The new Sigma DP1s is near-identical to its predecessor in terms of hardware specification, using a 0.98-inch, 4.7 effective megapixel Foveon X3 image sensor, a wide angle 28mm-equivalent lens with f/4.0 maximum aperture, and Sigma's previous generation 'TRUE' (or 'Three layer Reponsive Ultimate Engine') image processor. The company has only described two differences between the new DP1s and previous DP1 cameras.

The first is a firmware change which allows the DP1s' digital zoom buttons to be mapped so as to provide a Quick Set function, as seen on the newer Sigma DP2 and SD15 cameras. Sigma also describes performance of the camera when shooting backlit subjects as having been improved, but hasn't said exactly what this entails. If internet speculation is correct, the IR cut filter may have been altered to prevent an unusual flare-like defect that can sometimes occur in DP1 images containing a bright point light source, such as the sun, a candle flame or similar. Several examples can be seen by searching on Flickr - in the linked search, the 'Ballyholme Beach' and 'La croix d'Asnière' photos show it particularly prominently. At the current time we have no official information on whether the change relates to this issue or not, nor whether the change for backlit subjects mentioned by Sigma has been made in hardware or firmware.

The Sigma DP1s is expected to be available by the end of October 2009, and pricing has not been disclosed at this time. For more details, read our Sigma DP1s preview.