How Nokia’s Amazing 41-Megapixel Phone Works

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The 808's sensor is the big one at bottom-right, next to typical phone and compact camera sensors. Photo Nokia
The 808's sensor is the big one at bottom-right, next to typical phone and compact camera sensors. Photo Nokia

BARCELONA, MOBILE WORLD CONGRESS 2012 — Yesterday, Nokia announced its crazy new 41 megapixel camera phone, the PureView 808, and the world chuckled. Just how big is the damn phone, I wondered, when Cult of Mac Deputy Editor John Brownlee woke me up and told me the news. But last night I spoke to a Nokia engineer, and it turns out this camera is pretty smart after all.

First, while the sensor does indeed contain 41 megapixels, it doesn’t snap 41MP photos. Instead, the sea of noisy data collected from those pixels is combined in software to get 5MP photos. Why? It started with the desire to design a better zoom.

Zoom lenses in cameras are problematic. They’re big, they’re intricate and — worst of all — they let in less light as you zoom. Even the fastest and most expensive DSLR zooms typically only manage a maximum aperture of ƒ2.8. The PureView stays at ƒ2.4 from wide to telephoto.

Nokia engineers figured the problem could be solved with a digital zoom. But digital zooms suck, making your picture like a tenth-generation JPEG. The trick was to make a sensor big enough that you could just cut a full-res picture out of the center. The Nokia folks figured that 5MP is big enough for a phone, and that a (roughly) 3X zoom would be just fine. Thus, they arrived at 41 megapixels.

When taking a shot, these pixels are crunched by algorithms and adjacent pixels averaged out to eliminate noise and achieve startling detail. When you zoom, it is done optically. But even the longest zoom is “capped” at 5MP, no lower.

The team was inspired by satellite imagery. The photos taken are super high resolution, but typically we only look at a small chunk at one time.

I zoomed in on some images taken with the camera and they really are amazing: very sharp at full size and showing a surprising amount of detail as you zoom in. You really get the feeling you’re in Google Earth, able to get closer and closer. I thought about telling the phone to “enhance,” but that was a little too dorky, even for me. Big printed photos from the phone also show very high-res pictures, with little noise, even at night.

Nokia wouldn’t say anything about future Windows Phone plans for this tech, but the hints were possibly even more intriguing. The company is looking at various ways of deploying the sensor. I guess this could include panoramas, HDR effects and so on, but given the cool factor of the current setup, I have high hopes for something even cleverer.

I just wish it was in the iPhone so you could do something useful with the picture once you’ve taken it.