HTC explains why 4 megapixels are better than 8

HTC says the "Ultrapixel" camera on its new HTC One will outpace the competition, despite having just 4 megapixels. Here's why.

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With its new flagship phone, the 4.7-inch HTC One, HTC has made the seemingly baffling choice of opting for a 4-megapixel camera, instead of an 8- or 13-megapixel unit of the kind seen on the high-end smartphones of its rivals. That doesn't seem to bother the Taiwanese firm, however, which insists that dropping the megapixel count on its "Ultrapixel" camera is "doing the right thing for image quality."

The Ultrapixel 4-megapixel sensor measures one-third of an inch, which is the same size as the sensors found in phones such as the 8-megapixel iPhone 5 or Nokia Lumia 920. HTC's gambit is that fewer megapixels on the same-size sensor means each individual pixel is larger, and therefore lets in more light and produces better photos in low-light conditions.

"I think it's just become a really easy sales metric," HTC's director of special projects Symon Whitehorn told me, explaining HTC's decision to sidestep the megapixel arms race entirely. "In the camera business it became 'more megapixels for the same money or less money' -- a very easy metric for consumers to latch onto."

See the bigger pixel

"It's a risk, it's definitely a risk that we're taking," Whitehorn acknowledged to me during a briefing. "Doing the right thing for image quality, it's a risky thing to do, because people are so attached to that megapixel number."

Each pixel on HTC's backside-illuminated sensor has an area of 4 square microns. By comparison, every pixel in the 8-megapixel sensor of last year's HTC One X had an area of 1.96 square microns per pixel.

"We've known for a long time in the imaging industry that increasing the megapixel count often increases the signal-noise ratio," Whitehorn says, "So we have a problem with more noise in those images, just because of the rate of sampling. That means that these images become noisier, the low-light performance falls off because you're not absorbing enough light."

My colleague Jessica Dolcourt's excellent guide to the megapixel arms race details this further. Gartner analyst Jon Erensen explains: "The light [goes into] the well and hits the photo-sensitive part of the image sensor, capturing the light. So if you make the wells smaller, the light has a harder time getting to the photo-sensitive part of the sensor."

Keeping smart phones trim

So if bigger pixels make for classier images, why do proper digital cameras still opt for so many megapixels?

The reason is that these larger gadgets can incorporate bigger sensors, which frees up more space for larger pixels. HTC doesn't want to increase the size of its sensor, for fear of bulking out the phone itself.

"If you grow the sensor any bigger to accommodate big pixels and a higher pixel count, you have to grow the whole camera," Whitehorn told me. Nokia's 808 PureView had a whopping 1/1.2-inch sensor, for example, but owners had to put up with a chunky camera unit bulging out of the back.

If another manufacturer deems bulky dimensions to be a worthy price for picture quality, however, HTC could see its new snapper quickly outpaced.

HTC's lower-megapixel trick is also no guarantee of capturing great pictures, as there are a slew of hardware and software factors that go into crafting a killer photo. Ultimately we won't know whether the Taiwanese company's gamble has paid off until we get the HTC One into our testing labs and compare its imaging prowess to that of other smartphones.

The pressure on HTC to produce a top-notch mobile has never been higher. After two years of watching Samsung devouring the company's slice of the smartphone pie, HTC is now faced with plummeting profits and the looming threat of Samsung's follow-up to the Galaxy S3. If the HTC One doesn't live up to the hype, it could spell further trouble for the corporation that first brought Android into the limelight.

Will the One see HTC win back the Android crown? What do you think of the company's lower-megapixel tactic? Do you think the megapixel race is getting out of hand? Have your say in the comments below.