As promised, I have a review of a lesser expensive lens for you to peruse. There are a lot of good prime lenses out there for your Sony/Minolta camera, unfortunately, the Sigma 30mm F/1.4 EX DC isn’t one of them. This is an APS-C only lens, and gives the same basic view as a “normal” lens (50mm) on a full frame camera.
If you only care about the very center of your image, this lens may suit you just fine. If you want to carry this lens around for normal daylight shots, there are better choices. Ready to see what I’m talking about? Go here. People looking for instant gratification, go to the bottom of the page and read the final thoughts.