Shoot now, focus later: Change the focus after you take a photo

The line separating reality and science fiction continues to blur. Whereas 40 years ago, cameras that focused themselves were unfathomable, auto-focus lenses have been a routine part of photography since the 1980s. Fast forward to today, and you can purchase the Lytro camera, which does away with the idea of focusing entirely: You can change the focus of Lytro photos after they’re taken. The coolest part? I’m going to tell you how to simulate Lytro photos with the camera you already own.

What is Lytro?

But first, some background. The Lytro is a game-changing camera. If you haven’t yet seen Lytro images in action, prepare to be amazed—the effect is truly stunning. You can click anywhere in a Lytro photo, and the place you clicked snaps into sharp focus. That means you don’t have to decide on your composition before you shoot the photo. Lytro calls this “light-field photography,” because the camera doesn’t focus all the light rays to a single point, like a traditional camera, but captures the entire light field, recording data about every ray entering the camera.

The Lytro takes photos whose focus can be adjusted with a click at any time.

For what it does, the Lytro is surprisingly affordable (the 8GB model costs $400), but it's more limited than a traditional DSLR: You can’t change its single 8X optical zoom lens, for example, and it only works with a narrow range of PCs (64-bit Windows 7 and Windows 8 and Mac OS X). There’s no flash. It doesn’t even look like a camera; it’s a featureless aluminum tube that's reminiscent of a futuristic kaleidoscope.

Want to experiment with the Lytro’s variable focusing abilities? Check out the interactive Lytro photo gallery.

Take light-field photos with your own camera

The Lytro is getting a ton of buzz and there’s no doubt that it’s fun to play with. But you don’t need to spend $400 on a Lytro. You can simulate light-field photography with your own digital camera.

To do this, all you need is a digital camera that can shoot video, and which has a manual focus control that you can use to change focus while the video is being recorded. For best results, put your camera on a tripod (or at least place it on a tabletop or some other surface where it won’t move) and focus on something nearby. Start recording video, and over the course of a few seconds, slowly dial the focus so objects far in the background come into focus. Then stop the recording. When you’re done, copy the video to your computer.

Choose a scene in which you can easily see the effect of changing focus, with objects near, mid, and far.

What makes this little trick possible is a cool Web app hacked together by The Chaos Collective. But before you can upload your video to the tool and play with it in a webpage, you’ll probably need to edit the video file a little. Any video editing program will do, and I've had good experiences with the cross-platform VideoPad Video Editor from NCH software.  It’s easy to use and free. Of course, Mac users may also prefer iMovie. Just load your video into VideoPad’s timeline and then choose File, Export. Choose Computer/Data and pick the .mp4 file format. Finally, resize the video so it’s small enough to work well on the Web—I suggest 854 by 480—YouTube HQ. Then create the new video.

When you’re done, go to the Chaos Collective’s Make Your Own DOF-Changeable Image page and choose the file you just created. After a few moments, you’ll see your video transformed into a still image that you can click to change the focus. It seems magical.

Afterwards, you can click the upload and share link to post your creation to Twitter, Facebook, and elsewhere so other people can click around in your photo as well.

This should work in any browser, but I have had the most success viewing these images in Chrome. Here is the variable-focus version of a photo I shot on the Santa Monica Promenade.

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