Aqui esta muy bien explicado el tema de bajar la gamma solo del IRE 5%

"I can also see 17 faintly without any adjustments to 5 IRE with gamma 1886. I think the point of raising 5% luminance is to make that near black detail more visible. On OLED tv's since black is truly black, near black (<1%) is very hard to see since it so close to total black. On a plasma or LED tv, 0% may be the same as 1 or 2% on our tv. So 1% on their tv would look like 2 or 3% our tv, and 3% is easily visible on OLED. So what is trying to be achieved is to make that less than 1% look brighter and thus easier to see the detail. So instead of having a flat 2.4 gamma between 0 and 5%, you are trying to create a gamma closer to 2 for 0 to 5% which makes that more visible. A way to test what is trying to be achieved is to put on that batman movie and pause. Now only pay attention to the dark detail. Flip between gamma 2.2 and 1886. Notice how there is more detail with 2.2 in the near black? That is what we are trying to achieve by boosting 5% luminance with 1886 and 2.4."