August 23, 2017 at 4:19 pm #44419
PCM2, do you have any thoughts on how the squatness of subpixels might affect the appearance of text on a display? Outside of the height of fonts, it is unclear to me what the effects of squatness might be.
You’ll have to forgive my ignorance on display and font tech. I always assumed that this stuff was taken care of by the many smart technologists involved, with no need for me to look into any of it further. What I think I am figuring out for myself is that much of it is subjective and down to personal needs, even though it is often said.
Contrast in itself might have nothing much to do with my eye discomfort when viewing text on displays. But what I’m thinking is that having the ability to get the brightness down really low while still having decently black text against a dimmed background might be helpful. That probably reads like a contradiction, but I think the main thing for me would be having the ability to get a dim display that is comfortably legible.
After taking a bunch of photos of subpixel text the other day (even with a not so steady phone camera in hand), I am now better recognizing some aspects of text which make my eyes uncomfortable. For example, at work yesterday I was easily noticing color fringing around fonts on the computer displays that I use, especially at straight edges of fonts. I was also noticing the grey pixels around text (term? grey fringing), especially at curves, such as at the top outside edge and bottom inside edge of the letter ‘O’. Both of these give text a blurred appearance to my eyes. I think this is my issue with eye focus when reading from a computer display. I have a hunch that this contributes to eye fatigue, but I don’t know to what degree. Probably the greatest contributor to eye fatigue is brightness, but once that is taken care of I still have eye fatigue with a display over time. Drastically reducing brightness seems to give me a longer window before fatigue sets in. A question that lingers in my mind here is, do monitors with a lower max brightness somehow appear more comfortable at low brightness settings due to change in contrast?
I also noticed that at a normal brightness level, such as brightness set to 20 on the U2515H, I can often see a glow around text edges, especially with white text on a black background (such as on a terminal). I also notice this on my phone to some degree with black text on a white background, which uses an AMOLED display. I think this glow around text edges might also contribute to eye fatigue, being a form of glare from backlighting. It seems to be greatly reduced as very low brightness settings.
What isn’t clear to me is how contrast comes into play. So far, my eyes feel most comfortable with a slightly lighter shade of black text on a light-medium shade of green background, with the display dimmed way down, and color temp set via software to around 4500k. It may be that I only need sharper font edges and that contrast has nothing much to do with it. The thought which comes up in my mind though is that a display with greater contrast ability may somehow contribute to sharper font edges. Not knowing anything much about how fonts are rendered and how they appear on a display with high contrast capability only leaves me wondering. I guess that I need to at least obtain a monitor with a VA panel to see for myself.
Another thing that isn’t clear to me is how pixel size and geometry comes into play for providing well-defined text edges. On my phone with a display that has a pixel size of 1.14 um, text appears sharp and smooth, with only the above mentioned factor of glow around text edges coming into play. And in the image at tftcental of text on the Acer monitor with a display that has a pixel size of 0.3113 mm, mentioned a couple of posts above, text edges appears fairly well defined without fringing. But from what I have seen so far, at all pixel sizes in the mm range below 0.3113, text edges have fringing, giving a blurry appearance. The question here that I don’t have an answer to is, at what pixel size ranges (and/or geometries) text fringing is not an issue?
To sum up here, I’m thinking that the needed characteristics in a monitor for comfortably viewing text (at least for myself) would be:
Very low brightness capability
Lack of fringing around text edges (color and grey)
Lack of glow around text edges (is somehow related to backlight brightness)
Along with the usual stuff of, lack of PWM (not absolutely sure this is an issue for me), and warm color temperature (software probably does this better than builtin monitor functionality). Blue light is definitely an issue for me.
One more thing worth mentioning is blur when scrolling web pages. I think this mostly comes into play when doing web searching, where I might rapidly look through many pages for relevant information, jumping from page to page and scrolling around in those pages. I have read that higher refresh rates can be helpful for this, but I have no experience outside of refresh rates at around 60 hz. But at this point, refresh rate is at the bottom of my list of concerns for comfortable text viewing on a display.August 23, 2017 at 5:23 pm #44420
I’m not really clear (no pun intended) on how exactly the squat subpixels on their own would affect text rendering. It means there are relatively large gaps between adjacent pixels, vertically. Then again, with a pixel density like that on a 25″ WQHD monitor, the gaps are still tiny anyway. I would imagine that it would have a subtle effect on the top and bottom edge of text. But even subtle effects could potentially affect viewing comfort on sensitive users such as yourself.
