Plasma vs OLED - motion resolution

ArmitageShanks

Well-known Member
Sparkles might also be the result of a damaged/overheated/overclocked GPU. How hot does your phone get?

My biggest worry for current OLED tech is IR and screen burn. Try this in a dark room: display a bright pattern (e.g. the application icons on a black background) for a few seconds, and then display a medium/dark grey image (I normally just pull down the status bar). On my phone I can sometimes see dark shadows and outlines from the previous image. My SGS screen appears to be considerably more IR-prone than my plasma.
 

Scooby2000

Distinguished Member
They avoided using blue (and red and green) OLED completely. Each pixel consists of 4 white OLED subpixels. Three of them have color filter above (red, green and blue - just like LCD panels), fourth is transparent
Indeed they have though Samsung haven't, so wonder if they figured it out.
 

stucarblne

Well-known Member
VierraFan said:
They avoided using blue (and red and green) OLED completely. Each pixel consists of 4 white OLED subpixels. Three of them have color filter above (red, green and blue - just like LCD panels), fourth is transparent
Thanks.

Seems i will need to read up more on the tech. Wonder how long these new panels will last before a dip is obvious with brightness ?
 

Trollslayer

Distinguished Member
Good, this avoids one potential problem.
 

Scooby2000

Distinguished Member
Sparkles might also be the result of a damaged/overheated/overclocked GPU. How hot does your phone get?

My biggest worry for current OLED tech is IR and screen burn. Try this in a dark room: display a bright pattern (e.g. the application icons on a black background) for a few seconds, and then display a medium/dark grey image (I normally just pull down the status bar). On my phone I can sometimes see dark shadows and outlines from the previous image. My SGS screen appears to be considerably more IR-prone than my plasma.
How close are you looking? my S and now S2 are clear of IR.
 

Insanity202

Distinguished Member
Scooby2000 said:
How close are you looking? my S and now S2 are clear of IR.
Mine has it. Top of the screen where the battery icon, alarm etc are.
 

Scooby2000

Distinguished Member
Mine has it. Top of the screen where the battery icon, alarm etc are.
Never thought to look there as it rarely changes. I did notice my S1s screen was far from black in a dark room if UT had been on a while, S2s a bit better.
 

Insanity202

Distinguished Member
Scooby2000 said:
Never thought to look there as it rarely changes. I did notice my S1s screen was far from black in a dark room if UT had been on a while, S2s a bit better.
If you have the draw somthing app it shows off plenty on that.
 

stucarblne

Well-known Member
ArmitageShanks said:
Sparkles might also be the result of a damaged/overheated/overclocked GPU. How hot does your phone get?

My biggest worry for current OLED tech is IR and screen burn. Try this in a dark room: display a bright pattern (e.g. the application icons on a black background) for a few seconds, and then display a medium/dark grey image (I normally just pull down the status bar). On my phone I can sometimes see dark shadows and outlines from the previous image. My SGS screen appears to be considerably more IR-prone than my plasma.
Hi

I like the free ZD toolbox app it seems to be handy and accurate with a lot of features - easy on the RAM to which is a bonus.

Temp wise it doesn't seem to be getting above 24.5.C which seems about normal ?...

I know what you mean about the image retention i have seen it on many occasions
 

ArmitageShanks

Well-known Member
How close are you looking? my S and now S2 are clear of IR.
I usually can't see it in normal viewing conditions, but in a very dark room it can become noticeable, especially on a pure grey image (same as a plasma, come to think of it).

Mind you, these OLED screens are so bright (even at their lowest settings..which is what I keep my S on) that using it in a dark room is quite painful on the old retinas! :D It's not a retinal after-image I'm seeing here though...
 

