Originally posted by Merv-O Reh: I agree with Marcjeerling on this one: the single point center is faster on the K-5 ii, as it hunts less. I use my 50-200mm and 50-300mm SMC lenses on the K-5ii because it sems both come form the same time period and while I can't prove this, it appears that the K-5ii makes these lenses shine. Again, tghat is purely anecdotal but that's what it seems like.
The center focus point of any camera is the fastest/accurate/precise one. New pro models or the sport oriented cameras have 3, 5 or more fast af points (usually dual cross type af) all of them being located around the center one to help photographers to track subjects with a group of 5 af points when the single one is not enough.
If I'm not mistaken, K1 has 3 cross type af points sensitive to f2.8 lenses (one above and one below the center point) so when you have the group of 9 af points activated, those 3 af points will be the ones that will first try to nail focus. That's why I keep an eye on cameras specs when I go out and test different cameras. Often people think that is enough just to change the af from af-s to af-c and af points from single to zone to get good results when shooting action. It's not and you have to take into consideration lots of things in order to get the best of the gear you have.
I also do simple tests at home by focusing on a small 3D object with the center af point activated and then I shoot again by selecting a different af point, but I make sure that the new af point selected can also be found when I select 5 or 9 af points. I do this test at 200mm f2.8 and also at f3.5 on a 70-200mm f2.8 lens for example so that I can have an idea based also on a specific distance if I have the subjects eye in focus with all af points. This way I know for certain when I go out and shoot action if the zone af (9 af points activated when you use K3 or K1) is suited or not at fast apertures for specific subjects. I know that there are DOF calculator programs that I can use, but I like to do my own tests because i like to practice rather than read/watch stuff on internet/apps.
That's why I said a few comments back that at f2.8 and with 9 af points activated it is more difficult to get the eye in focus and if you don't have the zone af with 5 af points instead of 9, it may be better to use single point af. It also counts how close to each other are the af points...
There are lots of tests that can be done and it takes some time to adapt the shooting style based on the gear you have, but if I have to shoot some action today with K1, my "problems" will be more related to fps and buffer rather than af. Comparing a sport camera with a field camera and setting a high standard for the field camera when comes to tracking doesn't help either when comes to enjoy shooting.