There is no substitute for speed. Investing in a f2.8 lens is a must for any photographer working events, weddings or portraits. It gives you that extra stop or two of light needed to work in low-light situations. More importantly, it gives you shallow depth of field, so your subject pops off the background. If you are looking for a cost-effective, fast-performing lens, the new Tamron 24-70 f/2.8 zoom is a great all-around lens.