Compared to... Canon SD800 IS (IXUS 850 IS)

Below you will find a studio comparison between the Canon SD900 and the Canon SD800 IS at ISO 400.

Studio scene comparison (@ ISO 400)  

• Canon SD900 Digital ELPH: Program mode, ISO 400, Default Image Parameters,
  Manual white balance, +0.67 EV compensation.
  
  
• Canon SD800 IS (IXUS 850 IS): Program mode, ISO 400 , Default Image Parameters,
  Manual white balance, +0.67 EV compensation
  

• Lighting: Daylight simulation, >98% CRI

Canon SD900 (IXUS 900 Ti)	Canon SD 800 IS (IXUS 850 IS)
ISO 400, 1/500 sec, F3.5	ISO 400, 1/320 sec, F4.5
3,939 KB JPEG	3,028 KB JPEG

At ISO 400 the difference is less pronounced, but there is still a visible difference in the level of detail captured across the frame, and the SD900 looks cleaner (less obvious noise reduction) to boot. The larger sensor - though stuffed with 3 million more pixels - is obviously helping here.