Today, #MWC14 last log:

In terms of smartphone displays I measured:
– Gionee's Elife S5.5
Quite incredible super thin device from a manufacturer you might have never heard of, but who realized something that forces respect.
At 5.5mm, it provides the same battery capacity as the 8.59mm Nexus 5.
S5.5 display is a Super AMOLED 1080p that looked similar if not identical to the Galaxy S4 one.
Camera sensors and app are quite convincing (5Mp front) with plenty of cool & advanced features that are actually usable.
I also grabbed a Voodoo Report from it as I'm curious about it's Octacore Mediatek SoC.

– A Firefox OS Huawei smartphone, the Y300.
In the middle of other new Firefox OS devices, I picked this one as its display is IPS and for the price I must say it doesn't look bad at all. Incredibly better than its siblings using TN displays for sure.

– Nokia Lumia 1520
I'm sure you know about this one already.
Lumia's display is quite impressive in person so I had to take readings about this.
For the record, I had to modify my measurement HTML5 app because IE browser was caching AJAX requests more than anticipated ^^.
Cache-control headers did the trick.

– Nokia Lumia Icon
Probably the most interesting and usable Lumia smartphone at the moment. It's the same hardware platform as the 1520: S800 / 1080p display but using a 5" Super AMOLED instead of 6" IPS.

– Xiaomi Mi3
Qualcomm's booth had a pretty amazing collection of Snapdragon-equipped device.
Because, you know.. they're very much in most smartphones those days 😀
I had little time left in the end but still measured this one as it's not so easy to get a hold of it, and also the display and it's factory calibration were pretty convincing and I look forward processing the measurements to confirm some very quick first impressions.

Today was also the opportunity to spend more time with +Richard Lai, who demonstrated extraordinary group hug capabilities then accompanied me to +Ubuntu booth.

Good folks at Canonical appreciated this original usage of Ubuntu touch.
− the Nexus 7 in these pics, driving a colorimeter and a spectrophotometer using my app runs under the ARM & touch oriented port of this Linux distribution.
I tried to made a demo for them and despite an alpha development stage, if everything worked perfectly during the show it didn't for a demo to them.
Oh well, typical 😀

Today was also the opportunity to talk with +Qualcomm engineers. I spent hours in total the last 3 days talking with a senior product manager and a software engineer specialized in hardware video processing and scaling algorithm.
Both were as knowledgeable as it gets and knew everything about display calibration as well, which was refreshing as not common.

Qualcomm will take a closer look at my Nexus 7 display calibration development drivers & algorithm, they were surprised I was able to do what I'm working on already without their help, and recognized it's a valuable usage of their silicon 😉

At the end of the day I had the privilege to meet, talk and shake hands with +Mark Shuttleworth who actually knows a lot as well about display calibration and why mobile OS should be capable in this area as well.
His mention of color accuracy on Ubuntu Edge introduction video was no accident.

In the next days I'll process the spectral and reference color data from the spectro sensor to get correct the colorimeter readings from all those displays and share that with you.

Already I must say see a positive trend since last year.
Higher resolution displays yes but also more capable of reproducing the full color gamut − sometimes too much.
Most manufacturers seem to buy factory calibrated panels but some still downgrade them with uninspired processing.
Overall it's pretty positive and this was an awesome, far too short MWC

#supercurioBlog #display #measurements #MWC


In Album 2014-02-27

Source post on Google+

Measuring +Sony Xperia Tablet Z2 in a private media booth

I made sure taking a good sample device – that's still a prototype as some had completely yellow displays 😉
The one I have here should be most representative of the final product hopefully.

I'm curious about this tablet because the gamut seem wide as well, however there's something going on with the saturation I don't like too much.
Well, measurements will tell 🙂

Also I get to measure 2 more Z2.

#supercurioBlog #display #measurements #MWC


Source post on Google+

Early measurements results of a +Sony Xperia Z2, captured from +Erica Griffin computer screen as she couldn't wait to see the results

I'm impressed by the capabilities of this device so far.
Gamut is large, comparable to Super AMOLED displays.
On the Z2 devices demonstrated in Barcelona, there's no chroma saturation boost added. If color seem plenty intense they don't look too over-saturated like we've seen often on Samsung wide gamut panels.

A bit later I'll publish the full measurements corrected based on a reference spectrophotometer, for precise color temperature and gamut evaluations.
Also, planned : wavelength spectrum to look even more in depth into this new +Sony backlight technology!

#supercurioBlog #display #measurements #MWC


In Album 2/24/14

Source post on Google+

Currently measuring +Sony Xperia Z2 display :-)

You can see in this picture my exclusive analysis rig.

There's some dynamic contrast going on but besides that I can tell you already that Sony stepped up big time in panel quality compared to the Z, Z1 but also Z1 compact and Z Ultra.

#supercurioBlog #display #color #measurements


Source post on Google+

Yesterday I finally wrote my first display auto-calibration algorithm

Results are good 🙂
Also the approach is completely different from everything I saw so far.

Attached: D65 calibration on Nexus 7 (2013): very first results

I take all the measurements I need first and then everything can be done with calculations.
Usually auto calibration algorithms measure various kind of color patches that I can't justify, then try to improve their vastly interpolated early results by several optimization pass.
Not sure why they do that as it seems inefficient. Maybe those algorithms were designed with different goals in mind than mine.
Like if you're not sure of what the hardware will do with your profile, so you load it, retry, again and again.
But it means you're not measuring correctly to begin with or working with inconsistent and unpredictable hardware.

A huge benefit of my approach seems to be the accuracy first, and also you can tune the algorithm parameters all you want without taking any new measurement (which takes a vast amount of time).