VierraFan

Active Member
So, I tried to measure the black level

However, my instrument doesn't go below 0.01 Cd/m2, so I had to use alternative approach. I made a long exposure photo of the phone and my LCD monitor together and analyzed raw data from the camera to determine the black level (they are linear, unlike jpeg from the camera which is nonlinear and heavily processed hence not suitable for that). LCD monitor was set to lowest brightness. In that case it has white level 18 Cd/m2, contrast is 1:860 (determined with several measurements at higher brightness), so black level is 0.021 Cd/m2 (instrument shown 0.02) - similar to black level of UT30 plasma (just that white level is considerably lower because of significantly lower contrast)

First I set brightness of the phone to the maximum. In that case, black level is 0.0019 Cd/m2, while white level is 230 Cd/m2 for 100% white screen, or 290 Cd/m2 for 10% white and 90% black screen (obviously some power management used - like on plasma). Contrast ratio is 1:121.000 for pure white or 1:152.000 for 10% white screen.

By decreasing the brightness to 125 Cd/m2 (this was closest to standard 120 Cd/m2), black level slightly dropped, to 0.00166 Cd/m2. However, contrast ratio was almost halved

Quite decent for a mobile phone, although still short of marketed contrast ratio for even the cheapest LCD TV. :devil:

I attached a photo of first measurement below (it's intentionally slightly out of focus to avoid moire caused by interference between pixel structure of the screen and of the camera).

There are several things to notice. "Black" of LCD monitor has strong blue cast. Analyzing the raw revealed that its color temperature is more than 20.000 K, so I'm wandering why most reviews of LCD screens never revealed this big flaw of LCD screens - whether that data are omitted (in most reviews color temperature is shown from 20 to 100% APL) or are showing values around 9-10.000 K for 0% APL, and my monitor isn't the worst case, because it has CCFL backlight (LED televisions considerably worse) - in some reviews there is a sentence that shadows have slight blue cast and that's it ...

On the other side, "black" of OLED has red cast - color temperature is only about 1900 K. However, while blue tint of LCD is visible to eyes, this is too dark to perceive any color, at least for me. But very dark shadows (up to about 10% APL) also have red or yellow cast. Looks like this type of OLED screen has some problems with low levels of blue. Above 10% APL, color temperature of this screen is around 7500 K.

Another thing to notice is that this OLED has problems with uniformity of blacks, visible as dark dots or patches. However, I never noticed it except on totally black screen and wasn't sure that I see it even on black screen until I made this photo. On the other side, LCD panel itself has almost no uniformity problems with blacks, but however, has problems with non-uniformity of backlight, so it's certainly much worse

Black levels up to video level 19 are crushed - like on UT30 with default settings (however, there is no slider here to correct it)

Here is also a link to a page with similar measurements for some other mobile phones, two of them with OLED

Smartphone “Super” LCD-OLED Display Technology Shoot-Out

As a side note - my LCD monitor (Dell U2211H e-IPS) had maximum brightness 200 Cd/m2 when new, 1 year and 6 months ago. Now, it's only 145 Cd/m2. Contrast also dropped from 1:1200 to 1:860.
 

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ArmitageShanks

Well-known Member
Weird seeing those black spots on the OLED screen, they're too large to be individual pixels. I wonder what causes that? Are they always in the same place on the panel?
 

VierraFan

Active Member
Compared several photos and those dark spots are always at the same place. There are also some vertical bands (not as visible) - also always at the same place at the screen

It's because of nonuniformity of TFT panel driving those OLED pixels. Called "mura" in one OLED book.
Try googling "oled mura" and you will find many complains about this issue from PS VITA users that also has OLED screen
 
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Xenocyde

Novice Member
VierraFan, did you test the OLED screen on a Galaxy S? I have a Galaxy S and couldn't notice any black spots in dark room. I can sense some lines on greys, but I think that's the tactile matrix since it has a crosshatched look.

I think I also caught a glimpse of IR coming from the icons in the upper taskbar, but it cleared up pretty fast, in about 5 minutes. I accessed the photo gallery, slid through my photos in landscape mode, paying attention to the right side of the screen. I managed to make out a very faint icon, but I couldn't see any lines coming from the bar itself. After sliding to a fro for about 5 minutes, the icon was almost gone. It seems that this AMOLED screen is probably better than the average plasma screen in terms of IR. I'm still curious to see how the LG 55" OLED fairs in this respect.
 

