M Sigma DP1 Review
by Chris Townsend
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Sigma says the DP1 is a 14.06mp camera. Open a DP1 raw file in Sigma Photo Pro software, which is provided with the camera, and the size will be given as between 10 and 18mb, depending on the detail in the image. Open the same file in Adobe Photoshop Lightroom and the size will be given as 4.6mp. What is going on? The answer lies in the sensor type and the definition of the word "pixel." "Pixel" can mean either the photo detector or the location of that detector. All digital camera makers except Sigma use Bayer sensors which, put very simply, have red, green or blue pixels (photo detectors) that are combined when a photo is taken to form an image. The pixel count is the total number of pixels on the sensor. Sigma uses a Foveon sensor that has three layers of photo detectors, each collecting red, green and blue colors. A section through each layer counts as one pixel location. Thus there are three pixels at each pixel location. How many pixels an image has depends on whether you take the photo detector or location figure. Each Foveon layer is 2688 x 1792 pixels, or 4.65mp. There are three layers so Sigma says there are 14.2mp in total. Others say that as there is one pixel location per three photo detectors at each pixel location and the image file size is 2688 x 1792 there are only 4.65mp.
Does this matter? Zealots on both sides argue passionately and interminably that it does. For those of us interested in the actual images, I don't think it's significant. In terms of quality, the DP1 produces images that are comparable to the 12mp Canon XSi/450D DSLR and far superior to those from any other compact camera, regardless of the number of pixels. How much the Foveon sensor affects this is debatable, but my view is that the sensor size is far more important. What's clear is that the DP1 produces images of a higher quality than expected from a 4.6mp sensor. Foveon devotees argue that Foveon sensors produce "better" images than Bayer sensors. I can't say that I can see any meaningful difference when Bayer and Foveon images of the same scene are processed in the same software.
- Introduction: Why the DP1 is unique.
- Description & Usage
- What's Good
- What's Not So Good
# WORDS: 3310
# PHOTOS: 23
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