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Hardware

Will Flat Screens Save Your Eyes? 49

Posted by timothy from the the-human-body dept.
An unnamed corrrespondent asks: "Are LCD flatscreen monitors better for your eyes than CRT's? Have studies shown that LCD's reduce eyestrain, red-eye, or other eye fatigue compared to CRT monitors due to less radiation, no flicker, or other differences in the technology?" Studies aside, I certainly find it more comfortable when working for hours at a time to be staring at a nice TFT LCD than even a high-quality CRT, which is one reason that I'm growing resigned to laptop keyboards.
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Will Flat Screens Save Your Eyes? More

Will Flat Screens Save Your Eyes?

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  • I have next to no experience with modern LCD's, but I do know that they have not used crystals that can move fast enough to keep up with video/games/animation. Though, the quality now days is, likely, not bad, I would guess that if you sat a good CRT next to an LCD and played a game on both, the CRT would win in the bluriness factor.

    Something I like to do is go into a Radio Shack, Best Buy, or your local computer shop and test drive a system with an LCD on it. The shop will probably have some sort of demo movie running on the machine that will give a pretty good idea of what the screen will look like during a game.

    All that aside, I would still love to get a good LCD at work (I don't game there). Staring at a CRT for 8+ hours daily gets to you after a while.

  • I think you might want to checkout the reccomended resolution for the monitor. If the fonts look screwy, then it's just that the video card is running the monitor at a different resolution than the monitor runs natively. Switch the videocard's resolution to match the monitor's resolution.
  • Peripheral vision is more sensitive to flickering than regular vision.

    Therefore even with my monitor set at 75Hz I get annoyed by the flickering when I'm looking away from the monitor but with it still in my peripheral vision.

  • SGI 1600SW - 17" extra-wide display for ~ $1500 direct from SGI, ~$1400 from dell.com (out of stock). Make sure you get the multi-link adaptor. You'll also need a video card that supports DVI (and LCDs, some cards have DVI but can't run some LCDs).
  • The T86's are down to ~ $1k USD. See ubid.com and pricegrabber.com.

  • There's one other significant difference between monochrome and color monitors.

    If you look at two monitors that were produced, say, 10 years ago, you'll notice some significant differences. The color VGA monitor, even at the default 640x480 resolution, still has somewhat fuzzy text. In contrast (pun intended), the monochrome monitor has very sharp text.

    This is because of the dot pitch used on those older monitors, and the whole issue of having a screen mask (dots commonly, or wires with a Trinitron display). Because monochrome monitors didn't have a mask, there's nothing that diffuses the electron beam striking the phosphor. There are also no focus and alignment issues with multiple electron guns.

    Back at school, we had 19" monochrome monitors for our Xterminals, they rocked! Too bad you can't buy that kind of stuff anymore.

    Of course, now I'm completely dependent on my LCD screens (SGI 1600SWs of course). I am so spoiled, I don't know how I managed without colorization of program code and color-ls.

  • Dead pixels are not all that frequent, at least for me. My Dell 1024x768 display has one bad pixel, and I notice it only rarely.

  • You might want to look at the Apple LCD display. It uses a digital interface (Apple Display Connector) between the video card and display, avoiding the problems inherent in LCD displays that are driven by analog video.

  • Re:May save your eyes but... (Score:3)

    by Detritus ( 11846 ) on Sunday February 18, 2001 @10:38PM (#421476) Homepage
    It is theoretically possible. Apple uses the ATI Rage 128 and Radeon AGP cards. These are OEM versions that include the Apple Display Connector (ADC). The problem is how to get one without ripping it out of a Macintosh. Another question is whether or not the drivers for the PC versions of the cards are compatible with the Mac versions of the cards.

    It would be nice if PC vendors adopted the ADC. I'm not sure if there are any patent or licensing issues. When I got my Apple LCD display, I took it out of the box, put it on the desk and attached a single cable to the Mac. Turned on the Mac and everything worked perfectly.

