Autofocus
Image: Having recorded 10fps sequences all morning using the 70-400mm SSM f/4-5.6 lens, I found the continuous AF works well, with roughly eight out of ten frames, including all in this sequence, having acceptable focus
Like the Alpha 55 and Alpha 65, the Alpha 57 has through-the-lens (TTL) phase-detection AF with 15 points. The points are arranged in three zones, each of which contains one extra-sensitive cross-type point. The number of points is class-leading, and indeed AF is very quick, even in low-contrast light.
Furthermore, offering continuous phase-detection AF during video capture and for high-speed burst modes means the Alpha 57 matches the performance of models that cost a lot more.
There are a number of useful autofocus options and tools available, including subject tracking, which latches onto the object closest to the centre of the frame, and face detection, which works well and stores faces in a register. When these faces are recognised in other scenes, they are given focus priority.
The camera also uses Eye-Start AF, which is a dedicated sensor that turns the EVF on when the camera is held to the eye and also switches on autofocus, so that the camera has already started to focus before the shutter-release button is pressed. Eye-Start can be deactivated, and indeed must be when the continuous AF setting is required.
