Hasta La Ideas

The POÄNG isn’t the focus of this story…

Boasting a killer combo of imaging innovation and NewDealDesign’s award-winning form factor, the Lytro camera is certainly at the top of the list for many tech geeks this year. We have yet to see if the rectilinear gadget will find a place in the serious photographer’s existing arsenal of DSLR, lenses and the like or if it is more of a mass-market plaything. (The $400 pricetag suggests that it’s somewhere in between, and it’s difficult to predict the long-term adoption and impact of images with infinite focal points.)

While there might be more to Lytro than meets eye, the folks at Chaos Collective have devised an SLR hack to approximate exactly what meets the eye in depth-of-field (DOF) changeable photos. Rather than capturing this information over space, as Lytro’s pricey micro-lens array does, they’ve repurposed good ol’-fashioned moving image recording to capture this information over time:

First, let’s briefly discuss how cameras like Lytro work. Instead of capturing a single image through a single lens, Lytro uses a micro-lens array to capture lots of images at the same time. A light field engine then makes sense of all the different rays of light entering the camera and can use that information to allow you to refocus the image after it’s been taken.

But since we only had a digital SLR hanging around the studio, we started looking at ways to achieve the same effect without needing micro-lens arrays and light field engines. The idea is simple; take lots of pictures back to back at various focal distances (collecting the same information, but over time). Then later, we can sweep through those images to pick out the exact focal distance we want to use.

But wait… A sequence of images is just a video! And since most digital SLRs these days make it super easy to capture video and manually adjust focus, that’s all you need. Just hold the camera very still (a tripod is nice, but not necessary), shoot some video, and adjust the focus from near to far. That’s it.

Since most cameras capture video at 30 fps, it doesn’t take a rocket scientist to figure out that a couple of seconds will yield 60+ ‘slices’ of focal distance. The real trick was to accurately map out the focal clarity of the image:

Of course, once we had the video, the next step was to figure out how to make a simple tool that could process each frame of video and compute the clarity of focus for various points in the frame. We ended up using a 20×20 grid, giving us 400 selectable regions to play with. Making the grid finer is simple, but we noticed that making it too small actually made it harder to calculate focal clarity. The reason: we’re looking at the difference between rough and smooth transitions in the image. If the grid is too small, smooth surfaces become difficult to accurately detect. Tighter grids also produce large embed code, so we stuck with 20×20 as grid that dense-enough without introducing extra overhead.

Here are the results:

NB: They note that the media is embedded with HTML5 video tag for cross-browser compatibilty, but as of press time the images weren’t working in Firefox…

A few more—and Chaos Collective’s “Make Your Own DOF-Changeable Image” tool—after the jump…

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