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Introduction:

The Sigma DP2 Merrill is equipped with Foveon’s APS-C sized 46MP X3 sensor, packed into a compact body with a superbly matched fixed lens. The DP2m is one of three DP Merrill cameras, each of which have a different fixed focal length lens, but all sharing the same unique sensor. The DP2m comes with a 30mm f/2.8 lens, approximately matching the FOV of a 45mm lens on full frame 35mm cameras, and is positioned neatly in the middle of the DP Merrill focal length line up; The DP1m has a 19mm f/2.8 lens, while the DP3m has a 50mm f/2.8 lens.


The Foveon X3 Sensor uses a 3-layered true colour capture system, which basically leaves each pixel capable of recording the red, green and blue colour information of the light hitting the sensor. Most common image sensors have a Bayer colour filter array above a monochromatic sensor, consisting of 50% Green, 25% Red and 25% Blue pixels. After the image is recorded, sophisticated processing and interpolation is required to achieve a full colour image. While these interpolation methods are remarkably good, the level of definition, clarity and resolution is not comparable to a similar resolution true colour sensor design such as the Foveon sensor. At the end of the day, an image taken with a Foveon X3 sensor will give better colour and detail definition to that from a Bayer type of the same megapixel count. The added benefit of the Foveon sensor is the lack of colour aliasing which is inherent of the interpolation used in Bayer type sensors.


The images from the DP2m are sometimes hard to believe, and are a real detail feast to the eye. The sensor does require good exposures and good amounts of light. It doesn’t fare well in poor light, and the camera needs to be shot at ISO 100 or 200 for the lowest noise levels. In comparison to similar sized and resolution bayer type sensors, the output from a Foveon sensor is inherently much noisier in shadow details, poor lighting conditions, and high ISO images. Colour retention in the shadows is very poor due to high levels of chroma noise, and from ISO 400 and up, images can show blotchy colour. Sigma’s Photo Pro software, kindly desaturates these darker shadow areas, which in my opinion results in a very nice look, but the results from Iridient Raw Developer probably come closest to showing the truth of whats happening in the shadow details...


My largest motivational factor for buying the DP2m was, that the Foveon sensor can shoot B&W images with colour filters, and this without the loss in image quality. With a Bayer filtered sensor, shooting with a red filter will give truly poor results, since only 25% of the sensor’s pixels had the capacity to recorded the light which passed through the lens. The rest is interpolated. The ability to shoot in B&W with colour filters, while maintaining image quality, is simply a fantastic feature for me. I have long wanted a B&W only digital camera, and the Sigma DP2m can provide this. True B&W sensor cameras have been around for a few years already, and are basically normal sensors without a colour array on top of the pixel sites.  However, these were/are niche products, and are hard to find and/or quite expensive. I speak under correction, but I think of the first few commercially available true B&W sensors were medium format digital backs. Today, Leica and Phase One are the only camera brands I know of that sell a product with a B&W sensor; The Leica M Monochrom and the Phase One IQ260 Achromatic digital back. I can’t afford either by very long margins...




Sigma’s marketing fluff endlessly claims that this Foveon X3 sensor has a resolution of 46 megapixels. It doesn’t. The sensor has 15,3 million photo-sites, and the fact these do the work of 46 million in recording red green and blue, doesn’t mean that the image should be interpolated to three times the total pixel count. Interpolated to 46 MP, the results don’t compare favourably at all to bayer sensors of a similar pixel count. Comparing the 14,75 MP (effective pixels) output of the Foveon X3 sensor with the output of a 15-ish MP Bayer sensor, will clearly show the advantages of the true colour sensor. The Foveon sensor’s output will be unmatched in pixel level clarity and colour resolution, and besides this, it won’t have any interpolation colour artefacts such as those seen from bayer interpolated images. However, the Foveon sensor has some inherent difficulties with colour separation and colour accuracy due to the nature of how the silicone wafer absorbs light, cross contamination between colour layers, and extravagant processing required to output colours in a normal colour space.


On the right is a diagram depicting the colour absorption of the X3 Foveon sensor silicone wafer, along with the sensor’s layered sensor stack.

At the end of the day, the Sigma DP2m is a serious compact camera, capable of truly astounding images, with very high spatial resolution. The 30mm f/2.8 lens is also perfectly matched to the sensor, delivering excellent results from f/2.8. The camera design is refreshingly simple, and it feels solid and well built. It’s shaped like a small brick, and isn’t littered with buttons. The light weight of the body makes it easy to carry all day without the thin neck-strap cutting into the neck. The menu system is neat and simple, and luckily doesn’t have any cheap frilly features found on so many other cameras.


The DP2m, and the other DP Merrill camera alike, have some serious quirks and drawbacks. The decision to buy one needs to be very deliberate and well researched. It’s definitely not a camera for all situations, and is very much a one-trick pony that really excels at what it does best.