Originally posted by Winder It does take a good bit of processing power, but the speed of the sensor has been the main hurdle. That is why Sony put the stacked BSI sensor in the A9. The speed at which the sensor can read all the AF points has a lot to do with tracking. The A9 reads and adjusts focus 60 times per-second. Then you have to have lenses that can move that fast. Canon and Nikon have developed predictive AF that works great on a subject that is moving at a set speed in a consistent direction. Sony has developed a reactive AF system and that works better for subjects that are moving erratically.
I would love to know how many times per second my K-1 is checking and adjusting AF.
Unfortunately companies only publish that kind of info, if they happen to be the best. With Pentax's aversion to be cutting edge i hardware, more of a do something special with like Pixel Shift with more available hardware, it's unlikely they'd do well in that test. I'd expect the whole Pentax system to be clocked slower, and not perform as quickly. Most of us can live with that.
That being said, I think the predictive focus slows down the whole process bit. Imaging resources on static subjects show the K-1 is slightly faster. Maybe not as good for shooting a burst of a moving subject, but better for a single frame static capture.
The shutter response lag time for a K-1 is .09s
http://www.imaging-resource.com/PRODS/pentax-k1/pentax-k1A6.HTM
For the A9 it's .216.
http://www.imaging-resource.com/PRODS/sony-a9/sony-a9A6.HTM
You can usually pick and choose stats to show your system is better. It's all about what you value and about using the system that gives you the best images at what you are actually doing.
I've actually noticed that out in the park, lying waiting for wildlife with 7 other photographers, none of whom shoot Pentax. Prefocused on a an Otter or a Pine Marten or whatever, when there's slight change in pose, when we are all prefocussed waiting for the moment, often, my shutter clicks first. According to IR, an A9 shooter will experience a longer delay after pressing the shutter button.
You always have to give something to get something.