I tried hard to drink in every bit of the fast-paced live-action Scott Pilgrim movie, which was packed full of neat little details and sight gags. I completely missed this clever trick in the trailers, but as soon as I saw it in the theatre I got so excited I yelled loudly whispered “LOOK AT THE BOKEH!”.

During the bus-ride scene after the first fight, Ramona explains to Scott that he’ll have to defeat her seven evil exes. Look at the street lights moving past in the background!

What’s going on here?

When a lens focuses on something in the foreground, the background gets blurry. Photographers call this “depth of field” and it’s used all the time by portrait photographers make their subjects stand out. Film directors use it to help you know where to look. This blurryness has a name: “Bokeh” .

Usually you don’t notice bokeh in the background because it looks smooth and continuous, unless your light source is tiny and bright.  Bokeh around a point light usually looks circular or octagonal – think about any blurry pictures you’ve taken of Christmas lights. The circular shape isn’t natural – it’s caused by the shape of your lens aperture, the little hole behind your lens that helps your camera focus and control light.

I want to do the Scott Pilgrim Lens Effect!

There’s two ways to accomplish this effect – the easy analog way, or the (sneaky) even easier digital way.

The analog way is as simple as cutting a shaped hole into a piece of construction paper and taping it over your lens. It looks crazy, but it works! Basically the hole becomes an aperture, and its shape gets projected onto your sensor. Take a picture in “Portrait” mode, or crank your aperture way wide, and take a shot. Because you’re limiting the light coming into your sensor, and probably taking pictures at night, you’ll almost definitely need to use a flash on anything in the foreground that you don’t want blurred.

(This picture is from DIYPhotography.net)

Using this cute heart-shaped cutout, you can take pictures like RottieLover on Flickr, who grabbed this adorable snap of their critter friend.

The digital way requires some software that will do “Shape Blur”. Back in the day the trick was to make an enormous filter matrix and apply it to your image using custom software. The new versions of Photoshop have it built in (since CS2 I think) and now you’ll find it in After Effects, Digital Fusion, and a bunch of other packages.

Start with a 16-bit picture (8 will work too, but for mathematical reasons you’ll get better results with a raw image) with really sharp well-focused point sources of light (street-lamps, christmas lights, ferris wheel bulbs) and then run a “Filter->Shape Blur” on the part of the image that you want the custom bokeh effect to show up in. Depending on your initial image and the size of the shape you do, you might need to brighten the results for them to be obvious. (Blurring spreads out the light) If you have a foreground subject you’ll have to be selective (using a selection, or a mask) so you don’t blur your dog or your Scott Pilgrim.

Some Christmas lights on my living room floor

Shazam! Cute hearts!

Or better yet – XMAS SPACE INVASION! OH THE HUMANITY!

So how cool is it that the Scott Pilgrim photography unit (or, more likely the VFX post unit) are using bokeh as another tool for storytelling? I’ve never seen it done before in a film – only in hokey experimental photography. So clever! I expect to see this making it’s way into all kinds of subliminally dreamy movie sequences with little point lights. Be on the lookout!