The Sigma DP2 is closely related to the company's existing DP1 model, based around a 0.98" diagonal Foveon X3 image sensor, which has an effective resolution of 4.64 megapixels with full color measured at every pixel location. The sensor sits behind a 41mm equivalent fixed focal length Sigma lens, and offers ISO sensitivity from 50 to 1,600 equivalents.
The Sigma DP2s, meanwhile, is a relatively minor update to the DP2 design. Differences are largely restricted to firmware and software, with the sole notable hardware change in the Sigma DP2s being the imprinting of icons directly into several of the buttons, and a change of color from blue to red for the playback-mode screen printed icons adjacent to some controls. Firmware and software differences in the DP2s include a new power save mode, and an updated version of Sigma's imaging application, Photo Pro 4.0.
Sigma DP2 firmware version 1.05 and Sigma DP2s firmware version 1.01 both improve one specific function of the respective cameras, according to the company. Image quality at ISO 400 sensitivity is said to have been improved. No other changes are listed in the release notes for the new firmware.
Instructions on how to check your current firmware version, and how to upgrade the firmware, as well as the update file itself can all be found on the DP2 and DP2s firmware download pages.