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

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I started implementing an Android system driver using the GPU for color correction and calibration

I already hit some limitations here and there (being well known by game developers) but am confident in the possibility to find solutions to get satisfying performance and results on all OpenGL ES 3.0 devices and most GL ES 2.0 ones as well.

And here's something to show you!
In my last post, I mentioned how exciting it was to not be limited to 8-bit per channel precision, which is a tough compromise when correcting displays because it means you introduce banding.
Yesterday's post: https://plus.google.com/+supercurioFrancoisSimond/posts/Dv7JzLAP5ev

In these graphs, there's a Nexus 5 running the driver in development which naively divides RGB values per 10 which makes the output much darker.
At 100% brightness: it hits 3 cd/m², for a contrast ratio as low as 10:1.

See for yourself the result of changing colors on 8-bit, vs what can be done by creating those intermediary tones that the display hardware, a 8-bit panel cannot produce.

Image 1 and 3: 8-bit
Image 2 and 4: same 8-bit, same content but but simulating the intermediary colors using GPU post-processing.

I didn't expect such extraordinary results, but it's real 🙂

#supercurioBlog #calibration #display #color #development

   

In Album Better than 8-bit per channel precision

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Excellent question from +Aden J Purcell:

Apparently the display on the G4 follows the DCI color space instead of sRGB. Do you know if this is a good thing? I thought movies were mastered in sRGB, not DCI? And even if LG has accurately calibrated the G4 to DCI, could they have messed up the gamma? Or is a 2.2 gamma part of DCI meaning LG can't mess with it otherwise they can't market their device as DCI compliant?

Like +Samsung Mobile has done before, marketing their Super AMOLED devices as color accurate according to the Adobe RGB standard to appeal to photographers, +LG Electronics described the LG G4 display as following another standard they call "DCI"

First of all, DCI acronym stands for "Digital Cinema Initiatives, LLC" and not the name of a color standard.
Assuming they are talking about DCI-P3 color gamut, it's the gamut part of one of the color encoding formats for professional cinema projection.

DCI-P3
– white point coordinates x: 0. 314, y: 0.351 vs sRGB x:0.3127 y: 0.3290
– gamma 2.6 vs sRGB around 2.2 average
– pretty wide gamut, color primaries color hues not being the same as sRGB: green has less yellow, red has less orange,

A comparison of sRGB and DCI-P3 color gamuts by +Jeff Yurek's blog:
https://dotcolordotcom.files.wordpress.com/2012/12/pantone_2013_dot_color.png
Additionally, the white point is not even the same.

Today, Android applications lack color management abilities which would allow to convert one color encoding to another and display content as intended on various displays seamlessly.

+LG Electronics throws in the "DCI" name to impress reporters and customers with the intent to convince them of the benefits in color accuracy and true-to-life color reproduction of their new display.

However, when checking what they're mentioning stands for, it is clear that displaying today's content, which color are encoded using sRGB (Rec.709 gamut and around 2.2 gamma) on a "DCI-P3" display (wide gamut and gamma 2.6) would lead to particularly inaccurate color rendering.
Colors would not be rendered with the right hue, look too intense (over-saturated look), and annoyingly too dark due to the gamma 2.6, which increases saturation even more.

In conclusion, +LG Electronics is proud of their new wide-gamut display but please don't be fooled by the marketing mumbo-jumbo employed.
It doesn't correspond to any professional standard or any standard altogether, it will distort colors instead of rendering them faithfully, and this is mostly a response to Samsung, just as bogus Adobe RGB accuracy claims.

Source: DCI-P3:
http://www.hp.com/united-states/campaigns/workstations/pdfs/lp2480zx-dci–p3-emulation.pdf

#supercurioBlog #LG #critic #marketing #color #display



www.hp.com/united-states/campaigns/workstations/pdfs/lp2480zx-dci–p3-emulation.pdf

Source post on Google+

I worked hard on the +SpectraStudy Display Color Simulator today and have pretty great results emulating the color response of a Nexus 10 in this example

This is still work in progress and unfinished as I know not everything is implemented yet in terms of color spaces regarding alternative color matching functions.

But already, in this sample using CIE 1931 2° modified by Judd & Vos color matching function, from spectrophotometer readings looks really close to the real thing.
This is when comparing, in person the Nexus 10 to the simulated image displayed on a calibrated display.

More on that later!

#supercurioBlog #calibration #display #color #development

   

In Album 2015-03-29

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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

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Colorimeter measurements corrected from spectral readings

Late yesterday night, I completed the math and code to adjust my display high precision colorimeter measurements with spectral readings taken with a spectrophotometer.

During #MWC15 , I was going booth to booth with both a X-Rite I1 Display Pro colorimeter, that's particularly quick and a EFI-ES1000 spectrophotometer (same as a X-Rite i1 Pro), connected alternatively to the tablet running my software.

The spectrophotometer is about 3 times slower, but has the merit to see the light wavelengths intensities while the colorimeter uses some kind of RGB sensor that's able to tell the real colors only if their spectral characteristics match what it has been optimized for.

The correction logic was not implemented until now, so here are graphs from a +HTC One M9 unit, before and after correction.

Not only the spectrophotometer doesn't see the same thing, but these measurement confirm why you've heard reviewers mentioning a ''green tint" on the M9.
It's indeed here, and our eyes are very sensitive to an excess of green. We tend to be less bothered by wrong amounts of red and blue however. The M9 display also has too much blue and not enough red.

#progress #supercurioBlog #color #display #calibration #development

     

In Album Have correction from spectral readings now

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 🙂

http://pastie.org/pastes/10008275/text?key=yp0tsbbxyps64eqsqeavsq

#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, …

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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+