I am a total newbie and am off to shoot some schoolboy cricket tonight, from about 6pm. I plan to have a go using the manual mode and on advice already received I am setting up as follows:- ISO 200 - Aperture f4 (I am using a Sigma 70-200 f2.8 with a 1.4 teleconverter attached) speed 640 - A1 Servo - Centre Point metering - Continuous Drive. I have been out into the garden and have pointed the camera at the grass and with the button half pressed I notice that the metering bar is not static but is constantly moving from the plus side to the minus side, is this how it should be? Amongst the many tips that I have read there was one whereby the setting were as per mine as given above but then the tipster went on to say that they then usually under expose by 1/3 or 2/3 of a stop. In order to achieve this am I right in thinking that I would just push the speed up to 800 or more leaving the aperture as wide as possible. I am using a Canon 50D by the way. Any help forthcoming before 5.30pm will be gratefully received. Many thanks. (Experts please go easy on me, I am a complete novice)