To apply the gain and offset sets you have to press the ok button on custom 1. Do the same with the gamma.
The posts refer to iris 3. This regulation is for one who likes bright images.
I discovered that hdmi enhanced disturbs cinema 1, so I changed to auto. The brightness I upped to 0 and decreased contrast to O. Finally I had the Iris in 1.
This is a question of taste. My room is very dark and light controlled. I'll keep this set up (user 1) for every source of video. I kept also Art's setting in cinema 1, that's proper for iris 2.
Anyway, tweaking a little,as I did, you will find the best image for you. I'm sure of this.