On our recent live zoom, we talked about some thoroughly absorbing indoor projects that are great things to try if you want to escape the seasonal routine of food and telly for an hour or two, writes Jon Adams. One project that raised a few eyebrows and sparked a few questions was the ‘shaped bokeh idea’, and this is THE ideal technique to try over Christmas, as it works perfectly with fairy lights!
Inside every lens is a diaphragm ring which opens or closes as you adjust the aperture value. Its chief function is to let more or less light through to the sensor to give you a well-exposed picture, but the by-product of this is the way it affects the zone of sharp focus in the image. If the aperture is closed down to its smallest setting (f/22 on many lenses, but it can be a higher number), a very deep zone of sharpness is produced, and if it’s wide open (the smallest f/number), a very shallow depth-of-field is the result.
The quality of the out-of-focus areas is referred to as ‘bokeh’ (a Japanese word that roughly translates as fuzziness), and on pinpoints of light, this will reveal the shape of the ‘hole’ in the diaphragm ring. It’s normally as close to a circle as possible – but it doesn’t have to be! If you open your aperture to the smallest f/number available, you can cut a hole in a piece of black card, and once this hole is placed over the lens, you can render pinpoints of light in any bokeh shape you like. I wanted to convey my love of coffee with a simple heart shape, but the options are only limited by what you can cut out with scissors or a scalpel.
How to create custom bokeh shapes
1 Cut out your shape on a piece of card
Grab some black card, and then – if you want to be really precise – trace around the outside of the lens you’re using, and cut inside the line to produce a circle that holds itself snugly in place within the filter thread. If you want to be quick – just cut a square of card big enough to cover the front of the lens. Cut out your preferred shape in the middle – fold it in half first if you’re after a symmetrical shape.
2 Cover the lens with the card
You need a fast optic with a large, maximum aperture to get the best results, but the effect will work with any lens. We used a 50mm f/1.4 prime lens, and set the aperture to its maximum setting of f/1.4. You can attach the card to the edge of the lens with Blu-Tack, or, with your camera on a tripod, you can simply hold it over the lens while checking the effect using Live View.
3 Compose & shoot
Drape some string lights over a dark background to give your pinpoints of light, and then focus on a subject close to the lens. Provided the background and lights are sufficiently out of focus, you’ll see the shaped bokeh appear (in Live View). Use Aperture Priority mode, set your ISO to its lowest value and dial in your maximum aperture (the lowest f/number), and the shutter speed will take care of itself.
Try a few variations…
To vary the bokeh effect, try moving the subject closer to (or further from) the camera, so the background lights are thrown more (or less) out of focus. Don’t stick with one shape, either. While you’re set up, it’s relatively quick to cut out another bokeh shape, so try a variety of ideas like stars, triangles or squares to mix it up. Just don’t go for circles, as a circular bokeh shape is the same as a wide-open aperture, and won’t make any difference!
Neat idea, thanks Jon!