  • I don't know about you folks, but all of the desktop flatscreen LCDs that I've seen have terrible font quality! Everything is all blurry!

    If I have to use one, it must be set at 800x600 just to half-read the text on the screen. My laptop has better quality fonts at 800x600.

  • I believe the flicker threshold for most people is somewhere between 60 & 75 Hz (though I don't have any references to back this.) For the same reason, the frame rate in games like Quake III don't give additional perceptual improvement beyond 75 fps. As long as you set your monitor's refresh rate to 85 Hz or higher, monitor flicker shouldn't be a problem.

  • They _would_, if I wanted it.

    The aspect ratio is all wrong. It's like watching a movie.

    When I'm doing admin work, I don't want to watch a movie. That's what the 36" TV in the den is for. %-)
  • As someone who works for a rather large telco firm, we get our hands on decent displays. All of the admins in my group have one of two monitors: Either Sun's 21" premium flat CRT or Sun's 18" LCD.

    I myself chose the 21" CRT over the 18". Not only is a) the resolution higher; b) the screen bigger; but c) it looks _sharper_.

    Sun's 21" tube is a Sony Trinitron OEM'd. And it's probably the BEST 21" tube I've ever used.

    We're split about half-and-half between the CRT's and LCD's. Truthfully, the LCD is a bit brigher (albeit fuzzier), but working a long day on the CRT tube is painless. It's a GREAT tube.
    I've worked only for a few hours on the LCD's at a time, not a full, long day, but I truly missed my CRT.
  • One thing I've heard is that CRTs give the appearance of an image where it really isn't (either in front or behind), therefore making it impossible for the eyes focus in the image. With LCDs, this doesn't occur and they should theoretically be easier to look at. I know I prefer my 12" laptop LCD over a 15" Trinitron any day.
  • ...is super easy on the eyes.

    last semester worked on an AI project for 61 hours, with only minor sleep. my eyes were fine, whereas my buddy had a brutal headache. his 19in crt had done him in.

    even tho i've had my IBM T86 for 6 months now, i'm still impressed how good it looks.

    if you can afford one, don't hesitate, go an get one. it'll be worth the money. paid $4000 (canadian) for mine with not a single regret.

    peace.
  • actually, my summer job paid about 20 grand... so i figured that since i stare at my monitor all day long i'd do my eyes a favour.
  • i'm not on OSAP, but you're right, it's paying for my bro's med school.

    don't live with the folks either, don't think i could handle that, hahahah.
  • Newer CRT's don't radiate more than the wires we've all got running through our walls. and that too is significantly less than the 60W light bulb you've got hanging over your head, emmitting a faint glow.
  • If it looks sharper on the CRT then it's because you are not using digital plug for the TFT. I've been using both CRT and TFT (on laptops= for some time and good TFT with digital link beat the crap out of any CRT, including the best Sonys out there. Once every pixel is perfectly visible and square, it can't get much sharper :)
  • I used to be a fan of big heavy PCs with huge CRT screens. Then I was forced on day to go for a laptop, so I bought what was a nice and expensive Dell laptop with 14" TFT screen.

    Now I have never looked back at desktop PCs again ! My latest work machine is another Dell laptop with a 15" 1400x1050 TFT. The picture is so beautifull and sharp :) Although the resolution seemed to be a little too high for the screen size, it's still much more readable than anything else and provides plenty of screen real-estate. Now going back to work on a CRT, even a good one, is a real pain. Also I like the ability to have one and only one PC at work and at home (no more syncing of files and emails to do)
  • You tend to see the flicker when you move your eyes, which can hurt quite a bit if you're reading for a long time.
    --------
    Genius dies of the same blow that destroys liberty.
  • This is Apple. Of *course* there's patent or licensing issues. :-(
    --------
    Genius dies of the same blow that destroys liberty.
  • Some of the issues around LCD displays such as viewing angle are a function of some of the underlying technology. Here at work I have an NEC XtraView. The XtraView screens use a different (and presumably more difficult to fabricate) electrode structure that provides a different crystal orientation. Colors and brightness are much more consistent across the screen than on the less expensive NEC displays. Also, while the brightness drops off as you get more than about 30 degrees off-axis, the color values remain quite accurate through the entire viewing range. The XtraView is easily the best LCD panel that I've experienced.

