I have a unibody macbook pro 15 inch, 2.8 Ghz, 4gb ram, 500Gb HDD. There are various display settings like 1440x900, 1344x840, 1280x800, 1024x768 and so on till 640x480 (descending order). Will the battery consumption vary at different display settings? If so, how much of a difference will it make? Thanks in Advance.