Hi everyone, Thank you for taking the time to read my post. First of all, I own a Canon 10D. I am now looking into a telezoom lens. I am deciding between the "EF 75-300mm 4-5.6 III USM lens" or the "EF 100-300mm 4.5-5.6 USM lens". aside from the obvious difference in focal length and aperature range. i don't know which one to pick, or which one is better? from looking at the obvious, it seems like the latter is not as good with a lesser range and aperature range, but the latter cost almost twice as much. please advise.. Thanks!