Sigma's DP1 is unusual for a digital compact camera, in that it has an APS-C-size sensor, as found in many digital SLRs.
Sigma has done an excellent job in keeping the Sigma DP1's wide-angle 28mm equivalent lens small, but there's a price to pay.
With a maximum aperture of f/4, the Sigma DP1 is slow for available-light photography. There's little ability to control depth of field wide-open for those compelling selective-focus shots. Be that as it may, the 28mm lens stops down to f/11 and is very sharp and well-corrected - there's little barrelling, and chromatic aberration is minimal. Still, if anyone reading this thought the Sigma DP1 was aimed at Leica users, think again. It's certainly no point-and-shoot, either.
Auto-focus is tardy, and while the Sigma DP1 has a nine-point AF system, this isn't automatically selected by the camera. You have to select the AF point from the menu, like you do for most choices, and it's not a particularly quick process.
Oddly, a dial to the rear is solely for manual focus. It would have made more sense if that control had doubled up as selector-dial for other features, like that found on the similarly specified Ricoh GRD II. The battery life and build don't match up to those of Canon's unstoppable PowerShot G9, but the Sigma DP1 is well-made, and the metal shell is preferable to the plastic-looking outer of the early mock-ups.
We like the Sigma DP1's uncluttered design, although the power button feels cramped when used with the optional-extra viewfinder. An optional lens adaptor is ideal for grads and polarising filters, and when they're not being used a square hood is handy for cutting veiling flare. This obstructs the view with the optical finder, but the combination works in the field.
Picture quality is exceptionally high for a compact, but noise levels aren't equal to the latest crop of sub-frame digital SLRs. Sensitivity runs from a low minimum ISO 100 to just ISO 800, but images look gritty and speckled in shadows well below that maximum. Left to auto, the Sigma DP1 easily overexposes scenes, so careful metering is necessary to prevent blown-out highlights.
To get maximum control over exposure, colour and detail, we found shooting Raw was preferable to Jpeg, but writing large files to SD cards is sluggish. It also means getting by with the Sigma DP1's bundled Photo Pro software, as there is no support for the DP1's X3F format files in Photoshop, Lightroom or Aperture at present.