[Canada_Rockies]

If one were to use the back focus AF button with shutter AF disabled, would tracking continue as long as the AF button was engaged? If that is a correct analysis, I know what I will be using from now on. I'm talking acquire focus with the AF button, and hold it.

[RobG]

If one were to use the back focus AF button with shutter AF disabled, would tracking continue as long as the AF button was engaged? If that is a correct analysis, I know what I will be using from now on. I'm talking acquire focus with the AF button, and hold it.

Interesting thought!

---------- Post added 23-10-17 at 03:11 PM ----------

For action, I use AF-C and Expanded Area AF, with the center point activated. For birds I use 25-point, for sports 9-points. Expanded Area is the only setting that will enable the camera's tracking algorithms to help you keep focus locked on the subject. I also find AF Hold helps with tracking. My default is AF Hold Medium. Do try it.

FWIW, I just tried 25 point AFC, expanded area AF (L) with the centre point activated. The rear AF button seems to trigger tracking, while half depressing the shutter release doesn't seem to, but I need to experiment more with a real-life subject.

[audiobomber]

OK, I'll need to do more research. From what I've seen in the interface, select mode selects a 9 point group from the 25 point matrix. I thought that it was still 9 points within the selected set.

If you look at the Expanded Area AF screens, you have Select S, M or L. The points the camera can use are shown in pink. The camera will initially try to focus with the point shown in red. You can move the red point around within the selected area. Some suggest to move it up for example for sports, to focus on a player's face instead of his jersey. When you half-press, the camera tries to find focus with the selected (red) point. If it does not find focus (i.e. if you do not take the shot), it will move to an adjacent point. Once you fully press, the subject is locked and tracked, by colour and shape.

OK, but you have to take a photo to start tracking? Half depressing the shutter won't do it? Sorry to ask so many questions, but I want to be sure that I understand it correctly.

Yes, thanks for questioning that. I mis-spoke above, and I have made a correction in my earlier post. You need to take a photo to initiate tracking. The subject is registered as soon as you take the first shot. For that first shot, you must ensure that focus is exactly where you want it, otherwise you will have a string of misses. As soon as you let up on the shutter button, tracking stops.

This post on "focus bumping" is useful for understanding how to use tracking. Note that in point #2, he sets sensitivity for the longest delay. That would be AF Hold High for Pentax. I've found that AF Hold Medium works well for BIF. I definitely needed AF Hold High for hockey: http://www.birdphotographers.net/forums/showthread.php/1949-Bumping-the-focus-for-BIF

---------- Post added 2017-10-23 at 09:54 ----------

If one were to use the back focus AF button with shutter AF disabled, would tracking continue as long as the AF button was engaged? If that is a correct analysis, I know what I will be using from now on. I'm talking acquire focus with the AF button, and hold it.

I never use the back button for action shooting, but back button AF behaves the same way as a shutter half-press.

I can see that BBF was useful at one time, because it would allow you to rapidly switch from AF-S to AF-C. I've configured User1 mode for action, which allows me to change many things (shutter speed, aperture, EV, SR, etc), when I switch from stills to action. I don't see any advantage to BBF, and it is more clumsy for me than shooting the way I am accustomed, i.e. half-press for focus, fully depress to shoot.

[Canada_Rockies]

I never use the back button for action shooting, but back button AF behaves the same way as a shutter half-press.

I can see that BBF was useful at one time, because it would allow you to rapidly switch from AF-S to AF-C. I've configured User1 mode for action, which allows me to change many things (shutter speed, aperture, EV, SR, etc), when I switch from stills to action. I don't see any advantage to BBF, and it is more clumsy for me than shooting the way I am accustomed, i.e. half-press for focus, fully depress to shoot.

BBF is my most used setting. I find it useful with slow lenses such as my 55-300 where I can obtain focus and then leave it there without the lens racking through the whole range each time I try to take a shot. Living in a cold climate means shooting with gloves on and that makes half press difficult.

[audiobomber]

BBF is my most used setting. I find it useful with slow lenses such as my 55-300 where I can obtain focus and then leave it there without the lens racking through the whole range each time I try to take a shot. Living in a cold climate means shooting with gloves on and that makes half press difficult.

OK, but surely you are discussing AF-S mode. I was talking about shooting action. Locking the focus depth would not be feasible for a subject that is in motion.

Do you have Quick-Shift on your 55-300? I used QS with my 55-300mm's more often than any other lens, especially when I only had 11 focus points. I find focussing much more precise with the K-3. The center point is noticeably smaller.

[Canada_Rockies]

OK, but surely you are discussing AF-S mode. I was talking about shooting action. Locking the focus depth would not be feasible for a subject that is in motion.

Do you have Quick-Shift on your 55-300? I used QS with my 55-300mm's more often than any other lens, especially when I only had 11 focus points. I find focussing much more precise with the K-3. The center point is noticeably smaller.

AF.C I hold the back button with my thumb. I have quick shift and use it often. That doesn't completely eliminate the hunting in AF.S or AF.C, though. I'm saving my pennies for the PLM version, but SWMBO is adamantly opposed to spending on camera equipment . I'll have to find something to give to her that is of equivalent value ....