I agree that strong contrast performance can be useful if you wish to use a low brightness setting. If you’re using a very low brightness setting, it’s not useful to have the text blend into the background quite well as that would just strain your eyes. It would be better if the background was quite quite distinct from the text. Samsung’s ‘Eye Saver’ mode actually works on the premise of purposefully low contrast, for the reasons explained in my previous post, but I don’t think this would be useful at super-low brightness levels. It’s more to improve the situation at higher brightness levels where the eye would have to do a fair amount of accomodation between bright and dark content being displayed. So it would still be worth trying a lower contrast setting on the Dell and a fairly low brightness setting (like 20 – 30), just to see how you find it.August 23, 2017 at 7:10 pm #44423
I don’t know that gaps themselves between pixels would be an issue. One of the more comfortable viewing experiences I have had is on a virtual console (no X server, no anti-aliasing), where gaps in the pixels which make up fonts are easily seen from a normal viewing distance. But a virtual console has problems of it’s own. By default, text is white on black, and there is a strong glow around pixels which make up text. Drastically reducing brightness can remove the glow of text, but at such a low brightness text is less comfortable to read, being at the other end of the brightness extreme. Flipping to black text on a white background has less apparent glow, but viewing a white background drastically reduces the amount of time that I can spend in front of a display. And without an X server, there is no way that I know of to adjust color temperature. Also, since color range is very limited at a virtual console, achieving a slightly lighter shade of black on a light-medium shade of green isn’t really happening. It seems to me that most color combinations on a console are pretty extreme. There are also issues with web browsing and reading documents at a console. I can make it work in some cases, but overall it isn’t optimal (no graphics for web browsing, for example).
But maybe gaps between pixels has other negative effects. I will have to do some investigating to see what I can find.August 23, 2017 at 7:23 pm #44424
Another possible issue that I am reading about is color frame rate control. Not knowing exactly how it works or when it is being used, I can only guess. When looking at text at subpixel level, I didn’t notice any flashing between colors, but I also was looking through a phone camera with a not so steady hand. How I understand it, when a color is used that can’t be displayed due to lack of color bit depth, FRC flashes pixels at different colors in order to render the desired color. There is a lot that I don’t know here. Is 10-bit per channel material required in an application that supports 10-bit per channel before say, an 8-bit+FRC display will flash colors in order to represent 10-bit colors? Also, what happens if the video card only supports 8-bit color? Is FRC not used in that case? And I wonder if, for regular desktop use (web browser, text editor) FRC is used at all.
So many questions to get to the root of the display/eye fatigue problem.
Something that really has me curious is, I have just read that FRC happens more with green than red or blue. And while trying to work with the U2515H a week back or so, I noticed some subtle flashing going on in an image (in the green portion of the image) in my web browser. That could have been caused by something else. And it only seemed to happen for a second or two after scrolling the page. But it was repeatable. Maybe I’ll see if I can find that image again and capture it with a camera.August 23, 2017 at 8:37 pm #44428
FRC dithering is as you describe, although to be clear it is not used on the U2515H (that is a true 8-bit display). When the monitor needs to display a shade that it can’t natively display, it can alternate between a shade that’s slightly lighter and slightly darker that it can actually display. The net result is a shade that is perceived as intended. In reality, on an 8-bit + FRC display, it will be using a degree of dithering at times even if you’re just feeding it ‘8-bit’ content. The process is not perfect and there is often a degree of dithering even for some shades the monitor should be able to display natively. The fact is, though, for an 8-bit + FRC display the fluctuations in brightness where dithering is employed are generally tiny. It is very rare for this to actually contribute to eye fatigue or visual discomfort – I’m more convinced that it can on a 6-bit + FRC display where the dithering is more widespread and the brightness steps are larger. But for most users the fact a display is 8-bit + FRC should be very low down their list of viewing comfort priorities.August 24, 2017 at 3:05 pm #44439
PCM2, I had completely forgotten that this monitor doesn’t use FRC.
I may have some good news. After posting here yesterday about FRC, I continued my searching for possible issues when I came across some posts talking about pixel walk (pixel inversion). What I have read is that, in order to prevent damage to LCD pixels, there is always some voltage inversion going on among adjacent pixels. In other words, any given pixel is constantly flipping between + and – voltage, and it’s neighbor is flipping between – and + voltage. Supposedly, this shouldn’t be an issue under normal viewing circumstances. But then I ran onto the Lagom pixel inversion test page. http://www.lagom.nl/lcd-test/inversion.php#invpattern
What I saw there for image 4a is a very strong flicker, which immediately made me want to look away. I also saw some lighter flickering for image 7a. How I understand it is that when the pixel voltages flip, there can be some variance in voltage and pixel brightness, causing the flicker.
