[Nexus 5 Themes and Apps] mag01:
ok, do hopefully the last bit..

First, I'd like to say that the following isn't directly aiming to be the settings everyone should use. It's meant to be just a guidance for how do these settings work. For example my display isn't that much yellowish as many others seem to experience so there are definitely big differences among these displays.

Now in my previous tests I ended up with some (pretty much linear) green color rebalancing. I took it further then, also rebalanced blue and red a little so that they would match properly and also their levels would be correct (or much loser to that).

Green was a little tricky as it was visually very sensitive to incorrect changes - mainly not smooth transitions and slight banding were the result. So when performing bigger corrections I had to make some compromises to limit these negative effects.

Now this is the state after making all initial corrections (rebalancing color levels, but not targeting gamma corrections).

EDIT: just to explain this setup a little:

- red levels just corrected a little (minor corrections to get proper match with other color levels, more stable gamma progress)

- green levels taken down (maybe 8% in average, the main part was done in one of my previous posts, here I tuned this a little bit more like the red above)

- blue levels taken down (but not as much as green, maybe 2-3% in average)

R: 0, 10, 17, 27, 37, 45, 56, 72, 83, 101, 113, 121, 129, 123, 117, 104, 89, 77, 67, 61, 52, 37, 21

R delta:0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 1, 0, 0, -2, -2, -1, -1, -1, -1, -1, -1

G: 84, 85, 86, 88, 91, 94, 100, 108, 112, 122, 128, 132, 119, 115, 110, 98, 82, 71, 63, 57, 49, 36, 20

G delta: 13, 12, 11, 10, 10, 10, 10, 8, 7, 5, 4, 2, -2, -2, -1, -2, -3, -2, -1, -1, -1, -1, -1

B: 90, 91, 93, 95, 98, 100, 104, 111, 113, 122, 127, 131, 121, 116, 111, 97, 80, 67, 57, 48, 36, 29, 16

B delta: 4, 4, 4, 4, 4, 4, 3, 2, 2, 1, 1, 0, 1, 0, 1, -2, -4, -4, -4, -4, -4, -4, -4

Which gives me:

average gamma: 2.0

contrast ratio: 920:1

Now try to get gamma to about 2.1, delta values are difference to gamma 2.0 (above) so that they show only what's needed to correct for the gamma:

R: 0, 10, 17, 27, 37, 45, 57, 74, 85, 103, 116, 123, 127, 121, 115, 101, 86, 76, 67, 61, 52, 37, 21

R delta (gamma correction only): 0, 0, 0, 0, 0, 0, 1, 2, 2, 2, 3, 2, -2, -2, -2, -3, -3, -1, 0, 0, 0, 0, 0

G: 84, 85, 86, 88, 91, 94, 101, 110, 114, 124, 131, 134, 117, 113, 108, 95, 79, 70, 63, 57, 49, 36, 20

G delta (gamma correction only): 0, 0, 0, 0, 0, 0, 1, 2, 2, 2, 3, 2, -2, -2, -2, -3, -3, -1, 0, 0, 0, 0, 0

B: 90, 91, 93, 95, 98, 100, 105, 113, 115, 124, 130, 133, 119, 114, 108, 93, 76, 66, 57, 48, 36, 29, 16

B delta (gamma correction only): 0, 0, 0, 0, 0, 0, 1, 2, 2, 2, 3, 2, -2, -2, -3, -4, -4, -1, 0, 0, 0, 0, 0

Which gives me:

average gamma: 2.11

contrast ratio: 931:1

Now try to get gamma to about 2.2, delta values are difference to gamma 2.0 (above) so that they show only what's needed to correct for the gamma.

Note that I didn't go exactly to 2.2 as the display doesn't seem to perform that well after making such big corrections, and basically at gamma around 2.2. Some color transitions turn into just solid colors etc. And again, green is the most affected. I may try to add more exact 2.2 values later but now I've got enough of all this :D

You can also see that blue required slightly stronger corrections.

R: 0, 10, 17, 27, 37, 45, 57, 75, 86, 104, 117, 125, 125, 119, 113, 100, 85, 75, 67, 61, 52, 37, 21

R delta (gamma correction only): 0, 0, 0, 0, 0, 0, 1, 3, 3, 3, 4, 4, -4, -4, -4, -4, -4, -2, 0, 0, 0, 0, 0

G: 84, 85, 86, 88, 91, 94, 101, 111, 115, 125, 132, 136, 115, 111, 106, 94, 78, 69, 63, 57, 49, 36, 20

G delta (gamma correction only): 0, 0, 0, 0, 0, 0, 1, 3, 3, 3, 4, 4, -4, -4, -4, -4, -4, -2, 0, 0, 0, 0, 0

B: 90, 91, 93, 95, 98, 100, 105, 114, 116, 125, 131, 135, 117, 112, 106, 92, 75, 65, 56, 48, 36, 29, 16

B delta (gamma correction only): 0, 0, 0, 0, 0, 0, 1, 3, 3, 3, 4, 4, -4, -4, -5, -5, -5, -2, -1, 0, 0, 0, 0

Which gives me:

average gamma: 2.17

contrast ratio: 860:1

When compared to changing just the so called white point to 30, you'll get similar values:

WP: 31

average gamma: 2.07

contrast ratio: 900:1

WP 30:

average gamma: 2.14

contrast ratio: 870:1

WP: 29

average gamma: 2.23

contrast ratio: 870:1

And the progress of all color levels throughout the whole range is pretty good. So if you just want to change the gamma then you may be alright with WP set to around 30. Just you won't be able to correct the color levels this way.

When you change the WP value, colors change a little (as I mentioned in one of my previous posts), but change from 32 to 29 isn't that big and the changes will be minimal.

I mention the average gamma in all above cases, but it of course changes throughout the range and especially around 0-10% and 90-100% gray it's harder to achieve the correct value. However I tried to get the most stable results in all cases - but also didn't go too far to cause some visible artifacts to appear.

Again, this whole post (and also the previous ones) are more about finding out how this whole thing works so that some app with simple controls can be developed.

You may try my settings but they may not give you good results as your display might be very different.

Equipment used for measurements:

X-Rite i1 Display Pro with factory WLED LCD display type correction - colorimeter

Voodoo Screen Test Patterns 3.4 - Android test pattern generator

HCFR 3.1.0.4 - PC colorimeter software

Display Tester Pro - Android display tester