4.2.2 v50010a gamma 1.6 - 1.8
4.2.2 v50010b gamma 2.0 - 2.1
4.4.2 v50018a gamma 2.2 - 2.4
4.4.2 v50020a gamma 2.0 - 2.1 AGAIN!
apparently v50018a is the best but checking with display tester not only the gamma but also the black and white saturation test... surprise!
the level of black and withe is the same!
i also compared gpad with my other tablet: asus memo pad hd 7 that have a much clear display and a gamma 2.2 - 2.4.
comparison side by side with display tester and a brightness comparable with 100% for gpad and 85% for asus:
asus go deep in black and white saturation test with more "seeable" blocks.
gpad: black 7 - white 250
asus: black 2 - white 254
only solution is the app "screen adjuster", with a contrast of -30 for gpad i have same results of asus in black and white saturation test.