So I began adjusting the OSD settings to see if I could make it go away. What I figued out is that the flicker only happens when the U2515H is set to the ‘Standard’ color setting. So far, I haven’t found any other combination of settings for which the flicker is present. Before this point, I had played around with custom color settings in the OSD, but I had settled at the ‘Standard’ color setting, using software to drastically warm the color temperature. Color wise, that worked for my eyes, but it still was very uncomfortable to look at for some reason, which I was beginning to chalk up to blurry font rendering. I’m not so sure about the font rendering being the main issue now. I need to test further. Last night after seeing that any color setting other than ‘Standard’ got rid of the flicker in the Lagom pixel inversion test, I left the color setting on ‘Paper’. Everything seemed fine, and this morning everything seems fine.
I’ll have to give it some time to see what happens and do some more testing.
I also wonder if this pixel-walk issue might have something to do with some people feeling dizzy when using a computer monitor.August 24, 2017 at 3:19 pm #44440
It is extremely common for ‘pixel inversion’ to crop up when specific patterns are displayed. But these are very unlikely to cause any visual discomfort or in fact crop up at all during normal use on models like the U2515H. The gamma curve would be different when comparing ‘Standard’ to other presets – this inversion can occur when specific colour and pattern combinations are displayed, not just specific patterns. It is good if you can find settings that you find more comfortable, although I am extremely doubtful the ‘pixel inversion’ has anything to do with that. The ‘Paper’ setting generally maintains appropriate if not more effective blue light reduction compared to using software to do the same. It also does so without quite as much of a detrimental effect on static contrast and other image characteristics.August 24, 2017 at 3:42 pm #44442
What do you think might be a good game plan for figuring out if pixel inversion is a problem for eye comfort? As unlikely as it may be, I need to elliminate it as a possibility.
I’m thinking that I will leave the OSD settings where they are for the day (maybe making minor adjustments to brightness over the day). Color is currently set for ‘Paper’, brightness at 10, contrast at 50. And tomorrow, I will change the OSD to a different color setting that isn’t nearly as warm, maybe ‘Game’, adjusting brightness to comfort. I already know that my eyes get fatigued really fast with the ‘Standard’ color setting.August 24, 2017 at 4:03 pm #44444
There’s no need to eliminate something that is only present when specific patterns and shades are displayed. It eliminates itself, unless you’re viewing said patterns. Then it becomes very obvious indeed. It isn’t just some passive widespread flicker that is always there. On some models you can see it pretty much constantly as a sort of interference grid or interlace pattern that becomes quite pronounced when observing motion. But the U2515H is free from that sort of thing.August 27, 2017 at 4:10 pm #44470
PCM2, at this point I’m not so sure about anything.
I originally began getting eye strain a few years back on a laptop with a TN panel that is 6-bit+FRC. After that point, eye fatigue became a regular thing. Installing f.flux and setting it for a warm color temp noticably helped alot but not completely. Someone on another discussion forum recommended trying ditherig. I installed it but didn’t notice anything right away in either any obvious changes in appearance of the display or eye fatigue. I chalked up claims that I had read about ditherig helping with eye fatigue as placebo. Time went on, and I had forgotten about installing ditherig. About a month later I noticed that I had stopped getting eye fatigue from the display in the laptop. I have to think that it has something to do with ditherig, although I can’t put my finger on exactly how ditherig helps. Nothing else changed which could account for it, not even any driver updates.
Then I decided that I might like to start using a desktop again for some applications which are better suited for a desktop. Virtually everything I read on monitor recommendations for primarily text use pointed to an IPS display. I intially went for a U2414H, and out of the box it looked very comfortable. Unfortunately it had severe defect, and I returned it before having time to evaluate how well it would work for elliminating eye fatigue. I can’t put my finger on why the U2414H looked so comfortable, but I used it for a full day with no eye fatigue at all before sending it back.
At that point I also felt that I would like to have more working space, and I ended up reading reviews here, which lead me to the U2515H. It looked nice out of the box, but something also seemed very uncomfortable about it. I had already dropped the brightness to 20 right away, and I was thinking that the brightness couldn’t be the issue. Lowering the brightness a bit more seemed to help a little but not completely. After moving through the color presets and feeling that none of them looked comfortable, I installed redshift to warm the color more. I also tried a range of brightness, contrast, and color settings in the OSD, with and without redshift. But from the getgo with this monitor, I was feeling eye fatigue coming on. There was no point to look for anything for disabling dithering (which seems to have worked well on the laptop TN display) since this monitor is 8-bit without FRC. Changing to the ‘Paper’ setting a few days ago initially seemed to help, but I began feeling eye fatigue again pretty quick. I can’t put my finger on why this monitor is so fatiguing. It isn’t font size, distance, or room lighting (more on that in a minute). And apparently it has nothing to do with pixel inversion, since the ‘Paper’ preset shows no flashing in the lagom pixel inversion test but is still fatiguing.
