Here is a video comparison of new released Sigma fp compared to Panasonic Lumix S1 full frame mirrorless cameras. Both cameras used the Sigma 45mm f/2.8 DG DN Contemporary lens. From the video, we can see that Eye-AF of Panasonic Lumix S1 is much better than Sigma fp.
Sigma fp – Buy from B&H Photo Video/Adorama/Amazon
Panasonic Lumix S1 – Buy from B&H Photo Video/Adorama/Amazon
Sigma 45mm f/2.8 DG DN Contemporary Lens – Buy from B&H Photo Video/Adorama