How does Sony a7r2 shoot silver?

Appropriately improve ISO, it is no problem to use 1600 for this machine, and speed is the priority. It depends. If you want to freeze the action, it is probably 1/500. If the static and virtual alternate, reflecting the fuzzy movement, you can use a vulgar shutter, such as 1/60 or so. Generally, the best time to appear is to use continuous shooting, and grasp the quantity in advance.