VierraFan

Active Member
No, I have only this phone

Made another test clip to check can I actually see this mura issue on levels just slightly above black (level 16) in total dark, like camera. It turned out that it's mostly below my perception level. I think I can see some of these dark spots at levels from 20 to 24 which are still very dark. Above that, screen isn't very dark anymore but this issue isn't visible. I think that it wouldn't be a problem even on a TV

However, slight vertical bands/stripes are visible between levels about 24 and about 40, reminding me to similar issues with some plasma or LCD televisions ....

However, LG 55" TV will use different kind of TFT - Metal oxide. That one is said to have considerably better uniformity and is cheaper to produce because only 2 transistors per subpixel needed, while LTPS TFT used in Galaxy (and also in Samsung 55" TV) needs 4-6 to achieve acceptable uniformity.

About the black level, I found a video on Youtube, where Samsung is advertising contrast ratio of this display as 1:150.000. It seems that my measurement was spot on.




According to link I posted in previous post, Samsung was advertising contrast ratio 1:50.000 for Galaxy S. So it seems there was an improvement with S2 screen

Not sure about IR. I think that I noticed very slight evidence of it on dark grey in total dark, but way lower than on Panasonic UT30 plasma

Have yet to check 0.01 ms response time advertised in above video. Unfortunately, it seems that it's only partially true


EDIT: Samsung today announced some technical specifications about their TV. Contrast is declared to be the same as on this phone - 1:150.000, while response time is declared to be 1 ms
 
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VierraFan

Active Member
Yes, it is Samsung Galaxy S II, as I wrote in the very first post when I started this thread (and mentioned in several other posts I think). All experiments were on the display of this phone
 

Xenocyde

Novice Member
OK, I looked for the model only in the latest posts and couldn't find it.

Have you found any reviews about the newer Galaxy S3 AMOLED display? Would be interesting to test this new one.
 

VierraFan

Active Member
I didn't find reviews about it. What is known is that it has 1280x720 resolution, pentile pixel layout and the same 60 Hz refresh frequency

So back to response time OLED vs plasma stuff

When I got this phone, I wanted to know how the screen is refreshed and is its response time really almost instant as claimed, so I made several test clips.

It turned out that it is refreshed the same way as LCD, but response time is way better. I attached two photos illustrating this - one of LCD (in landscape orientation) and one of OLED (in portrait orientation)

Test clip consisted of alternated red and green frames at 30 fps. Both displays have refresh frequency 60 Hz, so each red and green frame was refreshed twice. Both screens are constantly refreshed/repainted from top to bottom, each refresh taking 1/60 s. Short exposure photo caught this process somewhere in the middle of painting the red frame over the green. Line "1" is currently addressed line, where voltages on subpixels are changed at the moment the photo was taken, according to change of color from green to red. After this, in case of LCD, liquid crystals start changing their state, so between the line "1" and "2", we see this transition. Distance between 1 and 2 minus duration of exposure (which was 1/500s) is proportional to response time. It is about 3/4 of height of the screen. Since refresh takes 1/60s, response time of the screen for this combination of colors is

(0.75 / 60 - 1 / 500) * 1000 = 10.5 ms

As we can see, for AMOLED, this transition is almost instant. Shortest exposure on my DSLR (used for this photo) is 1/4000s, and distance between line 1 and 2 is almost equal to exposure duration, so response time of the pixels is considerably shorter than 1/4000s. Value in range of 0.01 ms stated by Samsung for this display seems to be real

However, for their 55" TV, Samsung is stating 100x longer response time than for this phone - 1 ms. Also, one site measured "ghosting time" of several OLED displays and result was from 5 ms (15LG9500 - 15" OLED TV from LG, introduced about a year ago) to 17 ms (for display of this phone - Samsung Galaxy S II)

So I had to do some further tests ...
 

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Xenocyde

Novice Member
However, for their 55" TV, Samsung is stating 100x longer response time than for this phone - 1 ms. Also, one site measured "ghosting time" of several OLED displays and result was from 5 ms (15LG9500 - 15" OLED TV from LG, introduced about a year ago) to 17 ms (for display of this phone - Samsung Galaxy S II)
Maybe they used other techniques to test this. However, your technique is quite consistent and the 0.01 ms response time looks to be accurate. That 1 ms on the 55" OLED is not bad either, it's still better than the 2 ms on current 24" gaming LCDs. Hopefully they didn't introduce any reverse ghosting problems like we see in many 2 ms LCDs.

