Originally posted by normhead Naw, there isn't.
And then after you set if, what if your subject is the second or third object from the camera?
You answered my question and it's what I though it would be.
It's all in relation to the AF point and what is inside it.
If two subjects are in the selected AF area then my X-T3 will pick the closer of the two. So, as an extreme case, if I have the bleachers and a player in the AF area then my X-T3 will pick the player because I configured it that. It also means my AF area is
huge and I ought to make it tighter. Still, I will never get the bleachers. Ever. Likewise, if I have two kids standing in the AF area and one is further back then my X-T3 will focus on the kid standing closer. I honestly haven't used the Auto setting enough to understand its general behavior. In my photography I nearly always, always, always want the closer subject to be in focus. Forget the subject in the back. It's their fault for being in the wrong spot, right?
Now lets bring this back to the XF 100-400 vs D-FA 150-450 comparison. Despite the substantially lower build quality, less effective/intelligent OIS, and poorer optical performance I would say the lens with the X-T3 is can be more effective than a Pentax equivalent system in the same situation. The situation is "on the fly" AF-C performance at close distances with the lens at wide open or near wide open so DoF isn't providing a helping hand. Again, I'm not saying it's impossible to deliver great images with the Pentax. There are lots of examples here in the forum of awesome action. But, you aren't going to get a continuous burst of sharp images from it.
I'm almost afraid to reference this
but DPReview
has a pretty good assessment of the AF-C performance.
Fujifilm X-T3 Review: Digital Photography Review
Using full Auto settings resulted in lots of borked up images but tweaking them into a customized AF-C produced excellent results. You can scan through the 16 frames showing the performance of the customized AF-C settings and see every one of them is generally sharp. I don't know which lens they were using for that test - probably a longer zoom like the XF 50 - 140. The test was performed in a dark alley so the results could look better in bright sunlight. Remember, the sensor in the X-T3 has 425 on-chip PDAF points that span the entire imaging area. The processor in the camera is not starved for data.
Ok, ok ... I mentioned DPReview and I feel it's like using a curse word because of how they smeared the K-1.
How many times did they have to rewrite it to get the facts straight and how many times did they had to reshoot the studio comparison scene? Whatever could have gone wrong with review did go wrong.
I think the original author of the K-1 review didn't know left from right. The currently published K-1 AF-C test shows quite a number of lost shots and I've experienced those situations. I've also been fortunate to experience better hit rates than what is shown there.