[Galaxy S II General] puremind:
While we really like the AMOLED+ display for its deep blacks, it also has major flaws:

- Severe black crush (loss of shadow details in dark scenes) when power saving is disengaged (which is the only way to obtain decent brightness)

- Greenish white, which becomes bluish after a few weeks of operation

- Oversaturated greens

- Loss of brightness after a few weeks of use

- Yellowish areas on the screen produced by the deterioration of AMOLED cells through heat, particularly prominent for gamers and overclockers

I wanted to run a few measurements to better understand what could be done at the software level to alleviate those issues. I am listing my findings below, following which I make a few recommendations to Samung, developers and users of the SGSII.

Findings

1. The maximum light outout with "Auto Adjust Screen Power" is limited

Note that the "Auto Adjust Screen Power" option is different to the automatic "auto-brightness" option. All measurements were made with auto-brightness deactivated and maximum brightness.

After measurements the results are as follows:

- Film Mode: 147cd/m²

- Standard Mode:149cd/m²

- Dynamic Mode: 147cd/m²

The lower value in film mode is due to the limitation of green and blue in film mode, which typically produce more luminance.

The lower value in dynamic mode is due to the picture becoming bright too fast above 50% brightness, there is actually white crush happening, as the Power Saving mode is trying to cap power consumption. This is similar to what is observed on a plasma, where Power Consumption is throttled

2. Disengaring the "Auto Adjust Screen Power" option (this is different to the Auto-Brightness option) significantly increases the brightness output

Not many people suspect the impact that "Auto Adjust Screen Power" option has. Engaging that option provides for much higher bighthness (at the expense of battery life):

- Film Mode: 276 cd/m²

- Standard Mode:285 cd/m²

- Dynamic Mode: 283 cd/m²

This is of course is at the expense of battery life but is still useful when trying to read in the sun. Unfortunately, as we will see later, this has a negative impact on shadow details and is not recommended for film viewing.

3. Light output diminishes though intensive use

The measurements after 3 weeks of use consistently show a deterioration of the maximum brightness over time.

Power Saving Engaged:

- Film Mode: 145 cd/m² (-1.4%)

- Standard Mode:147 cd/m² (-1.4%)

- Dynamic Mode: 145 cd/m² (-1.4%)

Power Saving Disabled:

- Film Mode: 270 cd/m² (-2.2%)

- Standard Mode:278 cd/m² (-2.5%)

- Dynamic Mode: 276 cd/m² (-2.5%)

I will continue to monitor this and post updated results in a few weeks.

4. The white balance exhibits a green push, which progressively becomes more bluish over time

I remember finding the whites greenish when I first got the phone. After 3 weeks, I wasn't bothered that much, they looked more neutral to me. I decided to test again after 3 weeks of use. The results confirmed by observations:

- Color temperature shifted after 3 weeks of use, with the proportion of blue increasing at the expense of green

- The color space after 3 weeks displays less saturated green

White balance at unboxing (green push)

White balance 3 weeks later (blue push)

3. Standard and Dynamic mode have the same color space. Film mode exhibits less green oversaturation

Dynamic/Standard Color Space:

Film Color Space:

4. Film Mode with engaged Power Saving has the best gamma

The dynamic mode has got a skewed gama with a white crush

Film Mode offers better gamma

Disengaging power saving creates black crush

When power saving mode is disabled, the loss of shadow details in dark video sequences becomes even more prominent:

As an example, I am including the gamma curve for the least faulty Film Mode with Power Saving disengaged. The much increased light output we saw earlier is at the expense of shadow details:

Recommendations to Samsung

The display clearly has a lot of potential:

-True blacks

- Large color space

- Very good maximum light output

- Standard Mode gamma is pretty linear

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Unfortunately, these qualities are poorly exploited:

- Gamma is overall too high at lower stimulas. Black crush is happening in any mode, thought at various degree

- White balance is biased toward green and blue, which leads to very high color temperatue. Whites are greenish on first year, evolving toward bluish with increased use.

- The color space could be toned down further. Even in film mode, the greens are too saturated

What Samsung could easily do:

- Further reduce light output in film mode by removing blue and green - this would allow for a color temperature of 65K

- Correct the gamma issues: a simple gamma control under the screen settings allowing to shift gamma incrementally across the whole bightness spectrum would allow very decent results indeed

- Although this has less of a priority in my book, allow a color space with further reduced green saturation.

Recommendations to Android Developers

Develop an app allowing to control:

- Bightness

- Contrast

- Gamma

- If possible for each individual color channel

Such an app would be beneficial to all smartphones on the market!

Recommendations to users

- Use the film mode when watching videos in order to avoid black crush, oversaturation and high color temperature. It is still far from the film standard, but will yield the best viewing experience

- Do not disable power saving mode or you will experience significant black crush. Only do so when viewing in bright environments where contrast is more important than accurate gamma.

Closing thoughts

It is obvious when looking at the numbers, that Samsung have struggled to throttle power consumption on the Galaxy devices while still maintaining brightness comparable to the iPhone 4:

When users reclaim more brightness by deactivating power saving, they indeed get nice peak brightness, but this is at the expense of the darker areas, which lose shadow details in order to limit power consumption.

Many users would be happy with an inbetween solution, with brighness around 180cd/m² but more accurate gamma