Beyond Focus (Part 2)

So let’s talk some more about the ramifications of the lightfield/plenoptic technology that I looked at in my last post.  For Lytro, the marketing push (and the accompanying press) are all about the ability to re-focus the image after the photo’s been taken, as a post-process.   And they show you these massive foreground-to-background refocuses.  But that’s really just a parlor trick – how often are you suddenly going to decide that the photo you shot would be much better off if the background were in focus instead of the person standing in the foreground?

On the other hand, being able to do a very subtle refocus – for example to make sure that the eyes in a close-up portrait are perfectly sharp – that has real value to almost all photographers and there’s many a shot I’ve taken where I wish I could do exactly that!

But there’s actually a lot more to this technology than just refocusing. In reality what you’ve got here (or more specifically what can be computed here) is an additional piece of data for every pixel in an image – information about the depth or distance-from-camera.

So it’s not just the ability to refocus on a certain object in the image, it’s an overall control over the focus of every depth plane.  The narrow-focus ‘Tilt-Shift’ effect becomes easy.  You can even have multiple planes of focus.  And macro photography is almost certainly going to see a big benefit as well.

While we’re at it, you’ll also have the ability to choose the exact characteristics of the out-of-focus areas – the bokeh.  This would include the ability to create ‘stunt bokeh’ similar to what certain lensbaby  products can produce (see here).

Oh, and it’s also pretty easy to generate a stereo image pair, if you’re into that sort of thing…

But wait, there’s more!  Making use of depth information is something we do all the time in the visual effects world.  Consider the image below.

Here’s the depth image for that scene, where brighter areas are (obviously) closer to camera.

In the same way that we can use this information to choose where to focus, we can apply other image adjustments to different depth areas.  Want to introduce some atmosphere?  Just color-correct the ‘distant’ pixels to be lower contrast.

From there it’s just a step away to compositing new elements into the scene – anything from a snowstorm to ravenous rampaging raptor robots.

Bottom line?  Computational photography in its many forms is the future of photography.  We’re almost certainly going to see the single-lens, single-sensor paradigm go away and we’re absolutely going to live in a world where more and more of the image-creation process occurs long after you’ve actually ‘taken’ the photograph.   Personally, I’m looking forward to it!

2 thoughts on “Beyond Focus (Part 2)

  1. One promising advantage of the Lytro (say over the Foveon) is that it uses existing sensors, and is ‘just’ adding microlens array and processing. The microlens array looks like it will be cheaper than the big glass. Can it even just be a screen, a micro pinhole-camera array?

    The car image above is interesting, and implies that the pixel at (x,y) can also have a z value pulled out of it. That should make Photosynth montages and 3D reconstruction easier. Maybe we’ll see the Man Who Fell to Earth’s camera soon.

    I agree that re-focusing after the fact will be more useful for small corrections than major back-to-front focus sweeps. But couple the image on a large display, with eye-tracking that focuses where you look, and that could be a new immersive experience. Let’s see you do *that* with your gelatin silver…

    On the processing side, the additional info captured in the light field should allow for correcting more lens defects, and give better images with cheaper glass (or even plastic). Like the ‘sensor dust’ image function in SLRs to capture a baseline ‘clean’ image, computational cameras will use calibration images to account for non-ideal optical components to produce the truest images.

    “Look at that fast software he’s driving. Must be compensating for small lens size.”

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