Heres a handy little workbook made by kodak i stumbled upon, print it out, or just read along, i found it very useful in clearing up some very simple questions i had, good luck!
http://www.davidelkins.com/download/download_files/kodak/sensitometry_workbook.pdf
http://www.davidelkins.com/download/download_files/kodak/sensitometry_workbook.pdf