    But on the 15" LCD, you pay about $300 more for XtraView than for the simpler display. That difference alone would pretty much pay for a 17" CRT with a similar viewing area.

  • Re:Bring back monochrome. (Score:3)

    by lizrd ( 69275 ) <[su.pmub] [ta] [mada]> on Monday February 19, 2001 @11:26AM (#421491) Homepage
    My eyes were never as bad when we used monochrome monitors and text only apps.

    And my eyes were never as bad when I was 15 years younger either. What's your point?

    Black on white displays...just another thing that we have Mr. Jobs to thank for. Yet another Apple innovation that looks looks cool and really doesn't serve much purpose [especially now that screens don't burn in so easily].
    _____________

  • You may be used to white text on a black screen, but a normal user is used to the text being black (like ink on paper). I personally can feel my eyes relax when I switch between black on white and white on black screens.

    The really optimal colors are black text on a wheat background. It's not as bright at white, and still has a very good contrast to it.

    I'll also bet your eyes were younger when you were on monochrome displays :)

  • > One thing I've heard is that CRTs give the appearance of an image where it really isn't (either in front or behind),

    Looks like behind (just try to focus on a piece of dust on your screen and compare to where the image is: looks like some 3mm behind).

    Solution: keep your screen dust free, so your eyes won't find any point of reference on the glass surface, and the only thing it notices is the image. If the image is at the "wrong" place, make sure the eye does't know where the right place should be...

  • Yes, there is a speed beyond which the human eye cannot track changes in briliance (ie ammount of light) fast enough. Basically nervous conections have a minimum recovery time between passing two nervous impulses - if i'm not mistaken, for neurons it's about 18 ms (i got this from my neural networks class some years ago). So, even if the optic nerves were faster than this, the information couldn't get to the brain any faster.
    You forgot that the retina isn't just a plane of pixels, it's also an image processor. It contains cells which detect edges and movement. You also forgot that your eye does not stare at one single place on the screen, it is almost always scanning to different spots.

    Motion of the eye introduces the problem of stroboscopic effects. A refresh rate which is more than fast enough to be undetectable to a single detector cell your eye is quite a different matter if your eye is panning fast enough. Instead of seeing shapes and edges moving across the field of vision, bright areas in dark fields leave a string of bright dots on the retina while dark areas in bright fields do something similar to (but not exactly) the opposite. Motion-detector cells, which are evolved to deal with more or less constant illumination, don't work properly under such conditions. The motion cues and other little details which your eyes ought to have to aid their tracking across the page are subtly wrong. What this leads to I don't know, but I am aware of some research which showed that people's eyes take longer to scan to particular words on a printed page under flickering fluorescent light than under incandescent light (no word on what effect high-frequency electronic ballasts might have had).

    So far as stroboscopic effects are concerned, there is little difference between 60 Hz and 85 Hz. You could eliminate this with long-persistence phospors, but nobody wants to watch their screen smear into an indecipherable blur every time something scrolls. Face it, the CRT is far from an optimal display interface to the human eye.
    --
    Knowledge is power
    Power corrupts
    Study hard

  • How does that happen? You're a student, yet can afford a $3k (US) monitor?

    ----
  • I'll contribute my ancedotal experience... I just bought a Toshiba 2805-201 (13.3 TFT LCD). Up to now, I had been a happy user of a Gateway CrystalScan (17") since Feb 1997. Yet after only two days of using the Toshiba, I am spoiled. Text is crisper, my eyes focus easier, overall: much less strain. I didn't realize how much better my eyes liked the LCD until I went back to the CRT -- what a difference! It actually was uncomfortable to use the CRT (I had to squint).

    I don't know the science or the stats, but I know my eyes: TFT LCD bests any CRT I've used.

