Full-Scale Sensor | SIGMA DP2s : Special Contents

The bigger the film size, the better the image quality. That's common knowledge in the world of film cameras. Ever tried using a Brownie film camera to shoot high-quality photos? Then you'll have a vivid sense of the exponential increase in image quality as film size increases. Basically, the same goes for digital cameras. In other words, sensor performance being equal, the image quality of a digital camera is determined by the size of the image sensor, be it CCD, CMOS or any other type.

In the era of film cameras, both SLRs and compacts using the 35mm system used the same size of film, and image quality came down to lens quality and performance. There used to be compact film cameras that delivered high image quality despite their small body size, and those compacts had a large following among amateur photographers. When cameras made the switch from film to digital, however, it was taken for granted that DSLRs and digital compacts would use different image sensors.

At 20.7 x 13.8mm, the DP's 14-megapixel image sensor is SLR-sized. This is about 12 times larger than the 1- to 2.5-inch sensor, and 7 times larger than a 1- to 1.8-inch sensor used in a conventional digital compact. This generous size takes the DP2's image quality to a different dimension.

Picture this. Light traveling through a small lens is captured by a small sensor and turned into an image. Light travelling through a large sensor is captured by a large sensor and turned into an image. What’s the difference between these two images? Essentially, it's a difference in quality. In the case of the small image sensor, the image is magnified by a high ratio when it's printed or displayed on a computer screen. This makes it tricky to reproduce the dynamism and 3-D feel of the subject. The SIGMA DP does just that by using a large integral image sensor.

The small size of the image sensor used in a conventional compact digital camera explains why it captures rather flat, unmodulated images. If the image sensor is small, the focal length of the lens is short. The shorter the focal length of the lens, the greater the depth of field - in other words, the greater the range of distances over which the lens can focus.

The prosaic quality of the images captured by an ordinary compact digital camera is caused by the depth of field characteristic of a small image sensor: the lens focuses evenly on everything between the subject and the background, eliminating any cadence within the image. The DP2 and DP2s, however, have an SLR-sized image sensor, so their standard lens is equivalent to 41mm in a 35mm camera, and with an F-number of 2.8, it has a large aperture as well. This means you can utilize the kind of cool natural background-blur effects you would normally expect of an SLR.