my 50mm today… so far, I love it!

    Reply

    1. Glad it was helpful. That 50 is a great lens. By great I mean extremely good value and really incomparable to anything else Canon makes. If you take some good shots, post a link!

      Reply

  2. hey, i am trying this but when i shoot, its the shape that shows only, no other objects or elements.. thanks, help 🙁

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  3. Heya this is kinda of off topic but I was wondering if blogs use WYSIWYG editors or if you have to manually code with HTML. I’m starting a blog soon but have no coding skills so I wanted to get advice from someone with experience. Any help would be greatly appreciated!

    Reply

  4. I’ve had a Nikon D70s for several years, and have only recently begun to really dig down into what all the settings are and mess around with the ones buried in the menus and I finally started to feel ‘at home’ with it.

    This concept/term ‘bokeh’ was entirely new to me until a few days ago, and it’s what I’ve been missing.

    The mention here in the comments about a 50mm purchase reminded me of why I *sold* my digital Nikkor 50mm f/1.4. It didn’t give me any of the satisfaction that my old Canon FTB + 50mm 1.4 lens did, and I now believe it was because the lens was too crisp and didn’t give any of that bokeh effect (or not where I knew how to find it).

    Very nice explanation of this technique, thank you.

    Reply

    1. Thanks for the thoughts Mari – each lens has it’s own ups and downs, both the obvious technical specs, plus the things that they happened to do to achieve those things (like the number and shape of the aperture blades). It’s not often something you’d consider up front, but it affects how you use the lens and how much you enjoy it for any specific use.

      Reply

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