Sigma have chosen not to do things by halves with the new SD1; after 9 years of incremental improvements in the Foveon sensor they've dropped a 15.4 x3 (46Mp) DSLR into a market dominated by 12-18Mp Bayer CFA sensor based cameras. This allows the SD1 to do something no previous Foveon camera has managed - matching the sensors almost pixel-for-pixel, then adding the full effects of coincident RGB capture. Adding to the recipe, the body is like no Sigma DSLR before - and packs dual-processors into a slim magnesium-alloy chassis.

The price of admission to this technology is high, placing the SD1 at the very top of the DSLR market. However, there's nothing that it can be compared to technically. Have Sigma chosen a path which is just too unfamiliar for the camera buyer of 2011, or is the SD1 an unmatched imaging tool waiting to transform the way people think about digital photography...

The SD1 is something of a reality distortion device, in that it's deceptively basic at first glance. It weighs just over 700g and has few buttons or external interfaces, it is slim in a way that brings to mind classic Olympus SLRs. Few DSLRs really match those dainty little film bodies of the '70s and '80s, but put the SD1 next to even an SD15 and it looks somehow more elegant. The design has stepped back from the utilitarian, functional SD cameras that preceded it and has become architecturally sophisticated, the base plate tapering (yet no deeper than a compact DSLR like a D5000 or K-5; it's not a visual trick to mask bulk). The grip has a flat edge and dominant scuplting, using the shallow body to good effect despite an overall depth similar to the SD15. The grip is also marginally slimmer than the SD14/15 design, lending a feel of space to the front of the camera.

The thumb location and control surface of the back is elegantly curved, reflecting the shape of a human hand. One of the less popular decisions on the camera, the removal of the top-plate LCD, gives space for a control wheel that can be turned in sweeping movements, rather than incrementally tweaked through an aperture in the body. With two wheels, a logical and intuitive layout of buttons has been adopted; a slightly clumsy looking exposure button (almost as large as, and next to, the shutter) makes astonishingly sound ergonomic sense as a single movement combines with the rear wheel to make adjustments to compensation easy. Similarly, AF point selection can be accessed both by the rear Function LCD setup and the direction buttons, or by holding the dedicated button on the rear and scrolling with the front wheel. The camera already looks sparse compared to feature-laden DSLRs, but if anything Sigma could have stripped it back even further and forced the user to rely on menu selections.

The LCD panel is 450,000 pixels, and has a good viewing angle. 

Mechanical controls follow the recent Sigma design, with Drive Mode and Program Mode wheels. Drive Mode covers single shot, continuous (7fps at the highest speed, lowest resolution mode - still a higher resolution than the original SD9 - or about 3.5fps in full resolution raw mode), timer delay of 10 or 2 seconds, Mirror Lock Up and Auto Bracketing. The Program Mode wheel no longer looks so sparse, having gained three Custom Mode positions. The viewfinder matches Sigma's previous offerings, with good brightness for an APS-C body and 98% coverage - the LCD strip shows frames remaining in the buffer as well as relevant information when making adjustments to ISO and Metering via the wheels. Whilst Sigma's original "Sports Finder" is still missed, the smaller prism leaves room for a decent pop-up flash.

The 11 AF points illuminate when selected, and the focusing screen has a pleasing texture, making judgement of manual focus easy. At the moment no optional screens are available.

The typically Sigma-quiet shutter offers speeds range from 1/8000th second to 2 minutes in Extended Mode, with flash sync at 1/180th (curiously reported as 1/200th in EXIF, a Bulb exposure in the wrong mode will also do this), the metering is 77-segment evaluative with four metering modes, there are 11 AF points. So far, it's a good camera, with improvements in every regard. Electronically though, this is a digital camera and the exposure-related aspects of operation are not yet half the story.