Today I'm adding black point compensation strategies in it in order to provide a smooth gradation near black instead of clipping at rgb (10, 10, 15) on Nexus 7 (2013) when targeting a Gamma 2.2 response curve with pure black output.

And I'm having a lot of fun doing this!

I was really not sure I would be able to make this auto calibration thing, thinking I was too limited in my maths skills.
But it seems to be no issue even if it took quite some time to turn to code the theoretical concept I had in mind.

Back to code 🙂

#supercurioBlog #calibration #display #color #development


In Album Very first auto calibration algorithm results

Source post on Google+

Alright I almost completed a brand new automated universal display measurement engine :)

The key here is that it's capable of measuring pretty much any kind of display: smartphone, tablet (any OS), TV, computer..
It also uses several techniques to give accurate results even on display implementing funky dynamic contrast, content adaptive backlight control or other similar effects.

During the process I learned a ton about color theory, maths, algorithms, colorspace conversion and representations.

..Which now gives me ideas on how to write my own automatic and high precision calibration engine!
Later maybe, but it's stuff I'm dreaming of since years actually.

Just letting you now that despite I didn't released new snapshots of the Android app, there's progress 🙂

#supercurioBlog #display #measurements #color

Source post on Google+

Dear next person telling me "Movie Mode" on Samsung smartphones or tablets is color-accurate:

Please check your eye sight with a professional, and don't wait!

Here's the funky color response of Samsung Galaxy S 4 I9500 in Movie Mode.

#supercurioBlog #color #display #measurements


Source post on Google+

Oh yeah, a win here!

Latest 2 or..3 days? and a bit more, I lost track of time I worked on something new, that among other things allows full-resolution measurements.

I never saw that before but I really wanted that for years so.. I did it 🙂
256 values per graph for grayscale.. can't do more accurate on a 24bit display!

This is a very good step towards a full calibration suite for mobile. I'll explain more about it later.

#supercurioBlog #display #measurements #color #development


In Album First full resolution measurements

Source post on Google+

In their press release, +LG Mobile states, quoting:

accurate colors and clear images without any distortion

Here are measurements of Korean G2 F-320K display that +Erica Griffin has for review.
What I see in those measurement is a different story that what the manufacturer states.

Some diagram interpretation:

CIE gamut and saturation view:
First thing, gamut is a bit larger than sRGB standard with green reaching further, on y axis mostly which means maximum green will be a tad more intense, it's not too bad and as-is will probably just look nice.
However if you look at the saturation, something is happening here:

Green and Blue channels mostly are extremely compressed.
As a result, green at 75% saturation is above sRGB standard coordinates, blue at 75% saturation is not much different from 100% blue.
Cyan gets the same treatment as green and blue.
Red saturation is less compressed, LG was more careful here as it's easy to make people's face look red so people identify this as over-saturated colors immediately.

Gamma and Luminance curves:
Gamma constantly above 2.2 which is the usual calibration target, and about average of sRGB standard.
Average gamma value ends up at 2.46, with an actual contrast ratio of 1097:1 (dynamic contrast neutered)
What does that means? You can see the result in Luminance diagram: the image looks artificially too dark.
It's not that bad when you're in dark viewing conditions, but kinda extreme for a smartphone you will use also in bright viewing conditions: making some things hard to see.
Making the image darker also automatically increase color saturation.

White point temperature:
It seems LG chose D75 illuminant here as target (7500K) even if a spectro would be required to give a perfectly accurate reading.

My conclusion here is clear:
LG say what people and the press want to hear: "accurate colors" but does something else.
They're also surfing on the urban legend stating that IPS displays have accurate colors, bashing their Samsung in the process (which is well deserved on some aspects). Yet aren't they're trying to mimic them at the same time?

Both selective color saturation increase and gamma and darker response curve are here to make the image pop regardless of color accuracy.
Those two elements seem like an attempt to make this IPS display look like an AMOLED panel, or at least a "vibrant display".

It might look good to some buyers but please, LG, don't state you're calibrating your display for accurate colors […] without distortion while you're applying processing with a very specific agenda, that has nothing to do with color accuracy.

Will the non-Korean G2 have displays that are targeting color accuracy?
We'll know that in a couple days.

#supercurioBlog #display #measurements #color


In Album LG G2 display measurements (Korean F-320K)

Source post on Google+

Calibrating my Nexus 7 (2013) to standard sRGB 6500K

First attempt & beta profile

I'm currently writing a solution that will, as absolute first on market to calibrate your tablet using a colorimeter or spectrophotometer.
No erratic slider tuning here, this is the real deal with 256 values per channel.

With this solution, Nexus 7 (2013) will becomes a tool of choice for professional photographers and graphic creators to showcase their work on the go, thanks to a display that might rival their desktop monitor in terms of color reproduction accuracy.
As there's always variation between devices in production, the key is to allow the user to calibrate his device on his own.
(It requires having access to a sensor)

So far, color calibration has not been a priority of +Android Developers or manufacturers:
Most devices are released without any calibration effort, and Android OS doesn't provide any solution to the situation either, being incompatible with ICC profiles.

I'm very early in the development of this solution as I got my tablet yesterday, but in the meantime, here's some measurements with a profile targeting D65, the standard sRGB white point.

+Romain Guy there's a few photographers in your dev teams. Do you think anyone would be interested integrating such feature in Android?

– Contrast ratio is 1103:1
– This is my very first attempt, I'm sure even better results can be obtained.

#supercurioBlog #calibration #display #color #development


In Album Nexus 7 (2013) first D65 display profile

Source post on Google+