Which displays are good for the eyes?

Discussion in 'Displays' started by John Roger, Aug 20, 2004.

  1. John Roger

    John Roger Stunt Coordinator

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    Just a little curious.There is an age old saying, if you watch TV too much you'll have to wear glasses.

    Is is true only for CRT direct views.What about projection,LCDs and Plasmas.Are they eye friendly?
     
  2. Jack Gilvey

    Jack Gilvey Producer

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    I thought it put hair on your palms. Maybe I'm mixing it up?
     
  3. John F. Palacio

    John F. Palacio Supporting Actor

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    This is an excellent question.

    I don't know if a formal study has been made, but based on the way displays and the human eye work I would guess that displays with the most persistence would be easier on the eye. Just a guess.

    This would make the Plasma's and 3 chip LCD's the most eye friendly, CRT based sets # 2 and DLP's # 3.

    Film displayed in theaters with its 48 FPS (24 frames, 2 exposures per frame) rate are probably not very good in that respect.

    George Lucas' ShowScan (70 mm film at 60 FPS) is probably the best. (Actually the best in a lot of respects)
     
  4. John Roger

    John Roger Stunt Coordinator

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    Maybe true.But what about radiation?Aren't CRTs high on radiation?
     
  5. Bob McElfresh

    Bob McElfresh Producer

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    I think this is a "Mom" saying and I thought it was if you sit too close to the TV it could damage your eyes.

    Radiation - well millions of people sit very close to CRT based computer monitors and have done so for years with little-to-no radiation issues. Ergonomics (poor seating) is a much more common problem.

    I would not suggest you select a display technology based on radiation/eye damage. There is little-to-no difference in potential damage between CRT, DLP, LCD or Plasma (as far as I know).

    A bigger concern would be sitting too close/buying too big to any of these. This causes 2 known problems:

    - eye strain from having to move your eyes back and forth

    - eye strain from watching TV in a dark room so as scenes go light/dark your eyes have to constantly adjust to changes in lighting.

    This thread on What Size RPTV has a chart that can help you pick the proper sized display based on your seating distance to help prevent eye-strain.

    Hope this helps.
     
  6. andrew markworthy

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    I don't know about the radition effects (though sitting close to anything giving off a magnetic field like a CRT probably isn't a good long term idea). However, with regard to lighting and regardless of the type of screen, you should have another light source in the room. If you watch anything in total darkness and then move your eyes away from the screen (which you will do a lot whether you realise it or not), your eye muscles and lens are having to do an awful lot of unecessary stretching and relaxing and this is not good. Similarly, you shouldn't just read with a reading light on - you should have another (gentle) light source in the room so that when you look up from the page your eyes don't have to make too much adjustment.

    This may sound like very fussy advice, but remember that slight effects can cumulatively have a big impact when repeated over decades.
     
  7. John F. Palacio

    John F. Palacio Supporting Actor

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    andrew markworthy says:
    Maybe so, but this is the way we all watch movies in the theater. This is also the way I watch CRT displays at work usually in 10 to 14 hour workdays (sometimes longer) wearing contacts and I personally do not experience any undue eye strain. It is possible, even probable, that some people are more sensitive than others in this respect. The iris of the eye would be the only thing that would be stressed by going from dark to bright and not by a lot since it is fairly wide open when watching most properly adjusted displays.

    Certainly going outdoors during daylight hours and back in dimly lit indoor areas would create greater degree of stress on the iris.

    As for the radiation issues this has been a source of debate for a long time and has never been totally resolved. Suffice to say that CRT's will emit a small amount of X-rays because of the high velocity electron gun whereas LCD's and plasma's won't. All electronic devices will radiate a small amount of EMF regardless.

    As for seating too close, take a look at the SMPTE (Society Of Motion Pictures and Television Engineers) and the THX recommendations and see the huge screens that are suggested.

    Check this link: http://www.myhometheater.homestead.c...alculator.html
     
  8. Jack Briggs

    Jack Briggs Executive Producer

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    There's a solution to all this, regardless of the type of display. To watch a monitor properly you need some sort of bias lighting to reduce the strain on the eyes.

