I am going through realigning my lenses due to change in shooting habits. I just sold my SEL50 - it was a wonderful lens that I barely used due to FL that was neither here nor there. If I need to carry a 50mm lens in my bag only for occasional portraits, might as well use a far cheaper manual lens. I also find that I am using 16/2.8 a whole lot more than I thought I would be. Basically because it's wide (and can be cropped if needed), it's very portable, and it has decent colors. So, I am thinking of maybe picking up a SEL20 for an upcoming trip to Prague. By all accounts, it's better than 16 and some say it's sharper in the center than Sigma 19 (but loses in the corners). It's also a pancake, something I've come to appreciate. Also, I should be able to slap the UWA adapter from 16 on it and get a 15mm FOV. So, the question is, how does it really compare to Sigma 19, Sony 16, or Sony 18-55 at 20mm ? Is it going to be a noticeable difference up to f5.6 ? How good / bad is it wide open ?