Do mega pixels matter?

Today's digital cameras have already reached impressive pixel counts. The figures seem sufficient to generate high-resolution images, and even to withstand scrutiny in enlarged prints. A plausible case is often made that the mega-pixel wars are meaningless because digital cameras already have enough pixels.

The claim gains further support from an understanding that resolution is not determined by pixel count alone. In a photograph, resolution also depends on interactions among many other factors, including lens characteristics, low-pass filter response, noise reduction, and processing of contrast and sharpness parameters. By itself, elevating the pixel count doesn't necessarily lead to an appreciable improvement in picture quality.

Consider the 14MP direct image sensor used in the Sigma SD15 and Sigma DP1/DP2. Despite having a nominal 4.6 million figure for the number of pixel locations, this sensor produces images that are widely recognized as having excellent resolution.

Where resolution and realism meet

Still, Sigma thinks raising the pixel count is desirable and necessary to achieve the most natural image rendition. In digital cameras, the limit of resolution is determined by pixel pitch. When a certain level of detail (spatial frequency) is exceeded in a target object, the camera suddenly loses all ability to resolve it. This phenomenon is one reason why photos that include fine detail can end up looking unnatural.

As an example, say you are shooting a landscape with grass in the foreground and mountains in the background. The thin, closely spaced blades of grass are resolved correctly by the sensor in some areas, but exceed the limit of resolution in others. On the other hand, the ridges and surfaces of the mountains in the distance have a low enough spatial frequency to be resolved correctly throughout. In other words, the foreground would appear partially blurred against a consistently sharp distant background. A human observer would register the opposite: sharply defined blades of grass nearby, and hazy mountains in the distance.

This limit of resolution, which can be at odds with the human visual system, may be an unavoidable fact of physics. But Sigma believes innovation can make the problem so imperceptible that we can realistically pursue and achieve more natural image depiction. If so, we can look forward to being able to shoot images that are minimally affected by enlargement, and that retain a three-dimensional ambience even when viewed in small formats.

Further pursuit of high resolution is worthwhile not to win the pixel wars, and not even to make large-format prints. Rather, Sigma believes it is needed to achieve more natural photographic results.

30MP equivalent 'emotional image quality'

The 46MP direct image sensor of the SD1 is a breakthrough that triples the 14MP resolution of the sensor used in Sigma cameras up to now, while retaining the "emotional image quality" that is unique to a full-color capture system.

We enlarged the sensor to APS-C size (1.5x focal length equivalent), while narrowing pixel pitch, thereby dramatically raising the pixel count to 46MP (4,800 x 3,200 x 3).

The luminance resolution of this sensor is, in fact, equivalent to that of a 30MP CFA sensor as measured on the standard B&W resolution chart used in conventional digital camera resolution testing. With outstanding chrominance resolution that is free of low-pass filtering and color interpolation, Sigma takes a bold leap closer to the ideal, further enhancing the advantages of a direct image sensor. In terms of technology and image quality, this represents a significant advance.

Here at last is an image sensor for all who have ever dreamed of a digital camera breakthrough that can deliver the ultimate in image quality.

SIGMA SD1 Special Contents