10-bit color on OSX El Captain

The first thing.. okay the second thing I noticed when looking at a couple Retina iMac was the large amount of banding in gradients.
Like this one:
http://dl.project-voodoo.org/screen-tests/gradient-2560×1600.png or a dithered version

It seems that Apple was applying a correction profile on only 8-bit – and quite a bit of it, which on this very large and sharp panel created simply banding galore.

10-bit, even for apps that support only 8-bit per channel (24-bit colors) should at least fix the calibration banding issue, if all is as it should be.

#supercurioBlog #color #calibration #banding

Originally shared by +PetaPixel

OS X El Capitan Quietly Unlocked 10-Bit Color in iMacs and Mac Pros

OS X El Capitan Quietly Unlocked 10-Bit Color in iMacs and Mac Pros
OS X El Capitan added some major features to the operating system when the update was released at the end of September 2015, but it appears that there was

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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 https://plus.google.com/+supercurioFrancoisSimond/posts/cgKUgJEPTtc

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

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There's a new revision of the popular X-Rite i1 Display Pro colorimeter out here, and the latest ArgyllCMS release is not able to drive this sensor fully yet

+Vincent Sergère is a proud owner of one and can't use it quite yet for what it's intended for now.

Hoping this message will help ArgyllCMS's author!

#supercurioBlog #development #color #calibration

[argyllcms] Error with new i1 Display Pro revision – argyllcms – FreeLists
[argyllcms] Error with new i1 Display Pro revision. From: François Simond ; To: argyllcms@xxxxxxxxxxxxx; Date: Fri, 9 Oct 2015 02:29:27 +0200. Hi Graeme and the list! I’m assisting a friend with his brand new X-Rite i1 DisplayPro, which has a new revision and firmware.

Source post on Google+

Nexus 6P AMOLED panel info

"SW: It has a Samsung WQHD AMOLED panel. We have spent a lot of time tuning the white-point and color gamut for these panels – hope you will enjoy the accuracy of the display."

"Yep, confirmed: Nexus 6P has the latest generation panels from Samsung. One of things we deeply care for is the quality and accuracy of the display through which all of us connect with the stuff we care about. We created a very tight spec (white-point temperature, delta-E variance, color-space accuracy, etc) for the 6P WQHD AMOLED panel, so it was important that we use the most cutting edge panel technology available."

That sounds good, and especially after +Dave Burke​​​​​​​​​​ claimed on stage that the display was "very vibrant", this promise of color accuracy will need independent verification 😉

Note that this answer doesn't specify to which color space or white point they decided to conform.
This display will show near exclusively content encoded to sRGB standard (which specifies the white point and RGB primaries, gamut and electronic-optical transfer function – aka EOTF aka gamma curves).
In case the display colorspace they chose is wide gamut, any color accuracy claim is automatically moot given the fact Android doesn't support color any management at the moment.

There are various ways to calibrate a wide gamut AMOLED to conform to sRGB specifications tho: using the panel's factory calibration in conjunction with either:
– the panel's color tuning
– Qualcomm Mobile Display Controller image processing, with basic colorspace conversion or 3D LUT
– the GPU (which taxes some GPU power however)

#supercurioBlog #display #color #calibration #Nexus

Hi, I’m Hiroshi Lockheimer, here at Google with the team that build Nexus 5X & 6P…Ask Us Anything! • /r/IAmA
Yep, confirmed: Nexus 6P has the latest generation panels from Samsung. One of things we deeply care for is the quality and accuracy of the…

Source post on Google+

Okay so calibrating the +Sony Smartwatch 3 display colors is gonna be tricky given how the measurements come out

Calculated from data: contrast ratio of 8:1.. yeah, nope that's not right ^^

However you can see quickly why colors on this display look so strange: the blue channel is way off and clips at IRE 82.
It might be a deliberate attempt of the people who profiled the panel to make it appear colder blue than the white point really has.
As you can see on the RGB Levels graph, there is tha much deviation between channels. If you saw the watch display in real life: you probably knew already.

I don't know yet what is it that makes darker values brighter than they should: it might be a content adaptive brightness algorithm tuned for readability.
As seen on the CIE Diagram there might be some more color processing going on as well.

The small size of the display is compared to the size of the X-Rite i1 Display Pro is not making things easy, I'll try tuning my patterns and using the i1 Pro instead.

Well, you gotta start somewhere right?

#supercurioBlog #calibration #color #display


In Album First attempt at measuring Sony Smartwatch 3 display

Source post on Google+

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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Some facts after a quick analysis of both +HTC #ONEm9 and +LG Mobile Global #LGG4 produced DNG

– Both lack flat-field correction
– Both provide incomplete matrix-only color profiling: no DCP
– Neither use compression
– HTC One M9 DNG is 10 bit stored in 16bit uncompressed data: 39MB per 20 Mpixel image.
– LG G4 DNG is 10 bit stored uncompressed, 20MB per 16 Mpixel image
– Both have non-optimal noise profiling settings: HTC One M9 set noise reduction too high and LG G4 lacks noise profiling entierly.

Notes on flat-field correction:
Mobile camera modules require such correction to correct both vignetting and color cast (like pink spot / greenish or blueish corners).
HTC One M9 requires less correction than the LG G4.
It is only possible to compensate for light fall-off, in RAW image editors, not color cast.
As a result, the color cast in corners is essentially non-fixable.

Attached: the #LGG4 DNG sample provided by +Colby Brown rendered in Lightroom with only modification an increased contrast and exposure slightly, to make both vignetting and color cast more obvious.

The least I can say is that there's room for improvement, both DNG implementation being non-optimized and incomplete.

#supercurioBlog #LG #DNG #color #camera #calibration


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

Source post on Google+