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Tab S 8.4 Screen homogeneity issues

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By ukael, Member on 24th July 2014, 01:54 PM
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29th December 2014, 03:51 AM |#51  
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Quote:
Originally Posted by DUHAsianSKILLZ

Where are you guys getting these screen issues? Like which shop and country/state.

Mine from Malaysia Samsung Store.
 
 
29th December 2014, 04:09 AM |#52  
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Quote:
Originally Posted by Andrewtst

Mine from Malaysia Samsung Store.

Wow inside the Samsung store? Dang. I got mine from Walmart a few weeks after launched. No issues so far. My country is USA.
29th December 2014, 08:53 AM |#53  
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Quote:
Originally Posted by DUHAsianSKILLZ

Where are you guys getting these screen issues? Like which shop and country/state.

Mine was in France, FNAC store
29th December 2014, 10:59 AM |#54  
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Originally Posted by DUHAsianSKILLZ

Wow inside the Samsung store? Dang. I got mine from Walmart a few weeks after launched. No issues so far. My country is USA.

That unit is probably lemon set. Lucky now my unit is in great condition.
6th January 2015, 04:31 AM |#55  
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Mine's is a 8.4 from staple Canada and I can notice a small purple shift in the dark grey tone on the bottom of the screen when the room is dark. When the black is really black I have no issues. I used SwiftKey with material dark theme an the issue is there, again, only when the room is dark, tab luminosity low and the color are plain, not noticeable on photos and videos.
29th January 2015, 08:37 PM |#56  
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So I'm not the only one..
Hi there!

Thank you, ukael, for starting this thread. I bought this tablet mainly because I like to read in the bed and the no-lightbleed-possible OLED display was the single most important thing that made me go for it. So, yes, I was also a bit disappointed when I noticed that the text (white on black background) has kind of blue / red tint to it in one corner, and green-ish in the other.

I'm still wondering about whether I should get a replacement, but since I see that many others here report the same issue with their S 8.4, this is probably due to the limits of the manufacturing technology used and the new unit could possibly be even worse. And considering that the world is not overflowing with OLED display wielding devices yet, it is probably not an easy task to manufacture one without any flaw, so I can't really hold any grudge against Samsung -- it is still an amazing screen in many ways.

That said, it _is_ kind of annoying at times and I'm still thinking whether this could be corrected in software -- there are probably some differences between any two devices, but the main part of this problem is that the screen is too bright in the top-left corner and / or too dark in the bottom-right one* and each channel behaves differently (see attached pictures**). It could be possible to simply apply gradual gamma correction for each channel so that the dark areas get a "boost" and show up brighter as they should be.

There are already programs doing some color filtering magic, like CF.lumen, but I'm worried whether it would be possible to apply a correction in the form of a gradient -- uniform filtering of one color is one thing, but applying a gamma correction and deciding for each pixel what is the right value could be too GPU-intensive to make it a viable option. But I'm not an expert, so I keep wondering... Any ideas in this respect, anyone?

--
* My guess is that the display data connections are in the top-left corner (portrait mode) and the signal voltage simply drops too low before it reaches the bottom-right area. Since LEDs have a non-linear output dependence on the applied voltage, getting a precise light output level when it is nearly switched off is very difficult -- it reacts "wildly" to even slightest change in voltage, so it is not much of a surprise that the unevenness becomes worst at the lowest brightness setting / when using dark colors..

** First three photos are displaying R: 10, G: 0, B: 0 etc. at maximum brightness; the last one is G: 10, B: 20 or the other way around, I kind of forgot. All are using the same exposure 5 seconds and ISO 400. (The bright points are in fact white (menu buttons in ArtFlow used for testing), the green tint is likely just some weird effect of the lens in my camera.) The blue channel is obviously not affected nearly as much as the green and red channels and that's where all the color differences come from..
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29th January 2015, 08:41 PM |#57  
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18th February 2015, 05:15 PM |#58  
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I had my 10.5 replaced this week partly because of a yellow tint on pure white screens but the replacement is just the same
On pure white screens i find that, in landscape mode, about 75% of the middle horizontal has a slight yellow cast and if i tilt the top or bottom by an inch it makes that cast disappear by moving it mostly off to the top or bottom. I can't quite work out if i'm just being picky and can't actually tell what white should look like. I know i prefer a colder tone to a warm one on my TV and monitors as they look far more accurate to me so maybe my vision of a perfect white is moving into the blue and is just different from Samsungs? My current Tab tested with the "R0 G10 B20" dark image shows the absolute mildest mura effect at lowest brightness while the previous one was a bit more prominent. Also the yellow cast is the same in greyscale ultra power-saving mode. I think that's something people could check to remove colour calibration issues.
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