Originally posted by Larrymc my wired trigger doesn't focus with push of the button. I don't think any wired shutter releases do that on a K-3.
Originally posted by stevebrot If AF is turned on, half-press on a remote will activate the focus the same as with the regular shutter button.
I guess I should have explained that my comment was based on my experience with my wired remote (Bower-brand, reviewed
HERE). As noted by @Ex_Finn above, the contact surfaces on the 2.5mm TRS plug are coded for full-press (shutter release) and half-press (camera wake-up and AF). The scheme is:
Tip + ring 1 + ring 2 = full-press
ring 1 + ring 2 = half-press
Full-press and half-press work identical to the shutter buttons on the body or grip. I.e. the rules for AF-S, focus-priority and back-button focus are enforced. A long full press in "B" mode (option 1) will keep the shutter open for the length of the press. Pentax-compatible IR remotes, OTOH, work somewhat differently with supporting dSLRs. Behavior varies depending on body, menu settings, and model of remote. For IR remotes having a zoom (W/T) button, that button will often allow remote AF similar to back-button AF. Some IR remotes are incapable of emulating a sustained press for "B" mode (option 1). For those, "B" mode (option 2)* is necessary for time exposures. On the K-3/K-3II, AF on shutter release with an IR remote requires Menu/C3/19 be enabled.
All that being said, with the K-3II both full-press and half-press with a wired remote shutter release should activate AF if the camera is configured for other than exclusive back-button AF. I might also note that it is common practice to turn AF off when using a remote to avoid unintended change of focus setting during or before the actual exposure.
Steve
* Menu/C1/7 option 2 opens the shutter on first press and closes the shutter on a second press. This emulates the traditional "T" setting found on some cameras.