Pneumatic Confusion

[Cyberguy34000]

Pneumatics are something that I thought I had a pretty good idea of how they worked, but as I'm reading more and more of the posts on this form I'm questioning if I know them as well I think I do. I'm considering proposing an arm design at tonight's meeting that involves 3 pneumatic pistons. One for the base, another for the elbow, and the final one for the grabber. As I understood it, pneumatics work by controlling the releasing of pressurized air to manipulate movable pistons which when they become pressurized, expand.

But is the process controllable enough to be used on something that needs a great deal of prison and control, such as a joint in an arm? Can you acurately control the joint of the arm or would it only have one of two extremes? Please help.