Switch the A5100 to AF-C continuous autofocus though and Sony's hybrid system really shines. Like the A6000 before it, the A5100 will confidently track moving subjects across almost the entire frame, even when equipped with lenses like the FE 70-200mm f4G OSS. To put the A5100's AF system to the test I photographed a number of moving subjects from kids on scooters to adults on bikes and dogs running around. Below is a sequence of 16 frames taken with the FE 70-200mm at 200mm f4, and the A5100 set to Continuous AF and Continuous High / 6fps drive mode. Here's one frame, followed by the sequence.
Of the 16 frames, I'd say seven are perfectly in focus, with five more being very close, leaving the remaining four being slightly out when viewed at 100%. This performance was typical for the camera in my tests. So I was achieving about a 50% success rate for perfection and about 75% if I didn't mind it being a little-out. At 6fps this corresponds to 3 great shots per second, one that's okay and two which are a bit below average. I'd say that's still a good result, especially as most people won't be using the images at their full 24 Megapixel potential. The images are so large that you may rarely use more than 50% of the resolution, which in turn increases your effective hit rate.
The only camera which out-guns the A5100 without spending considerably more on a semi-pro DSLR is Sony's own A6000. The AF system is the same, but the A6000 can fire-off almost twice as many frames per second: 11 versus six. With a similar hit to miss ratio, this means the A6000 will typically deliver twice as many sharp images per second, giving you a stronger chance of capturing the decisive moment. Certainly if you're really into action or have sporty friends and family, then I'd go for the A6000 over the A5100. But don't let that detract from the A5100 which is a fantastic performer and will allow you to capture moments that literally elude other cameras in the same price bracket, especially rival mirrorless cameras and compacts.
It's also worth noting that while a good DSLR will match the tracking capabilities, it'll onyl do so if the subject is within a golden diamond shape which houses the AF sensor, roughly in the middle of the frame. if the action falls outside this area, the camera won't track it, whereas the A5100 and A6000 will track subjects right up to the edges of the frame, and also recognise faces and track them too if preferred. Plus, since it's natively live view, you can also exploit an articulated screen to compose at unusual angles - during a stage of the Tour de France I composed with the A6000 held out, but I also used it during the time trial to compose over the heads of crowds, all while still shooting with uncompromised AF and burst performance. I've detailed my experiences during the Tour in a seperate article:
shooting sports with mirrorless.