    That said, unless I could get 1024x768 resolution I would even dream of using a LCD (I need the space!).

  • That's because CrystalScans SUCK.

    Perhaps they do, but you failed the reading comprehension test: my point was not the relative merits of the CrystalScan, but how short-term exposure to the Toshiba LCD changed my appreciation of what had been satisifactory previously.

  • How does that happen? You're a student, yet can afford a $3k (US) monitor?

    University education is ALOT cheaper here in Canada, the Government pays 80-90% of tuition fees. Some people live with their parents too, so they don't have to pay rent/food/bills/etc, leaving them with money to spend on toys.

    As for the LCD vs. CRT thing, I have a laptop with a 15" 1400x1050 display, it's crisp like you wouldn't beleive. The viewing angle thing is the only negative that I have with them. Though, it's advantages more than makes up for its for it's disadvantages (lighter, smaller, no alignment/rotation/focus problems, no flicker-headaches, etc.).

  • That is the visible threshold. But, any optician or cognative scientist will be able to tell you that constant flicker will affect you after a prologned period of time, where "prolonged" is less than an hour.
  • As a total amateur in this area, but having read something about it:

    Yes, there is a speed beyond which the human eye cannot track changes in briliance (ie ammount of light) fast enough. Basically nervous conections have a minimum recovery time between passing two nervous impulses - if i'm not mistaken, for neurons it's about 18 ms (i got this from my neural networks class some years ago).
    So, even if the optic nerves were faster than this, the information couldn't get to the brain any faster.

  • EMP Scream (Score:3)

    by Aceticon ( 140883 ) on Tuesday February 20, 2001 @06:29AM (#421501)
    What worries me about CRTs is the ammount of Electro-Magnetic, non-visible spectrum energy they emit.

    The basic principle of CRTs is to produce light by firing high speed electrons against a "brick wall" (actually lead and glass if i'm not mistaken). The problem is that, when a high speed electron is quickly decelerated (as in hitting a solid surface), it will release energy across the whole Electro-Magnetic spectrum (what i call an EMP Scream).

    Guess what - i'm siting just behind one of those brick walls, getting bombarded by thousands of bilions of electrons per minute. The tought is not very conforting ...

  • flickers noticably when refresh rate is set too low

    I've always been a little curious about this; I know the brain can subconsciously (and sometimes consciously) see the image refreshing if the refresh rate is too low, but does it really get that much better if the refresh rate is set really high? Does the eye ever get physiologically incapable of seeing it refresh?

    Personally I like my flatscreen at work, simply because I have to look at it for 12 hour stretches at a time, and it's a lot easier on the eyes. A good crt has much better image quality I think though.
    --

  • From: http://www.feds.com/nll_lib/ctd/ctd0706.htm [feds.com]
    cyberFEDS - CTDNews - Vol. 7, Issue 6 - June 1998

    >>Comments interspersed are mine.

    Ergo jury on flat panel displays still out

    The emergence and initial success of flat panel displays have raised question about their ergonomic design and health impact, particularly in comparison to the conventional computer monitor.

    Most, if not all monitors, bundled with computer systems today are cathode-ray tubes, which project a beam of electrons onto a screen to produce an image.

    Flat panel displays (FPDs), which remain secondary purchases for computer users, produce an image when an electrical current passes through a liquid or gas contained between two plates. Variations include liquid crystal, gas plasma and electroluminescent FPDs.

    The benefit of FPDs, according to manufacturers and some ergonomists and researchers, is the visual improvement over cathode-ray tubes and maximized desktop space.

    On the matter of size, FPDs are designed to be more "flat." They are not as deep as conventional VDTs and, therefore, allow computer users more workstation space. For example, a 20-inch cathode-ray tube could be about 20-inches deep, while a comparable FPD could be only a couple of inches thick.

    Like a mirror, FPD could be mounted on a wall or the back of a cubicle.

    That flexibility and the reduced area to accommodate monitors pleases many ergonomists, particularly as computer workers are being asked to work around CPUs, keyboards, mice, printers, modems, telephones, external hard drives, etc.

