Nexus 6P display measurements, standard mode

With a comparison between maximum brightness and approx 100 cd/m² in order to evaluate the calibration curves scaling.

Average gamma values:
Max (366 cd/m²): 2.37
100 cd/m²: 2.32

Short analysis today due to lack of time:

– The curves, measured with a 256-precision are smooth which indicates the absence of banding in the grayscale.

– The color gamut is extremely large, and color saturation is increased further by the higher gamma: as you can see in the CIE 1932 diagrams, the saturation points are not spaced evenly.
Visual inspection of shows color clipping due to the color processing present to increase color saturation.
Boosting color saturation on such a wide-gamut display is undesirable.

This is the first Nexus AMOLED device boosting color saturation. I wonder if it's intentional or something inherited from the panel supplier default setup.
The color saturation levels are so extreme that I would qualify this color rendition behavior as a bug and encourage to file it as such.

– On slightly lower brightness levels like measured at 100 cd/m², the shadows on this unit become a lot darker, quickly reaching below the minimum the i1 Display Pro sensor used here can read.

– Grayscale RGB levels tracking on this unit is better at 100 cd/m² than at maximum brightness.
This is the reverse of older AMOLED brightness scaling I had experience with, where maximum brightness was the most accurate.
This may vary between units, but it's worth mentioning that lower brightness levels doesn't necessarily equates to reduced color accuracy.
Although this remark is valid for midrange and highlights, the situation tends to degrade in shadows.

– RGB Levels:
Red is lacking.
The colorimeter here can't see things exactly like your eyes: a correction would be required due to the AMOLED spectral characteristics but it still gives an idea with red lacking compared blue and green, compared to a standard target of Natural Daylight D65, which is neither yellow, blue or green, nor warm or cold but average daytime neutral white.
Since our vision is most sensitive to green, it is apparent.
Also since the color temperature formula, giving a warm/cold indication essentially ignored the green component, it is not reflected in the grayscale temperature curves values.

The decision (or oversight) to boost color saturation using color processing by default really leaves me perplex.
Measurements confirms my subjective first impressions 😉

#supercurioBlog #display #color #measurements #analysis


In Album Nexus 6P #1 display measurements, standard

Source post on Google+

Confirmed: Chromecast audio analog output is 48kHz 16-bit today

I gave a hand to +FrAndroid​​​​​ +Manuel C.​​​​​ to explore the audio capabilities of the Chromecast audio.

Google confirmed what we found in measurements earlier: Chromecast audio resamples everything to 48 KHz 16-bit for both the optical and analog output.

– It is a poor default choice for audio since most material is sampled at 44.1 KHz.
– The resampler itself is not so great, introducing various distortion artifacts.
– The 16-bit output limitation is not welcome, including for 16-bit material since the volume control is software and digital.
– And it prevents playing 96 KHz 24-bit material without loss of quality.

Google say they are working on it, however they didn't adjust their marketing material announcing the support of 96 KHz 24-bit resolution which is rather unfortunate.

I have a lot more measurements and data than the graph +FrAndroid​​​​​ republished, would you like to see them?

#supercurioBlog #audio #measurements #chromecast

Test du Chromecast Audio, le parfait compagnon de vos oreilles – FrAndroid
Après avoir rendu intelligents les écrans les plus basiques avec son Chromecast, Google a souhaité aller plus loin cette année avec le Chromecast Audio, un

Source post on Google+

+Vincent Sergère review of the Nexus 5X for +FrAndroid

Even in case you can't rely on translation from French, take a look at the +GameBench stuff!

He also sent me the measurements, made with my software #SensorMaster of two units, one of which have a lot more yellow white point than the other so that was interesting to have the full data on that.

First unit (more blue): 432 cd/m² maximum white point, 1326:1 contrast ratio
Second unit (more yellow): 495 cd/m² maximum white point, 1527:1 contrast ratio

Interesting discrepancy, because it also means that the yellow one could absolutely be re-calibrated to match the more blue one both in white point, contrast ratio and maximum brightness!

#supercurioBlog #measurements #Nexus #Nexus5X #display

Google Nexus 5X
Le Nexus 5X, issu de la collaboration entre Google et LG, est un terminal qui plaira forcément aux amateurs d’expérience Android pure et notamment aux possesseurs d’un Nexus 5 qui ne veulent pas d’une diagonale d’écran trop élevée. Face à son prédécesseur, le Nexus 5X a beaucoup évolué, notamment sur sa partie photo qui devient enfin utilisable avec des clichés de qualité mais aussi avec son autonomie, même si cette dernière reste encore un peu e…

Source post on Google+

Here's the results of the current state of my display calibration algorithm on the early batch Nexus 5 I sent back and its refurbished replacement

Following up on

On both, a 12-bit RGB LUT is loaded in hardware, but as you can see on the curves in these graphs, the panel being only 8-bit, there's some banding going on.
I started working on another driver approach that allows to avoid this 8-bit limitation and permits extremely precise correction.

The target for both is D65 white point (as seen by the sensor for simplification), gamma 2.2 curve with a fine-tuned near-black response to avoid clipping or visual artifacts in shadows and near black, also preserving the color balance as much as possible near black.

The replacement Nexus 5 stays better even when both are calibrated thanks to its higher native brightness, slightly higher contrast ratio, and better consistency in its RGB channels which requires less correction.
Although beside the brightness difference which is appreciable, they look the same.

