[Nexus 5 Themes and Apps] mag01:
[MENTION=4909585]gpvecchi[/MENTION]

I've got X-Rite i1 Display Pro. It's quite good, it's still just a colorimeter with its filters and limitations. Spectrophotometer would be better...

Anyway, let's start making some real adjustments...

Note that our target is color temperature 6500K and gamma 2.2

Have default values (I won't touch the white point so that will be omitted completely, also both positives and negatives will be kept at the same values):

RED: 0, 10, 17, 27, 37, 45, 56, 72, 83, 101, 112, 121, 128, 123, 117, 106, 91, 78, 68, 62, 53, 38, 22

GREEN: 71, 73, 75, 78, 81, 84, 90, 100, 105, 117, 124, 130, 121, 117, 111, 100, 85, 73, 64, 58, 50, 37, 21

BLUE: 86, 87, 89, 91, 94, 96, 101, 109, 111, 121, 126, 131, 120, 116, 110, 99, 84, 71, 61, 52, 40, 33, 20

Let's say these default values produce what's shown at attached GN5-default-grayscale.png - green is about 7-10% above the other 2 colors,

Because we can't get red color any higher around 100% gray level (e.g. white) - and even here you can see the red color level to relatively drop because it's already at its limit (see my previous post) - the only way how to start making some decent corrections is to lower the level of green (and then follow with correcting blue).

First, I'll get the green about 7-8% lower so that it will almost match the red at most points - see attached GN5-green-8pct-down-grayscale.png. You can note that as the red level relatively drops around 100% gray, this initial correction isn't going to be enough. However it's interesting to see this correction as it's the one of the few that have almost linear character - except for levels under 10% where no corrections were done as all color levels match and at 0% level (which is not shown in the generated graph) the blue is at the highest level (and you can't get it any lower as I mentioned in my previous post) and red and green match each other.

Values for green at this point are:

GREEN: 81, 83, 85, 88, 91, 94, 100, 108, 112, 122, 128, 133, 118, 115, 110, 99, 85, 73, 64, 58, 50, 37, 21

And the differences to the defaults are:

GREEN delta: 10, 10, 10, 10, 10, 10, 10, 8, 7, 5, 4, 3, -3, -2, -1, -1, 0, 0, 0, 0, 0, 0, 0

Comparison of measured levels (0 - 100% at 10% steps):

before:

R	0.204888	2.638356	8.436284	19.870841	35.196730	56.390184	81.874866	112.910127	145.260156	186.202236	223.400069

G	0.226465	2.633815	8.764019	21.142637	37.635424	59.959305	86.557503	119.314489	153.991908	197.972705	244.241854

B	0.486038	2.646776	8.091573	19.051200	34.135351	55.281188	80.610500	111.299997	143.495619	185.308541	231.698366

after

R	0.204634	2.633133	8.534870	19.882169	35.131096	56.384196	81.839302	112.785337	145.048755	185.639355	221.996512

G	0.228866	2.603693	8.506093	19.730305	34.482405	55.683435	81.367585	112.362997	145.689237	187.333797	234.812397

B	0.494311	2.652698	8.083512	19.049011	34.171195	55.614706	81.302708	112.535030	145.309045	187.821026	234.504451

Now I'll take a break, but later I'll follow with additional corrections. We'll adjust all 3 colors to match each other which will get us to the desired color temperature. Then we'll adjust the gamma to 2.2 by bending the curves towards the bottom. Everything is possible (not perfectly, but it it's quite good).

Note that this is just a demonstration of how things can be corrected via these numbers. If you perform the same corrections you probably won't get very pleasant result as there seem to be quite big variation in these displays.