    >>Amen. I just bought my first laptop last year, and I can't say enough good things about the TFT monitor. The display certainly seems easier on my eyes. The flexibility component may have more to do with the fact that it's a laptop, though.

    However, the health impact is not as convincing. James Greeson, president of Ergonomic Solutions Inc. and editor of the International Standards Organization's FPD standard, said, "It's a kiss-your-sister kind of story. There's no conclusive scientific evidence that flat panel displays are visually more dangerous or superior to cathode-ray tubes." (The flat panel display standard is ISO 13406.)

    He also noted the FPD image is pixelated, meaning images -- letters, numbers, symbols, graphics, etc. -- are made up of tiny dots, which can be seen in some cases.

    "This is not an ergonomic defect. It's not dangerous. But it is an image quality detractor," said Greeson.

    >>This effect is noticeable on my screen, but not terribly distracting, IMO.

    Leading manufacturers like DTI (an IBM-Toshiba partnership), Fujitsu, NEC and others argue FPDs are vastly superior to the tubes. In their promotional literature and posted on their websites are claims of how FPDs dramatically reduce eye strain.

    Recent studies have highlighted increased glare and reflection problems associated with FPDs, but the studies also reveal general user preference of FPDs over CRTs.

    >>The glare issue is easily resolved. Tilt the screen away from the light. I had lots of trouble with glare in office buildings. The clunky CRTs were difficult to move. Beyond that, there are only so many positions possible with something that heavy and ponderous. Fluorescent light is also tremendously hard on my eyes, which is why I avoid office buildings these days. :)

    No less important in the debate over whether to upgrade to flat panel displays is the price. They command a hefty price tag in comparison to a CRT. Market researchers estimate an FPD to be about five times the cost of a comparable CRT, though it may be only three times the price by the end of this year.

    >>All of my praise aside, were I to buy another desktop computer, I would not now shell out the extra dough for a flat panel display.

    FPDs are gaining popularity in the desktop publishing, medical financial and military fields, the research indicates.

    >>Perhaps that statement indicates a preference for FPDs by those who work with graphically-based applications. Perhaps the sharp text is more desirable to those who code. (My work leans more toward desktop publishing, so maybe this explains my preference for the TFT monitor.)
  • Single colour frequency light on a black background is far more easier on the eyes than these colour displays, particularly with almost everthing insisting on white backgrounds at the moment.

    At home I use text-mode applications exclusivly, with all text in a single primary colour. I'm on the lookout for a cheap dumb terminal (preferably green on black) for the spare room.

    My eyes were never as bad when we used monochrome monitors and text only apps.

  • IIRC, 72 Hz is considered the lowest flicker-free frequency. Personally, I can catch my console flickering only in my peripheral and only when the screen is solidly colored (like with ntsysv), and that's 68 Hz. X is fine at 75 Hz, and horrendous at 60 Hz.

  • Why won't they get you Sun's 24" Monitors?!?

    Actually, I've been lusting over one myself, but I can't begin to justify the $2200.

    Hey, I just noticed the 24" crt is LESS than the 18" lcd. So why not opt for the bigger crt?

    24" Sun Monitor [sun.com]

  • I've been curious about these Apple LCDs. Are they usable with regular PC's? I remember several years ago, you could use PC monitors with Macs via a special connector, but not the opposite (Mac monitor on a PC). Has this changed at all, cause I really like those apple flatscreens!

    -mdek.net [mdek.net]
  • A properly driven [read: digital] LCD, say the Apple Cinema Display [apple.com], is brighter and clearer than a CRT. A good quality CRT (Sony Trinitron or Mitsubishi Diamondtron) will be the next best thing, and as far as price/performance goes, the CRT wins hands down.
    I spend all day looking at a LCD, even if it is only a passive matrix, and i find much easier on the eyes than a CRT, the exception being when stuff moves around, and a good active matrix pretty much eliminates this problem.
    As far as EMF and power consumption goes, LCDs come out far better.
    If price was no object, then i'd much rather have a high quality LCD (have you actually looked at a Cinema Display with your own eyes, rather than reading reviews) but for my home PC, there's no way i'd fork out the $$$, and instead will get a flat screen trinitron.
    -- kai

    Verbing Weirds Language.
  • One thing I notice is that there's considerably less glare with an LCD screen. Possibly because, unlike a rounded CRT tube, I can find a position for the LCD which doesn't reflect the ambient light. Whatever the reason, it helps my eyes considerably.

