I was comparing pictures of my friends Camera a Nikon D200 & My Canon EOS 400D. My Pixels Width & Hight are 3888 X 2592. His Pixels are 3872 X 2592 so much the same. However the DPI is very different. My pictures are all 72 DPI. His are all 300 DPI. Why aren't mine the same? My picture setting is highest quality & fine. My card says about 450 pictures can be taken on a 2 Gig card. His says about 200. Help.