Kit
On average I'd say it was six shots. I think if you used one of those calibrated rigs that you can buy to fit on your tripod you would probably take more. But doing it by hand/eye it can get difficult to make an adjustment and see the difference, even though my eyesight is pretty good. One thing I have noticed is that with liveview on the Canon 50D you can get much better manual focus, but it doesn't work with flash.