SLRs erode medium-format lead in sensor quality

It looks like Canon and Nikon weren't blowing smoke when they said their high-end SLR cameras will compete with medium-format digital cameras used almost exclusively by professionals.

Given the image quality advantages that SLRs with larger "full-frame" sensors have over mainstream and much less expensive models with smaller processors, one might have expected another quantum leap from costly high-end medium-format digital cameras with sensors twice the area of top-end SLRs. Not so, according to new DxOMark Sensor test results set for release on Tuesday by French test and measurement firm DxO Labs.

In the digital era, Canon's top-end SLRs give medium-format cameras a run for their money.
(Credit: DxO Labs)

The company tested image sensors from several medium-format cameras — the Mamiya ZD Back, Leaf Aptus 75S, Hasselblad H3DII 39 and Phase One P45+. These are the sorts of cameras used by fashion photographers and others who need lush tones, fine detail and lots of megapixels to handle big photos such as magazine spreads.

But none outperformed the Nikon D3X SLR, whose score of 88 gives it the current top rank on DxO's sensor tests.

These medium-format cameras' overall scores were lowered by their poor low-light performance, but these cameras are generally used by studio photographers with carefully controlled lighting, so that in and of itself isn't a big factor. However, even overlooking that, high-end SLRs were competitive on the other attributes.

"We had expected that given their large-size pixel they would perform much better on dynamic range and colour depth than digital SLRs," said spokesperson Nicolas Touchard.

DxO measures the sensor performance by examining RAW images, those that haven't been processed by the camera or software such as Adobe Photoshop into more convenient but limited formats such as JPEG.

Don't judge a camera solely by its DxO Mark score; many other factors ranging from price, autofocus and lenses are also highly pertinent.

And bear in mind that DxO only checked a handful of medium-format models, and not the latest ones at that. For example, Hasselblad has begun selling a 50-megapixel model and plans to release a 60-megapixel one in 2009, and Phase One offers a sensor housing that fits to medium-format camera body. Leaf's Aptus II backs employ even larger 56x36mm sensors and reach 56 megapixels.

Even in the film era, medium-format cameras were rarer and more expensive than 35mm film rivals. But in the digital era, the competitive dynamics have tilted more in favour of conventional SLRs, because the cost of producing image sensors gets dramatically higher as the sensors get larger.

These medium-format cameras' overall scores are lowered by their poor low-light performance, but these cameras are generally used by studio photographers with carefully controlled lighting. (Credit: DxO Labs)