Right, I've been posting about this (annoying) behavior on K-3 and K-1. In short, there are two workarounds that seem to work:
1) If your lens has an aperture ring, take it off the A position and control the aperture using the ring rather than from the camera body. (Don't forget to also enable "Using Aperture Ring" in the custom menus, or the camera may refuse to fire.)
2) Set the camera to TAv mode and control ISO by setting a very narrow range of possible values - like say from 200 to 250 if you want to shoot ISO 250. (Note that the ISO setting will flash red because the camera mistakenly thinks the shot will be underexposed. Also, I don't think you'll be able to shoot ISO 100. It will bottom out at ISO 125, with a range of 100-125.)
At least with my K-3, both of these methods cause the dimming of the screen to be disabled. Here are the two previous threads about it:
one and
two.
Last edited by Doundounba; 05-04-2016 at 04:59 AM.