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Apple iPhone 7 Plus’s new dual camera: Computational imaging finally goes mainstream

The massive expansion of available computing power, and declining cost of small imaging sensors, has spurred a wave of startups hoping to combine those trends in products that feature computational imaging. The basic premise is to automatically post-process images from multiple sensors to create an improved image that would have been difficult to capture otherwise.

For example, Lytro famously used computational imaging to allow refocusing of an image after the fact. Pelican’s array camera created depth maps, allowing depth of focus to be set after the image was shot. Light.co has announced a smartphone-sized camera that combines the output of 16 fixed-focal-length cameras to simulate various effects including zoom. So far, though, none of those startups has achieved mass market success. As a result, computational imaging hasn’t received any real validation – until now.

Apple iPhone 7 Plus features a 2x optical zoom thanks to a second sensor and lensApple has announced that the iPhone 7 Plus will have a dual lens (and by inference, dual sensor) rear camera. One will be a state-of-the-art 12MP smartphone imager, essentially an improved version of the one in its current phones (it features a faster f/1.8 lens, optical image stabilization, and 60% faster readout). The second lens has a much longer focal length (56mm in full-frame equivalent terms). This design echoes Light.co’s choice of 2x focal length lenses on its upcoming L16.

The second sensor and lens allow Apple to do a number of things. First, and most obvious, it means you can zoom in on an image optically – by pressing the 2x button on the phone. That is a huge step forward for anyone tired of being confined to a typical smartphone wide-angle (28mm in the case of the iPhone 7 family, for example) field of view.

Beyond that, though, Apple is using the additional data to do some fancy post processing. Because the cameras are separate from each other, they will see slightly different versions of the image. That means that for objects within the field of view of the 56mm lens, the iPhone 7 Plus can infer a map of the depth of the objects in the frame. In particular, it can try to pick out the subject of the image (face detection helps with this also, of course).

Apple hasn’t said exactly how the technique will work, but one result will be a new Portrait mode that keeps the subject sharp while blurring the background. Another will be an additional Depth mode — shipping later this year — that simulates the shallow depth of focus and pleasing background “bokeh” that photographers have typically needed much larger and more expensive cameras to achieve.

The dual lens isn’t the only update to the camera on the iPhone 7 Plus. It (and the iPhone 7) also feature a four-LED, dual-tone flash for improved power output and better color balance. The front-facing camera has been upgraded from 5MP to 7MP. The new phones will also be able to capture 4K video, as well as slow motion in 1080p and 720p. For the first time, RAW image capture (in DNG format) will also be supported.

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