The following information tells you what you need to do when Photoshop is managing the colours. Canon do not provide specific profiles for the Canon i850 and I have achieved the best results by setting the Print Space in Photoshop to sRGB.
This is the first Dialog window from which you need to select the Manual Colour Adjustment option and then click on Set. Then the ICM checkbox can be cleared for No Colour Management in the Printer Driver.
The final thing to remember is to always select the appropriate paper type in the Media Type drop down box.