Yesterday I was shooting humingbirds and the weather was cloudy and crummy. To get a decent exposure I had to have my ISO between 800-1600, I had my shutter speed at 1/4000 to catch thier wings and f5.6. I was using my 75-300mm lens with a focal length of 271 and I was having trouble getting sharp focus.
Was this because of the high ISO? What setting could I have changed? I had the same issue today, same kind of weather so lighting was about the same. Would love some advice.