This was a simple autofocus test with my Lumix S5, Sigma 100-400mm F5-6.3 DG DN on a tripod. My model was walking towards me at a normal speed as I was zooming out from 400mm to 100mm and reframing. Out of 14 shots 4 were out of focus for a 70% hit rate. This was the first time doing this test and I expect I can do better with some practice and changing my settings. Settings: Auto Focus: Continuous, 1 Area, Drive Mode: Single. I would try Human Detect and Tracking for AF area and LVH (Live View High) for Drive Mode doing this again. Still, I got a 70% hit rate so any higher would be fine.
I wonder how eye detect will work when sunglasses?
I opened all the raw files in Photoshop and added the ISO, mm, F, and shutter speed in the top left corner, resized to 10″ and 75 dpi and save as a jpeg.
Based on this small sample, the AF works fine for me, though I plan to test out the other modes.

f8 blurs the background adequately.

I did not see that kid in back until looking at these pictures on my computer.

Should pay better attention to my backgrounds next time.

Stepping into the center

Out of focus

Still at 400mm

Still at 400mm

Starting to Zoom out, 317mm

296mm

245mm

Out of focus, 219mm

136mm

107mm

100mm
