On Saturday I shot a Division III college women's soccer match for the first time this Fall. It was a bright sunny afternoon for the most part and I was able to shoot my EOS 7D and 70-200mm f/2.8 lens at lower ISO settings than when it's cloudy or the match is under the lights.
On checking my images later Saturday evening I noticed that the distant shots at 200mm were extremely out of focus. Shots at 200mm not so far away were not as bad. I noticed that distant subjects with this camera lens combination were also not focused correctly from Friday's tugboat roundup shoot.
Here is a screen capture of one of the out of focus shots. The image is zoomed in at 50% and the red box is the active center focus point that focused the lens. Obviously a problem existed as the plane of focus is far behind the focus point.
Sunday I did some testing and, of the possible plus or minus 20, I needed to set the micro focus adjust on the camera to minus 18 to get accurate focusing on the long end with distant subjects with this lens. I'll seed to do some followup to see how the focus is affected at shorter focal lengths and whether the problem exists with other camera bodies.
Here are some shots that are mainly in focus since the distance to the subject was less.