Can someone please explain what "digital technology" lenses are? Sony is branding all of their newer lenses as DT lenses, meaning they are optimized for the APS-C sized sensors, but what does this mean? What is the advantage? Reason I ask is because they have a 50mm f/1.4 prime lens, as well as are introducing a 50mm f/1.8 DT prime lens for less than half the price and I'm wondering which path to take... Thanks in advance!