Originally posted by eyrr I have the K50 and never used the K3. I'm also trying to learn to use back button focus with shutter release button focus disabled. I was using my wired cable release for the fireworks on Canada Day and when setting up and doing test shots I noticed that focusing from the cable no longer worked for me either (and it previously did). Shutter release through the cable seemed to work, but not quite as reliably - but maybe that was me being out of practice. I assumed at the time that disabling focus from the shutter release had also disabled it through the remote port and only the back button (or manual focus) would work, but I haven't tested that theory.
I use back button focus all the time, I've developed a fondness for it. You are correct, it seems, that when using the camera set up for back button it does change the way the wired shutter release functions by disabling the wired shutter release half press to focus. I've got that little problem handled with a user mode set up for that. My new wired cable release releases quickly on remote button press but my older one would have a bit of delay for some reason. I had a problem with the fireworks shooting, I'm usually far enough away from the fireworks that I can set up for infinity focus by turning the focus ring to infinity and backing the focus ring back to a slightly closer setting but with the 55-300 PLM lens there are no marks on the focus ring. I just focused on a distant object and hoped for the best, things worked out OK. Luckily fireworks aren't a big focus challenge.
I think my confusion stems from before the time I started using the back button exclusively.