DPI and megapixels basically have nothing to do with each other. The amount of (mega)pixels refers to the resolution of the sensor of the camera. DPI (or dots per inch) only has relevance for calculating print size, meaning the number of dots (think pixels.. not quite but sufficient for now) printet per inch. For example. Say you want to print a picture 10x8 inch. If you want it printed at 300DPI you'll need a resolution of 3000x2400 pixels (or 7.2 megapixels). But if you want to print that same picture at 150 DPI you'll only need 1500x1200 pixels which translates to 1.8 megapixels. Or the other way around, say the camera gives you 6 megapixels (3000x2000 pixels). Now if you print this image at 300 DPI the image will measure (3000/300=10, 2000/300=6.7) 10x6.7 inch. Were you to print this image at 600 DPI, the resulting image will be (3000/600=5, 2000/600=3.3) 5x3.3 inch. Both images will have the same amount of detail though, the only thing that differs is the printed size. Hope this helps.

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