Auto focus Tuning

Noticed a little while ago that my Sigma 150-500mm lens seemed to be focusing a little soft at the 500mm setting. Time to test the Auto focus. First I set up a scale in my studio and ran a series of pictures at all the zoom settings to see where the lens was focusing at each focal length. All looked good except at 500mm the lens was front focusing a little. So I adjusted the Auto focus in the camera to +5, then ran the test again and bingo that dialed it in just perfect. Here is a pic of the 500mm tape result after the adjustment.

Then I next set up a focusing target and ran a series of pictures at each focal length again. They all looked good. Here are the shots at 150mm and 500mm..

Then I went out into the field and shot the same series of pictures at a Forest Service sign that was about 25-30 yards away. The results were very good. A small spider web that was hanging on the sign even showed very sharp and clear. Here are the pics of the 150mm and 500mm test shots.

When all was done I was very pleased with the new Auto focus settings. To learn how to do this you can search it on YouTube and find a bunch of useful videos on the subject. Not all camera bodies support this feature, usually just the higher end camera bodies do. Read your owners manual to find out if yours does. Happy shooting!!