From yesterday's track race....with the new Sigma 70-200 Sport.
f2.8.
Panning shot at f5.6 maybe...
F3.5...
F3.5....less than 100m to the finish...off turn 4th.
With a matching Sigma 1.4x converter..at 250mm f5. At F4, not all focal length produce the same sharpness...the soft spots are from 135mm to 185mm. By F4.5, you generally see better sharpness.