[Nexus 5 Themes and Apps] mag01:
Linear adjustments 1

So after some terrible madness here comes few linear adjustments.

The purpose of these is to provide description of how it works. In this case it's about getting a better idea of how to perform a linear adjustment of each color level throughout the whole range. This is useful for color balancing.

GREEN:

default:

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

-1.5%:

75, 77, 79, 82, 85, 88, 94, 103, 107, 118.5, 125, 131, 120, 116.5, 110.5, 99.5, 84.5, 72.5, 63.5, 57.5, 49.5, 36.5, 20.5

4, 4, 4, 4, 4, 4, 4, 3, 2, 1.5, 1, 1, -1, -0.5, -0.5, -0.5, -0.5, -0.5, -0.5, -0.5, -0.5, -0.5, -0.5

-3.5%:

80, 81, 83, 86, 89, 92, 97, 105, 109, 120, 126, 132, 120, 116, 110, 99, 84, 72, 63, 57, 49, 36, 20

9, 8, 8, 8, 8, 8, 7, 5, 4, 3, 2, 2, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1

-5%:

85, 86, 87, 90, 93, 96, 100, 107, 111, 121, 127, 132, 119, 115.5, 109.5, 98.5, 83.5, 71.5, 62.5, 56.5, 48.5, 35.5, 19.5

14, 13, 12, 12, 12, 12, 10, 7, 6, 4, 3, 2, -2, -1.5, -1.5, -1.5, -1.5, -1.5, -1.5, -1.5, -1.5, -1.5, -1.5

-7%;

87, 88, 89, 92, 95, 98, 102, 109, 113, 123, 128, 133, 118.5, 115, 109, 98, 83, 71, 62, 56, 48, 35, 19

16, 15, 14, 14, 14, 14, 12, 9, 8, 6, 4, 3, -2.5, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2

BLUE:

default:

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

-1.5%:

90, 91, 93, 95, 98, 100, 105, 112, 113, 122.5, 127, 132, 119.5, 115.5, 109.5, 98.5, 83.5, 70.5, 60.5, 51.5, 39.5, 32.5, 19.5

4, 4, 4, 4, 4, 4, 4, 3, 2, 1.5, 1, 1, -0.5, -0.5, -0.5, -0.5, -0.5, -0.5, -0.5, -0.5, -0.5, -0.5, -0.5

-4%:

93, 94, 96, 98, 101, 103, 107, 114, 115, 124, 128.5, 132.5, 119, 115, 109, 98, 83, 70, 60, 51, 39, 32, 19

7, 7, 7, 7, 7, 7, 6, 5, 4, 3, 2.5, 1.5, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1

-6%:

96, 97, 99, 101, 104, 106, 110, 116, 117, 125.5, 129.5, 133.5, 118, 114.5, 108.5, 97.5, 82.5, 69.5, 59.5, 50.5, 38.5, 31.5, 18.5

10, 10, 10, 10, 10, 10, 9, 7, 6, 4.5, 3.5, 2.5, -2, -1.5, -1.5, -1.5, -1.5, -1.5, -1.5, -1.5, -1.5, -1.5, -1.5

-7.5%:

98, 99, 101, 12.4, 15.4, 17.4, 20.4, 26.4, 27.4, 5.5, 9.5, 134, 118, 114, 108, 97, 82, 69, 59, 50, 38, 31, 18

12, 12, 12, 12, 12, 12, 10, 8, 7, 5, 4, 3, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2, -2

Notes:

1. Where is RED? Well, adjusting the red turned out to be quite tricky. it requires very strong adjustment to the near 100% values. It's really crazy as for example for the smallest correction (approx. 2.5%) first 7 numbers need to be corrected by about 30, then 8th number only by 5, 9th number by 3 etc. The difference between first 7 numbers and the rest is huge. Also, red levels can be only decreased as it's already at it's maximum. Therefore I decided to not do much about it at least for now.

2. Each correction has 2 rows:

1st row - raw values

2nd row - difference to default

3. What do the x.5 (like 118.5) values mean? In the lower half of the brightness range, any change of the numbers by just 1 makes big difference. As I wanted to perform even smaller corrections than what was possible that way, I took the advantage of separating the positive and negative register corrections. This way I could achieve these 0.5 steps when needed.

When I did this, I followed the following simple rules:

- Do not differentiate positive and negative register values by more than 1

- Always store higher level (not the raw value, but the actual level which is negated for the first 12 numbers!) in the positive register and lower level in the negative register

Few examples:

Numbers 1-12: correction from 100 to 100.5 = positive: 100, negative: 101

Numbers 13-23: correction from 100 to 100.5 = positive: 101, negative: 100

4. GREEN: first 1-2 numbers are usually slightly over-corrected then the remaining 4-5 which are otherwise corrected identically, the differences are like: +14, +13, +12, +12, ... why?

These are additional corrections based on visual tests (various test patterns) in order to reduce banding.

Here' I've made another simple rules:

-You can always do such additional adjustment to first 1-3 numbers, however only if it won't result in all these numbers being identical. That would happen to the blue color and that's why I haven't done it there. There must be at least a difference of 1 between these numbers!

- If making adjustments the opposite way (increasing levels instead of decreasing shown above) it's probably not necessary to perform these additional corrections. I'll maybe check it more later, now I;m quite sick of all this stuff. :D

5. Why there's only a decrease of each color described here?

Positive adjustments (level increases) can be performed almost identically, only in the opposite direction. I'll maybe test it more properly later, but now I really need to take a break. It was quite time consuming to perform all the above as the levels always fluctuate etc.. I've got some quite reliable method how to get reasonably stable results, but it takes a lot of time...