  • lcd's are a so-so compromise (Score:3)

    by fatmantis ( 218867 ) on Sunday February 18, 2001 @12:41PM (#421510) Homepage
    let's look at some bad points for each type of display:
    1. tft:
      • still has a limited angle-of-view
      • frequent dead/broken pixels
      • artificial looking crispness of each pixels
      • wildly expensive

    2. crt:
      • flickers noticably when refresh rate is set too low
      • ghosting and pincushioning with age
      • fragile, yet large and heavy
      • eats up power.

    but what really matters most to me is the fidelity/luminence of a given display's ability to show red. this is where tfts fall short.
  • I prefer my 14.1" TFT laptop screen over my 19" IIyama CRT, because it is much sharper and easier on my eyes. I'm considering buying a large TFT (18") for my regular PC, but I'm hesitating because I also want to play games on it. Is TFT suitable yet to play games or watch DVD movies ??
  • Comment removed based on user account deletion
  • Gee...and you mean your laptop doesnt has an old dube monitor?wow...id like to see that

  • Re:May save your eyes but... (Score:3)

    by snellac ( 314920 ) on Sunday February 18, 2001 @02:38PM (#421514)
    I don't know what OS you use, but if you use Windows, you should try out Microsoft Reader [microsoft.com] and see if you see a significant improvement in readability of your fonts within the application with its ClearType technology, which really improves fonts on LCD screens. I have also heard that ClearType will be included in Windows XP when that is released.

    If you use Windows and don't want to download Microsoft Reader, I suggest trying out Steve Gibson's ClearType Sub-Pixel Font Rendering Demo, available here [grc.com], which is a small application to demonstrate ClearType technology.

    Also, Slashdot (last year) ran an article on ClearType technology here [slashdot.org].

  • Are LCDs better for you? (Score:4)

    by snellac ( 314920 ) on Sunday February 18, 2001 @02:30PM (#421515)
    There is a great page of Health & Safety Monitor FAQs at http://www.csf.org.uk/csf/monitors/monitorsfaqs.ht m [csf.org.uk].

    Quoted directly:
    21. Are LCDs better for you?

    There is some research work that has been carried out that suggests that LCDs should be easier on the eye than CRT monitors, because the eye finds it easier to focus on the sharply-defined pixel edge. One or two small research projects have found evidence to support faster reading speeds on LCDs. Anecdotal evidence also points to users being happier to spend longer periods looking at LCDs. There are also reports from users that they can find it difficult to constantly switch between the two technologies.

    In the future, LCDs are likely to run at higher resolutions than CRTs, with consequent improvements in reading speed and accuracy.

    -snellac

  • One factor of the issue that I have not seen addressed, is the fact that CRTs produce a whole bunch of electromagnetic radiation. I don't know how much, and it would be nice to see it quantitized. I would guess it would be a pretty large amount. I mean, think about it, the CRT is mostly a big phreakin electron gun, aimed at your head. Even if most of these electrons stay on the right side of the glass, a few must slip through. -------- Off topic: I am suprised Nikolai Tesla remained as healthy as he did when he was letting AC pass through him all the time. I think he also found X-rays to be relaxing, and would bathe in them for long periods of time. Mmm, nothing like some good eccentricity. By the way, Tesla was much more influential to today's uses of electricity than Edison was. There was actually a rivalry between the two. If you read about it, you'll find that Edison was a bastard, and does not deserve half the credit he gets in today's sad failure called "public school".


    -------
    loosing all hope is an ideal

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