Underexposed

A correction was made to this story. See below for details.

DxO Labs, a French company with deep experience measuring cameras' technical performance, has launched a Web site called DxOMark.com that features detailed information on the performance of the image sensor at the heart of many higher-end digital cameras.

Many Web sites and magazines measure camera image quality with varying degrees of rigor, typically examining either the JPEG that the camera produces or a processed version of the camera's raw. But with its DxOMark Sensor measurement, DxO takes a new approach by judging the sensor performance based on the unprocessed "raw" image file from higher-end cameras such as SLRs.

That's significant, because raw images typically must go through a conversion process called demosaicing before they're useful for viewing. Most digital cameras capture only a single color--red, green, or blue--for each sensor pixel. Demosaicing fills in the gaps in this colored checkerboard pattern so each pixel gets all three color components, but this processing stage can disguise sensor performance.

The detail-obsessed camera crowd has begun eagerly chomping on the new data. On Sunday, there were 220 mentions of DxOmark on the Digital Photography Review forums, a popular location for impassioned technical discussions.

Nikon's D90 sensor beats out the one in Canon's 50D, judged on the basis of the raw files it produces.

(Credit: DxO Labs)

New tests coming
More measurements are coming, added Nicolas Touchard, vice president of marketing for DxO Labs' image quality evaluation business. First, in two or three weeks, will come measurements for medium-format digital camera sensors from companies including Hasselblad, Mamiya, Phase One, and Leaf. Then will come more high-end compact "bridge" cameras.

DxOMark Image Processing for the camera's computer, whose job it is to perform tasks such as converting raw images to JPEG, and DxOMark Optics for lenses.

The latter measurement will go beyond most lens tests by showing how well each lens works on each camera rather than one or two reference models. DxO takes that approach because lenses behave differently because different cameras have different attributes such as the geometry of the microlenses that help each sensor pixel gather more light, Touchard said.

DxO makes a business out of detailed measurements of camera performance, selling the data to camera and chip companies and incorporating it into its own DxO Optics Pro raw-processing software for photographers. So why give some of the data away for free on a Web site? Publicity.

... Read more