    What's happening is that when you sit in a darkened room watching a CRT, your eyes are straining — the pupils are not being allowed to dark-adapt properly. When the lights are lowered, the pupils dilate to allow for proper light-gathering. But the CRT throws this out of whack, causing the pupils to respond erratically, causing strain on the eyes.

    This can cause longterm wear.

    Go to a hardware store or electronics store and look for a ten-watt lamp that you can install behind the monitor. The backdrop provides the eyes with a constant standard of light, reducing the "confusion" your pupils are experiencing.

    Besides, it looks terrific. You'll never want to go back to a completely darkened room. Unless, of course, you get into front projectors.
     
  9. John F. Palacio

    John F. Palacio Supporting Actor

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    What exactly wears?
     
  10. Bob McElfresh

    Bob McElfresh Producer

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    This confused me as well (that there seem to be different rules for your living room than a commercial theater) My only guess is that there is so much more light output in a commercial theater projector that it is rarely totally dark and the average illuminuation is higher than it would be in your living room.

    I remember one of the HT magazines talking about this. The author acknowledges that while a totally dark room was recommended by the purists, it's just unpleasant.
     
  11. andrew markworthy

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    Amongst other things, your eye muscles and lens (remember the human lens stretches and relaxes, it doesn't stay rigid and move in and out like e.g. a camera, or for that matter an octopus's eye).

    Note that the extra lighting doesn't have to be all that great and it won't mar your pleasure (unless you really have a thing about being in total darkness). As Jack has correctly said, a very low wattage bulb should be fine.
     
  12. John F. Palacio

    John F. Palacio Supporting Actor

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    Well... I am going on 62 years old, have been staring at monitors in dimly lit or totally darkened rooms for over 30 years now and exhibit no ill effects. Planning to keep at it for a while more.

    So much for long term ill effects!

    We take breaks in the US too. I would assume TV watchers do to. After all we all need to go to the bathroom, eat, stretch, etc.
     
  13. John F. Palacio

    John F. Palacio Supporting Actor

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    Sorry but you are misinformed as to how the human eye works. The "lens" is used for focusing and does not do any work when adapting from dark to bright light. The iris or pupil does that. And the eight "eye muscles" move the eye up-down, left-right and obliquely. Again nothing to do with light intensity.

    So if anything is going to wear out is the pupil, which does become slower with age (like the rest of us)
     
  14. ChrisWiggles

    ChrisWiggles Producer

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    The desire for bias lighting exists for small screens. First, I want to assume that we are talking properly calibrated displays that are dimmer than their out-of-the box counterparts.


    I don't know where that guess came from, but in good theaters, it should go as close to totally dark as possible, though for many reasons this is rarely ever achieved. With a large FP screen, backlighting is not usually necessary, because the screen takes up such a large part of your FOV. With a smaller screen, your eyes won't adjust to the changes much, and will stay fixed more on the dark room, and a small, bright monitor will look quite bright and cause faitigue in that way.

    Lastly, the issue of fatigue due to rainbows, or CRT flicker is an interesting one. The least fatiguing displays I've used are 3-chip DLP and LCD/LCOS type projectors.
     
  15. Ted Lee

    Ted Lee Lead Actor

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    i don't think i've ever been to a *totally* dark movie theater. from a practical pov, it's impossible anyway - there's too much light coming off the screen. afaik, all theaters i go to have light-scones on the walls as well. and i've specifically looked for them, so i know they're there.

    eyes dilate ... that's a simple fact. your iris expands with less light and contracts with too much light. and it does so very quickly. if you don't believe me, shine a flashlight in someones eye and watch how quickly the iris moves. watching tv in a completely dark room has the same effect.

