But if you already own the camera (or will get it soon) be sure to check out this easy graph that shows you the best lenses you can get for your A1 (Source: SonyAlphaBlog):
Sony’s necessarily bulky 50mm F1.2 G Master is feels quite a handful on a slinky mirrorless body but handling is nevertheless very refined. There are two customisable lens function buttons (nominally focus hold), a manual aperture ring with a switchable de-click mode, and a silky smooth manual focus ring which works a treat with magnified preview. Autofocus is fast and deadly accurate, while image quality is simply epic in every respect. There’s no denying it’s a pricey lens, but you get what you pay for and more besides.
And this is John Sison’s overview of the new lens: