That is precisely the problem/issue/yadda, Albert. I elaborated a bit in my 2nd post...
Quote: What I am expecting the camera to do in P mode is mimic the behavior of Tv mode when I am moving the Tv e-dial and mimic Av mode when moving the Av e-dial. It doesn't.
Take this example of a base exp. of 1/60s, f/4, ISO 100 and increase shutter to 1/90 and then 1/125. Aperture changes to f/3.5 and f/2.8 respectively. The ISO will not increase from 100 however, and so the shutter can not increase past 1/125s. Now if I change the aperture back to f/4 the ISO will now increase to 200 and the shutter stays on 1/125. I can continue to push the ISO by stopping down the aperture until the ISO maxes out and the shutter will not budge off of 1/125. And if I try increasing the shutter dial again it runs home to mama and I'm back to 1/60, f/4, ISO 100.
And, If I start with an exposure with ISO mid-range and decrease shutter, once aperture hits 2.8 it will decrease ISO down to 100 (yay!). But it will not then let me increase shutter again (boo!).
Easy to replicate: Put the camera into P mode and auto-ISO, focus and hit the green button to get a "correct" exposure (best demonstrated if the f-stop begins stopped down one or two stops). Now start increasing shutter speed. The aperture will stop down until it maxes out. Another click of the Tv dial *should* now start increasing ISO, but it won't. Your ISO
will however increase/decrease if the light changes in the framed image or you move the camera around thus changing the light.