Originally posted by fevbusch Na, on my k30 (with DA16-45) lens is set to spot focus and camera is on AV mode.
You are confusing two completely different things. AV mode is an exposure mode and has nothing to do with focus.
Spot focus (center point focus) just uses the center, single focus sensor to lock focus. Spot metering on the other hand, along with multi-segment and center weighted, are metering modes that determine how much of the scene the camera's meter uses to determine the exposure.
AF.C, AF.S, AF.A are all focus modes and have nothing to do with exposure, or bokeh.
Originally posted by fevbusch You mentioned lens should be on A mode but there is no A mode setting on 16-45 lens.
Correct, DA lenses do not have an 'A' mode but some older lenses designed for film cameras do, but if they are in 'A' mode they work just like a DA lens. This really is not an issue with any of the lenses you mention, except maybe the Sigma which I'm not familiar with.
Originally posted by fevbusch Might it be because I have the camera set to Capture focus?
There is no such thing as 'capture focus', I think you mean 'continuous focus'? Which means the camera is constantly trying to focus as you move the camera, like when tracking a moving object. AF.S on the other hand focuses once and as long as you keep the shutter button half pressed does not change the focus even if the you or the subject moves. And again, this is a focus mode and has nothing to do with exposure.