On both, the grayscale Delta E stays below 1 which is a very good accuracy despite the current 8-bit per channel driver hardware limitation.

Subjectively, it also looks pretty darn good 🙂

Other info:

Maximum brightness – significant difference
original: 381 cd/m², replacement 474 cd/m²

Contrast ratio
original: 862:1, replacement: 891:1

On both, HCFR calculates an average gamma value of 2.18 without black point compensation and 2.21 with.

#supercurioBlog #calibration #display #color #development #measurements


In Album Display Measurements: my calibration algorithm on first batch Nexus vs refurbished replacement

Source post on Google+

A few days ago I sent back my Nexus 5, from the first batch shipped to France for a defect behind the glass lens

The replacement unit I received immediately seemed to have a better and brighter display, which is confirmed by the measurements graphs attached.

The replacement is brighter, with warmer white point, its RGB channels curves response are a lot closer across the board.
From comparing two phones, I can't tell if one is just better than the other or if Google improved the factory calibration process.

Neither display's white look like D65 daylight white compared to actual daylight or a reference CRT monitor (regardless of the sensor used).

Other info:

Maximum brightness – significant difference
original: 409 cd/m², replacement 510 cd/m²

Contrast ratio – about the same
original: 926:1, replacement: 952:1

Average gamma – interestingly about the same despite the difference in curves
original: 2.07, replacement: 2.08

Up next: results calibrated 😉

#supercurioBlog #calibration #display #color #measurements


In Album Display Measurements: first batch Nexus 5 vs refurbished replacement

Source post on Google+

This is a 3D visualization of Nexus 10 display color response compared to a reference Gamma 2.2, Rec.709 color space

Nexus 10 display gamut is small, so it doesn't cover the whole cube.
Due to the nature of its the blue primary, some colors would be outside the cube so I clipped them in this graph.

It's also the demo of a new tool that will help me greatly visualize measurement, calibration and correction data 🙂

#supercurioBlog #color #display #measurements #development


In Album 2015-05-16

Source post on Google+

As I'm thinking about +SpectraStudy #SensorMaster next feature instead of doing proper Saturday night activities, I got curious about how the spectrum of the displays right in front of me look

So there's one each for the Dell 2407 WFP, Galaxy S4, Nexus 5 and Nexus 10.

If the AMOLED and mobile LCDs spectrum are rather typical, the CCFL-backlight desktop monitor spectrum is unlike anything I've seen before.

Now I understand why no software nor sensor I used so far (based on the standard but old CIE 1931 2° observer model) has been capable of color-matching it with others, not even remotely.

This is great for me because that'll be the perfect benchmark for the physiologically relevance of the color matching function I'm integrating in my program.

#supercurioBlog #color #calibration #measurements #display #development


In Album Some white spectrum

Source post on Google+

Here's the full list of the measurements files I got during #MWC15 over 5 days, as I just finished sorting and checking them

.chc files contains data formatted for HCFR
.amf is for "all measurements file" (YAML dump)
.3dm is for "3D measurements" (YAML dump)
-Reference=5 are the readings I make at the end with a spectrophotometer to serve as correction matrix for the (faster) colorimeter measurements.

For each measurement run, that's 602 colorimeter readings and 5 spectrophotometer readings (saving XYZ values and spectral data for later usage)

That's 24 runs in total, each taking something approximately between 25 and 40 minutes depending on the setup time.

It encompass also 13 different devices in total:

– Samsung Galaxy S6 (2 units, multiple modes)
– HTC One M9 (2 units)
– Nokia N1
– Gionee Elife S7
– Asus Zenfone 2 720p
– Asus Zenfone 2 1080p
– Saygus v2 (prototype)
– Huawei Honor 6 Plus
– Huawei Ascend 7
– Lenovo VIBE Shot
– Nexus 6 (I didn't have this one yet)
– Meizu MX4 Ubuntu
– Lenovo A7000
– Panasonic CM1 (2 units)

Now that's a lot of high precision data to analyze 🙂

#supercurioBlog #MWC #display #measurements

Private Paste – Pastie
supercurio / François Simond’s MWC 2015 display measurements list. Samsung Galaxy S6, unit 1, 100% brightness, adaptive display, 2015-03-01_20-02-03-Grayscale=256-NearBlack=11-NearWhite=11-Components-Saturations=17-3D LUT Generator=216.amf. Samsung Galaxy S6, unit 1, 100% brightness, …

Source post on Google+

Today, day 3 at #MWC15 was great!

I progressed with the measurements TODO:
– Huawei Honor 6 Plus
– Huawei Mate 7
– Asus Zenfone 1080p standard and with white point tuned to warmer, after the 720p variant measured in different modes yesterday as well
– Saygus V2: I spent so much time talking there too with a very open-minded product manager who selected most of the device's components
– Lenovo VIBE Shot
– Nexus 6, because I didn't had it yet

What didn't work out:
– Sony who refused anything I needed on all their Z3 and Z3 compact running lollipop, the Z4 tablet and M4 Aqua (not a very promising device BTW), I even got annoyed a little bit.
– LG GFlex 2: all of them were running a custom build for MWC, preventing WiFi to work properly which I need for my portable lab.

Then I had the chance to meet by accident +Jeremy Meiss​, +Chainfire​ and a nice +Paranoid Android​ developer I'm very ashamed to have forgotten the name.

There's still a lot in the list, but it was a productive day.

#supercurioBlog #MWC #measurements #display #color


Source post on Google+