My understanding is that current LCDs are measuring grey to grey response time, not black to black or white to white. Is that 1 ms for OLEDs g2g or b2b/w2w?
 

VierraFan

Active Member
There are different methods to measure response time of the screen. For LCD screens, most used is g2g. It is calculated as average of times needed to change between different video levels, usualy 9x9 combinations. For typical IPS screen with overdrive, it is 7-8 ms. Response time in above experiment is showing the longest of two combination, and it is changing the level of green from maximum to minimum. Checking the values of red channel in the photo of LCD screen will show that the time needed for red to change from minimum to maximum is about the half of that. Average of those two is close to g2g for IPS panel

Mentioned site (I don't like to reference the names, but in this case it is digitalversus.com) is measuring "ghosting time" by scrolling the test image (several icons of different shape and colors) on the screen and measuring the time needed for image from previous frame to completely disappear with high speed camera.

New 'Ghosting Time' Test for TVs, Monitors and More

So actually it is also showing the worst of all response times.

To give some hints why they measured 17 ms instead something like 0.01 ms for this OLED display, I attached another pair of photos, where instead of red and green frames, red letter "A" was alternating with green "B" on black background. First photo for LCD second for OLED.
 

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Xenocyde

Novice Member
Hmm, that Digital Versus test is a bit old. They tested a GT20 plasma and it got 8ms, not the fastest screen since the OLED got 5 ms. I though plasmas were capable of under 1 ms response time.

These French guys from Digital Versus (Les Numeriques) are quite biased sometimes. Take a look at their Panasonic Viera TX-P50VT50 review.

Their black level measurement is too high, contrast is too low, and viewing angles are comparable to a PVA LCD, although they say that viewing angles are nearly perfect... what the hell were they thinking? I wouldn't trust these guys too much after seeing this review.
 
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VierraFan

Active Member
My impression is that some sites are indeed biased or sponsored, so I wouldn't be surprised if this one is among them, that's why I said I don't like to make any references, but I made an exception because, as far as I know, it is the only one that has some measurements of OLED screens at the moment

In case of VT50 black level, they admitted that they suspect their instrument being inaccurate. However, I'm frequently surprised with amateur approach from someone who supposed to be a professional, while I have to cope with cheap equipment I have when doing these experiments

As about plasma response time, it's a bit of nonsense to put LCD and PDP displays in the same table, because they are producing picture in a very different way, as I demonstrated several months ago. And yes, response of plasma is indeed very fast, but unfortunately, decay of green and red phosphor isn't that fast (while of blue is instant), that's why we have yellow trails

From the last pair of photos I attached, it is evident that response of OLED is also different from both LCD and PDP, so although response time is very short, their measurement of ghosting time for this screen (17 ms) is actually correct - unfortunately
 

Xenocyde

Novice Member
Well, since OLEDs are in their infancy and cost a small fortune for now, we can only hope response time and whatever shortcomings we may find in the latest generation of OLEDs from LG and Samsung would get improved over time, along with a price reduction. Any info on how Crystal LEDs from Sony perform?
 

Nicholars

Banned
To be honest I would rather sacrifice some motion resolution and not have any flickering eg. panasonic plasma flicker.....

Flickering to me is unbearable whereas on the really good LED TV's such as the top of the range Sony's the motion looks completely fine to me anyway.... On my Sony HX723 the motion is pretty much the best I have seen on any TV... even I prefer it to the Samsung plasma I had before it.... The motion on Panasonics is sharper and generally much better but the flicker completely ruins it for me...

Most other LED such as LG or even samsung the motion looks dodgy and has the fake 100hz look to it but Sony have got it just right IMO. Not perfect but nothing that you can really notice unless you are sat 1 foot infront of the screen looking for errors....

I would prefer anything over the flickering you get on panasonic plasmas frankly.

Would be nice to see perfect motion resolution as well as perfect blacks but hey you can't have it all as people on this forum have probably noticed there is always SOEMTHING that is wrong with every TV lol.
 
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