Computational Photography and the Pixel

Of all of the features of Google’s new Pixel phones, the camera is receiving perhaps the loudest praise. It’s no wonder: most of the images I’ve seen look fantastic, especially in low light.

Sam Byford of the Verge spoke with Google’s Marc Levoy about how they used software to eke out the best photos they could from a fairly standard smartphone camera sensor:

The traditional way to produce an HDR image is to bracket: you take the same image multiple times while exposing different parts of the scene, which lets you merge the shots together to create a final photograph where nothing is too blown-out or noisy. Google’s method is very different — HDR+ also takes multiple images at once, but they’re all underexposed. This preserves highlights, but what about the noise in the shadows? Just leave it to math.


Google also claims that, counterintuitively, underexposing each HDR shot actually frees the camera up to produce better low-light results. “Because we can denoise very well by taking multiple images and aligning them, we can afford to keep the colors saturated in low light,” says Levoy. “Most other manufacturers don’t trust their colors in low light, and so they desaturate, and you’ll see that very clearly on a lot of phones — the colors will be muted in low light, and our colors will not be as muted.” But the aim isn’t to get rid of noise entirely at the expense of detail; Levoy says “we like preserving texture, and we’re willing to accept a little bit of noise in order to preserve texture.”

This sounds like a very clever workaround for getting great images from a sensor smaller than a postage stamp, and the results so far seem to support that.

However, some reviewers seem to prefer the warmer tones of the iPhone’s camera, and the Pixel doesn’t have the wide colour capture of the iPhone. While the former benefit is preferential, the latter benefit is becoming increasingly noticeable: the iPads Pro, the iMac, the iPhone 7, and — likely — next week’s MacBook Pros all support a wider colour gamut.

Of course, there’s a followup question worth asking: which of those is more important for a smartphone?