Hi Dovez, I have tried the stuffs again just now. From the limited time I have tested, there didn't seem to have an apparent difference between a completely blank white screen versus a screen with graphics, texts, etc. in terms of comfortability.
I have also tried laying a semi-transparent plastic bag in front of the screen, the light intensity was dropped for sure, but it didn't seem to make the light more comfortable to look at.
HOWEVER, when I set the screen to a non-native resolution (from 1366x768 to 1152x720), the screen does seem to look a little bit more comfortable! This is very strange!
Thanks for trying the tests. The results seem conflicting and perhaps they are. I am completely sure it’s light that is causing the problem, or to be more precise – one or more of its properties. From what I know so far, light has these properties:
With the bag test we can exclude: light patterns (all of them should have been diffused into nothingness), polarization (the light should have been diffused into all directions), brightness level (brightness obviously made no difference).
The non-native resolution test excludes: spectrum, brightness level and polarization (the resolution brought relief without all of these properties of light having changed, so they can be excluded).
The only thing we cannot exclude completely from these two tests is flicker. The symptoms are identical to flicker symptoms.
It is some kind of not obvious flicker happening at the subpixel level even with pixels displaying white, which should normally mean that they are as transparent as they can be, displaying nothing at all, but the tests indicate that this could possibly be not so. A change in resolution seems to cause some information that is sent to the display to get lost or deformed, possibly the flicker information. The fuzzy image that a non-native screen resolution brings is responsible for some remaining discomfort with the screen.
This is the only explanation I can make with this data. Perhaps it is a chaotic subpixel flicker like the snowing on TVs and that’s why it can’t be detected with flicker detection methods, since all of the subpixels involved are not turning on and off at the same time. We can exclude the backlight flickering, since the change in resolution brings relief and is hasn’t influenced the LED backlight in any way.
Thank you for your analysis Dovez!
After resting for the night, I am trying the things again today. It seems the most comfortable setting for my MacBook Air is to use the 1152x720 (non-native) resolution and full brightness. It's still making my eyes uncomfortable, but I would say it's about 70% better.
I agree your say that something is flickering, my discomfort feeling certainly matches that, it's probably just we don't have a reliable method in detecting it.
It could be the subpixels flickering like you said, though I don't really understand why they has to flicker when displaying a blank white screen. It's even more weird to find that a blank white screen in a non-native resolution is more comfortable than a blank white screen in native resolution!
The difference is perhaps it's the OS handling the subpixels directly when the screen is at native resolution (and maybe there's a bug somewhere?), while it's the GPU that handles the subpixels in a more traditional way when the screen is at a non-native resolution.
I also wonder if the screen can display all the color it needs. Maybe it has to flash the pixel to get some of the shades it needs. (e.g. flash a green pixel when displaying dark green)
Just my guesses.
I found a very interesting link about white pixels flickering.
Quotes: " I am experiencing something like a snow effect", "The problem is not visible on screenshots or videos"
It sounds like the same problem that I theorised about, just exagerated to the point at which the white pixels flickering are visible. And it is not visible on video, which probably means cameras can't detect the snowing flicker effect. This case isn't evidence that the same is happaning here, but it seems very similar and software related.
After a few tries with different screens, I came to the conclusion that my problem laid with the latency between images.
I realize I might be sensitive to a latency <5ms, which I can't bear.
For example this screen is fine with me:
It has LED backlight, but 5ms of latency.
On the other end, this screen quickly gave me eye strain:
(sorry, this one is in French)
Does anyone know what's the latency on Apple's laptop screens? Or even on the iMac?
Both of those screens use TN panels, which have the best pixel response time of all (and worst everything else), the NEC you said has 5ms prt, the iiyama I read has 2ms. These are all specs from the company of course, and usually mean grey to grey response, actual response time is somewhat higher, but still small. Apple displays use IPS panels, which have a higher (slower) response time than the ones you listed. Usually over 10ms. My advice is you shouldn't be looking at the response time as the source of your problems.
But the fact you had different experiences with two at first look very similar monitors is interesting. Can you perform the flicker test on the NEC?
there are interesting thing with resolutions with rMPB:
System settings allows you to select 5 screen sizes – 1024 x 640, 1280 x 800, 1440 x 900(default one), 1680 x 1050, 1920 x 1200
Once you select one, it retinezes it (x2 on both dimensions) so you get 2048×1280, 2560×1600, 2880×1800, 3360×2100, 3840×2400
then it upscales (in case of first two) ot downscales(in case of last two) the image to fit 2880×1800.
So blur (in case of upscale) and lost pixels (after downscale) are not that noticable when pixels are small (220 pixel per inch).
this combined with internal LCD dither can lead to subtle flickering/subpixel drizzling of image on some resolutions.
Flicker test? Do you have a link to it?
I'm currently using the NEC display right now, I did return the iiyama one, so I won't be able to run any test on the iiyama.
Also, I used this screen since 2009-2010 :
and it worked fine for me as well. By looking at its specs, I realized the major difference between it and the iiyama was the latency, so I decided to try the NEC one, and it worked just fine (I needed about one or two days to get used to it.)
The major difference between the HP and the iiyama is that the HP is CCFL backlit. The major difference between the iiyama and NEC COULD be flicker.
You don't need to test the iiyama, I'm 100% sure it flickers. I haven't seen the NEC on a list of flicker free LED monitors (nor any monitor lesser than 27") but who knows.
Here's the article about flicker: http://www.tftcentral.co.uk/articles/pulse_width_modulation.htm
It tells you how to test for it. But at first it's much simpler to just lower the backlight and wave a pencil in front of a white background. If you see many individual pencils instead of a blur, a stroboscopic/staccato effect, then there's definite flicker and you don't need to test further. There's also other methods of detection as we found, like filming the screen with the iPhone 4> camera and looking for scan lines.
I really suggest you read this thread to catch up on some of the stuff we discovered and problems people have encountered.
hey guys, sorry to veer off topic slightly, but could any one confirm if, seeing as this monitor doesnt say LED backlit anywhere on the specs, can I be confident that means its CCFL backlit?
From my reading and (very basic) understanding of the specs, it doesnt say either way, whereas for other models on the site it clearly advertises LED. It makes sense that they wouldnt broadcast that its CCFL if that is outdated technology though...
Im sure i used this model number, without any pain whatsoever in my last job, (2005-2011) so want to recommend to my new job they install this monitor for me as my problems with their HP LED monitors are well documented, but want to be sure its CCFL not LED (or is there another alternative it could be to those two?), as they have already made one wasted purchase on me and i dont want it to happen again. It seems odd that a company as big as DELL would still sell discontinued technology. I wonder if it is a newer take on an older model?
Any clarification is much appreciated! thanks all!
Hello everyone, I would want to report that the screen of the new iPhone 5 also falls into the uncomfortable category
Since I don't usually need to look at the phone screen for a long period, I think I could still keep it at the moment. Though, my eyes would subconsciously want to look away from the screen asap right after I made the phone call, sent the text, etc. (that might actually help me from being addicted to playing the phone all the time, lol)
I have tried doing the "swing camera test" and found no flicker on the screen. But one thing special I noticed is that not only the screen is making me uncomfortable, the LED light on the back also gives me similar feeling.
I have tried lighting up my dark bedroom solely with that light, and seems like my eyes were irritated even if I didn't look at the light source.
And if I do the same with my iPhone 4S, things seem to look alright.