Do more megapixels mean better photos?

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-colour 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 per cent 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] (203x254mm) 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 [Digital IXUS 900 Ti] at 10 megapixels vs. the [Digital IXUS 750] 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 colour management, the technology in image-processing engines," she said.

Panasonic, a newer entrant to the digital-camera market, also emphasises noise reduction. "Historically, you really had to make a choice between reducing image noise or preserving image detail," said Richard Campbell, 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.