More megapixels, better photos: Fact or fiction?
Digital cameras makers continue to pack more sophisticated sensors. But some say there's a price to pay: lower image quality. Image: When photo noise annoys
- Shankland covered the tech industry for more than 25 years and was a science writer for five years before that. He has deep expertise in microprocessors, digital photography, computer hardware and software, internet standards, web technology, and more.
Digital camera makers continue to squeeze ever more megapixels into their products. But does that make for better pictures? Some experts say no. Image quality isn't improving, they say, and some fear it may actually be degrading as the megapixel race escalates.
"There is definitely a decrease in image quality," said Dave Etchells, editor of a camera reviews Web site, the Imaging Resource, which performs extensive camera tests. "There have been some improvements in semiconductor process technology for sensors, so it's mitigated the problem a bit, but there overall has been an increase in image noise."
The basic concern is that smaller pixels on camera sensors means less sensitivity to light, leading to image noise such as off-color speckles or rough edges, worse performance in dim conditions, and the loss of finer tonal gradations such as the subtle shadows of a white wedding dress. Point-and-shoot cameras, with their small sensors, are the chief culprits.
Camera makers disagree, saying consumers have an appetite for higher-resolution images--for making larger prints or cropping to focus on specific details--and that image quality has indeed improved overall. But even if they're correct, they have a growing perception problem among influential camera experts and enthusiasts.
Some of the blame can be laid at the feet of consumers, who fixate on megapixels as a measure of quality. It's the same thing that happened with PC processor megahertz and flat-panel TV dimensions. "The word 'megapixel' is a marketer's dream. Every consumer believes more is better," said Chris MacAskill, chief executive of SmugMug, a Web site that hosts photos and lets users print them.
"The trouble is megapixels stopped mattering once we passed 6 of them," MacAskill said. "One in a million shots would benefit from more than 6 megapixels, while every indoor shot would benefit from less noise."
Not so fast, experts
Canon, which market analyst firm iSuppli estimates sold 20 percent of the 96.4 million cameras shipped in 2006, sharply denies there has been any degradation of image quality with its PowerShot point-and-shoot cameras.
"When all else is equal, our 10-megapixel models tend to produce better detail than lower-resolution models at print sizes of 8x10 (inches) and larger," said Chuck Westfall, director of media and customer relationships at Canon. That holds true even while holding other factors constant, he added. "For example, it's fair to compare the PowerShot SD900 Digital Elph at 10 megapixels vs. the PowerShot SD550 at 7.1 megapixels because both cameras have the same lens and sensor dimensions," he said.
Sally Smith Clemens, a product manager for Olympus Imaging America, added that reputable camera makers are careful to improve image processing to ensure that the overall picture is good even if noise levels increase in a sensor. "It's not just the resolution of the sensor that determines the final image quality. It's optics, the color management, the technology in image-processing engines," she said.
Why increase pixel counts?
There are advantages to increasing the number of megapixels. Larger prints that require a minimum pixel count can be easier to make, and consumers can crop images to focus on just the subject matter they want.
But there are costs, too. Among the more obvious burdens: Camera image-processing chips have more data to digest; memory cards and hard drives fill up faster; and photo editing puts greater space, memory and time demands on computers.
More subtle problems also are possible. Camera image sensors rarely get larger from one generation to the next, so squeezing more megapixels out of a sensor means each pixel on the sensor is smaller. In most of the chip business, smaller electronics are dandy, but with cameras, they translate to less light per pixel.
That light difference means it's harder to distinguish the signals produced by light from the electronic noise in the sensor. The idea of making the signal-to-noise ratio worse may sound pretty technical, but possible consequences are easily understood: Images suffer from color speckles, and cameras work poorly in dimmer conditions such as indoors.
"If you try to cram more pixels into the same amount of space, you risk getting signal degradation because you're not getting as much light into the same pixel," said Chris Crotty, an analyst with iSuppli.
It can be tough for consumers to understand why they might not want to snap up the most megapixels possible. "People can understand the idea of more numbers is better," Crotty said. "But signal-to-noise, fill factors, dynamic range, blooming--these are concepts most people aren't going to understand."
--Stephen Shankland
Panasonic, a newer entrant to the digital-camera market, also emphasizes noise reduction. "Historically, you really had to make a choice between reducing image noise or preserving image detail," said Richard Campbell, Panasonic vice president of imaging for Panasonic Consumer Electronics. "However, Panasonic has made drastic improvements in reducing overall picture noise without sacrificing detail, specifically in its recent improvements in the Venus Engine 3 processor for 2007 models."
Image-processing chips, while more powerful and sophisticated in current cameras, can cause problems, though, as they try to remove noise.
"What you often get along with the additional pixels is more noise, which ends up getting smudged away oftentimes by in-camera noise reduction software," said Jeff Keller, editor of the Digital Camera Resource Page.
Keller recently advised most readers to pick the 8-megapixel Canon PowerShot A630 over the 10-megapixel A640. "Most people don't need the extra resolution. Plus, the file sizes are larger, and the camera is slower," he said.
Image sensor makers are also changing to try to deal with the noise issue. In particular, they're working on reducing the size of supporting electronics so more sensor area is devoted to gathering light. Compensation strategies include the following:
• Olympus began using "NMOS" sensor chips that decrease the area taken up by electronics, Smith Clemens said. And in low light, results from multiple pixels are ganged together, a move that averages out noise but reduces the ultimate image's resolution.
• Sensor maker Micron has technology to let multiple pixels share the same circuitry so less is needed, said Suresh Venkatraman, director of digital camera work at Micron.
• Canon said its image sensor pixel sizes shrank only "fractionally" when it moved from its 8-megapixel EOS Digital Rebel XT to its 10-megapixel XTi sequel, a move made possible by reducing the amount of space between the sensor pixels. (The company also said it improved the sensor sensitivity.)
• And Fujifilm's SuperCCD sensor grid is rotated 45 degrees compared with ordinary sensors, to devote more area to light-gathering, said David Troy a senior product manager at Fujifilm USA.
Do consumers care?
Having better technology and getting consumers to buy aren't the same thing. Fujifilm, for example, has technology that uses two sensors for each pixel--one for low-light sensitivity and one for brighter conditions.
"Those...cameras did a fantastic job with highlight detail," Chris Crotty, an analyst with iSuppli. "It was an admirable effort, but it really didn't get any traction in the marketplace."
But there's evidence of a more sophisticated understanding of the situation--in part the result of the fact that most digital-camera buyers aren't buying their first digital cameras. Among features camera makers are beginning to add to point-and-shoot models are face detection to set focus and exposure better, lenses that gather more light, and zoom lenses that work better with wide-angle views.
"Megapixels will always be important, but as consumers become more educated, it will be the addition of other features that make the purchase of their new camera more worthwhile," said Richard Campbell, vice president of imaging for Panasonic Consumer Electronics. "As the digital-camera market matures, consumers are becoming aware that lens quality, processor quality and image stabilization technologies are at least as important as pixel counts when determining image quality."
Even better, those features aren't mere marketing hype. "Face detection is a technology that has real tangible benefits to consumers," Etchells said. "You will get more in-focus photos and get the exposure right."
Don't expect an end to the megapixel race, though, Crotty said. The firm estimates that digital cameras had an average of 5.7 megapixels in 2006 and forecasts it will increase to 6.5 megapixels this year and to 9.2 megapixels in 2010.
SmugMug's MacAskill thinks that's a shame.
"We went past the point where more megapixels made a difference years ago," MacAskill said. "In the last 3 million prints we've made for very discriminating eyes, none were returned for lack of pixels."