In the meantime, I had also decided to try a monitor with a different backlight type, which lead me to the LP24080ZX. This was a used monitor purchase, obviously. And unfortunately the first one that I received had a bad pink tint to it. The replacement arrived a couple of days ago, and I have been using it since, with no eye fatigue as of yet. Right away it felt more comfortable to my eyes than the U2515H, and the only thing that I have done is to lower the brightness. Even with the brightness at max, while it looks too bright, it doesn’t seem to hurt my eyes. I am using it with very similar font sizes as the U2515H (had to do some scaling with the U2515H), same room lighting, same distance. I have also tried using it close in and with the lights off, and I don’t feel any fatigue, where with the U2515H, I eventually feel fatigue no matter what I do. On this second LP24080ZX there is some color shift across the panel from pink to green, but it isn’t severe. Also, with anti-aliasing off, fonts don’t look as mishaped as on the U2515H, but with anti-aliasing on fonts look very noticably sharper on the U2515H. Also, moving through the color presets on the LP24080ZX, while I have a preference for a warmer display, even at coolor settings I don’t feel any eye fatigue.
And again I am perplexed on the cause of the eye fatigue issue. One thing that I have read is that the LP24080ZX uses a A-TW polarizer, which some users from the past have associated with eye comfort. I don’t know if it has anything to do with it or not, honestly. It also seems unlikely to find one of these monitors that doesn’t have the strong pink tint to it, and it may be the case that the one I have will develop it over time. For now I will continue using this monitor. But I would eventually like to find a monitor with more working space, improved sharpness for text, and is still comfortable to the eyes. But at this point I don’t know which characteristics to look for. For eye comfort alone, a laptop with a crappy TN panel and dithering disabled works for me, and a nearing 10 year old LP2480ZX seems to be working for me. I will report back on eye comfort with the LP2480ZX after more time with it, just to be sure.August 28, 2017 at 7:15 am #44471
So one big remaining culprit is the backlight. Thus coming back to my initial advice and some of my follow-up posts..September 11, 2017 at 4:26 pm #44581
Just reporting back. Still no eye fatigue/strain with the old LP2480ZX. I ended up with the brightness set to 140 cd/m^2 and no other changes or software solutions. That’s good enough for me.
Also, after using this monitor for a while and having given the eye fatigue issue lots of thought, I started to clue in on other sources of milder eye fatigue. My workplace is lit by fluorescent lighting and way too much of it, in my opinion. I asked my coworkers if any of them had eye problems at work. Some of them said that they do, with one person saying that she gets headaches at work, which she thinks is to do with the lighting. We agreed to turn off some of the lights, and everyone seems happy with it. So now I don’t get any eye fatigue at work either. Maybe something that is more relative here is that among the monitors used at work, which are all led backlit, none of them seem to give me any eye fatigue, after having kicked the main source of eye fatigue. All the monitors there are older business class cheapies with low brightness capabilities (I looked up the specs for each), standard resolutions (nothing high res), and standard gamut. So text clarity and color gamut isn’t the main issue. I think that alot of monitors being made today are just way too bright. But what I don’t understand here is why a bright monitor is still fatiguing when the brightness is drastically reduced. It seems that something else is at play.
To sum up, for anyone looking for some relief from eye strain, I would say from experience to find a monitor that isn’t very bright and reduce any bright room lighting. Also, keep an eye out for other sources of eye fatigue. Even reading paper under bright light or too dim light can cause eye fatigue. And do give software solutions a try, such as f.lux and ditherig. I can understand how f.lux is helpful, but I have no idea why ditherig is. After having installed ditherig on my laptop (a dim 6-bit+FRC TN display) I noticed over a couple of weeks time that I no longer got fatigue from using it.
I still don’t understand too much about all this eye fatigue stuff, but I’m glad to have found solutions that are working for me. But the real test is yet to come. I still haven’t started back with long hours of coding in front of a screen.September 18, 2017 at 11:10 pm #44635
What is dithering and how did you install it? Is it a software?September 19, 2017 at 6:55 am #44636September 20, 2017 at 5:50 pm #44639
Fuzzyeyes, I also suffer from eye strain and also work many hours infront of a screen. Like you I found I have become at least slightly sensitive to florescent lighting. The color spectrum of the ambient light also plays a role for me; using the so-called natural light bulbs seems to have the best results. PWM in my monitors is also now bothering me. I replaced my monitors with models which don’t use PWM. Low blue light also helped. With regards to the brightness of the screen, I found that this was not so hard and fast a rule. Too low a level and my eyes initially felt more relaxed because they weren’t staring directly in to a light bulb all day, but the longer term effects of a too dim a screen (vs a too bright one) were worse for me. Setting a slightly lower room illumination and a mid-level screen brightness was, for me, the trick. Well that and a new monitor with the features I mentioned above.
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