    -- off topic --

    i don't know how anyone can watch tv in a totally dark room. i literally start to get a head-ache. i always have some sort of bias lighting going on. i've tried all sorts of methods; light from the kitchen, from my office (which is behind my living room), the hall-way, dimmers on my floor-lamps, etc.

    but ... just last night ... i think i found the perfect solution. my wife bought a couple of wall-mount candle holders from pottery barn. i put a couple of them in a spot where they look good and won't reflect on my tv. they provide the nearly perfect amount of ambient light. color me stoked! [​IMG]
     
  16. ChrisWiggles

    ChrisWiggles Producer

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    If you have a small viewing angle, which is usually the case with smaller TVs because people sit too far away, bias lighting can be helpful, but do take note that if you're picky, you'll want to investigate true D65 lighting so as not to skew your perception of the video, and also keep any of the light from shining directly on the screen.

    With a large FP setup of sufficient caliber such that you can sit with a large FOV that mimicks a theater, you shouldn't need to use any bias lighting. *any* light in my theater destroys one of my projector's primary capabilities: the ability to show true, total black. I've covered all the lit displays and LEDs on my electronics with tape, especially on the ones that you can't turn off like receiver readouts (those can be friggin BRIGHT), as they destroy the complete black-out that is possible. I would never use a bias light in my setup, however if I had a TV that was relatively small, I probably would. But again, if you've calibrated, and have your whites set properly and low enough, they shouldn't be super-bright, and fatigue will be less of an issue.
     
  17. John F. Palacio

    John F. Palacio Supporting Actor

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    While all this discussion about using "bias lights" vs a darkened room for viewing is interesting, it is not the topic that was started by this thread. As a reminder the question was what type of display was easier on the eyes. Then all-of-a-sudden using bias lighting fixed all maladies with all displays!
     
  18. andrew markworthy

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    The next time, as a professor of psychology I'm running Perception 101, I'll invite you along, John.

    What do you think causes the pupil to contract and expand? When your eyes move around trying to focus in the dark, what do you think the lens is doing?

    Dark adaptation is indeed principally the job of the retina (more specifically the rods and cones) but you always need the eye muscles and lens to focus and move the eye around, and trust me, if you have one light source and everything else is in darkness, this causes eye strain over long periods of time.
     
  19. Rich H

    Rich H Second Unit

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    As far as the original question is concerned, I don't know which technology, if any, actually is the easiest on the eyes. People here have made excellent points that there are factors, such as how you view the technology and how it is calibrated, that may well be more important to a comfortable viewing experience than the particular display type itself.

    With that said, I can only report that, personally, I find some plasmas to provide for me the most easy-going, comfortable viewing experience. Projected film, while still the most "romantic" medium, can throw some pretty big artifacts in your face. The general look and beaminess, uneven brightness and the shifting of brightness with viewer movement in rear projected displays is an irritant to me. Same with DLP, and I see the rainbows in that technology.

    My Panasonic plasma is the most comfortable for me (once dialed down from factory settings) because of it's perfectly even illumination that is perfectly stable from any viewing position, it's perfect focus that allows a very clear picture (source material allowing, of course). It's very, very smooth and free of artifacts. It's free of visible flicker, thank goodness. When I view the typical wall-o-crt direct views at an AV store I see a wall of flicker. Peripheral vision picks up motion/flicker better than direct vision, and my peripheral vision flickers like mad in front of those displays. Whereas my plasma does not. All of that makes for the most comfortable, easy and natural type of image I've yet to see.

    And for someone with very good (and quite sensitive) hearing there is one final big bonus: I no longer have to live with the high-pitched squeal of a crt set (15,734 Hertz horizontal scan frequency). I hear that high-pitched ringing from every direct view set and it's an absolute relief to come home to a display that is silent, in that regard.

    As to bias lighting, I like to watch in a darkened environment, theater-style. There is a little light bleed through a window from another room, to keep things from being pitch black. I tried bias lighting behind the display and just couldn't warm up to it at all. I found it a visual distraction (it was a proper bias light) and it detracted from the theater-like, picture surrounded by darkness effect. But, to each his own.

    I suffer no perceptible eye-strain when watching the display in the dark, and guests have found it agreeable as well.
     
  20. Ted Lee

    Ted Lee Lead Actor

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    oh yeah, i almost forgot. some new tv we have at bb has *built in* bias lights that illuminate the wall behind it. kinda cool...
     

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