Flicker-free tablets

Discussion in 'Hardware' started by Jamon, Oct 22, 2014.

  1. Jamon

    Jamon Scribbler - Standard Member

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    Please share info about which pen-tablets have screen flicker.

    Quick test:
    1. Put phone camera against white part of tablet screen
    2. Lower tablet brightness while looking at phone camera app
    3. Do you see scrolling lines? Reply with the answer


    :mad: Aspire Switch 11 V >
    :mad: Asus Transformer Book Chi (S) flickers in that video >
    :) :mad: Asus VivoTab Note 8 M80TA (S) no PWM above 25%, then 202Hz >
    :) Dell Venue 8 Pro (S) no PWM until around min brightness, then not full on/off at 24 kHz >
    :) :mad: Dell Venue 11 Pro (S) PWM below max brightness at 5 kHz >
    :mad: Dell Venue 11 Pro 7140 (S) video shows flickering at low brightness >
    :mad: Fujitsu Lifebook T725 video shows flicker >
    :) Fujitsu Lifebook T902 stormi says flicker-free >
    :mad: ? Fujitsu Lifebook T935 looks unstable in this video >
    :mad: Fujitsu Stylistic Q555 (S) flickers in that video >
    :)? Fujitsu Stylistic Q584 (S) see no flicker in videos, but they might be max brightness
    ? Fujitsu Stylistic Q775
    ? HP Pro 612 x2 G1
    :mad: HP Envy Note 8
    video shows flicker >
    :mad: HP Spectre x360 video shows flicker >
    :mad: Lenovo ThinkPad Tablet (S) flickers bad below max brightness
    :mad: Lenovo ThinkPad Tablet 2 (S) flickers in video
    :) Lenovo ThinkPad Tablet 10 (S) no flicker in videos, 2 people claim none in cam test
    :mad: Lenovo ThinkPad Helix 1 flickers bad in that video >
    :mad: Lenovo ThinkPad Helix 2 (S) maybe at low brightness?; Thomas says none; I see scroll lines in vid; VMax confirmed PWM > > >
    :mad: Lenovo ThinkPad Yoga 2 12 flickers in video > >
    :)? Lenovo ThinkPad Yoga 2 14 see no flicker in videos yet

    :)? Lenovo ThinkPad Yoga 2 15 see no flicker in videos yet

    :)? Lenovo Yoga Tablet 2 AnyPen (S) no flicker in video > >
    :) :mad: Microsoft Surface Pro 3 200Hz; flicker-free above 55% >
    :) :mad: Microsoft Surface 3 PWM in lower brightness >
    :mad: Motion Computing R12 see waves in video >
    :mad: Pipo W5 video shows PWM >
    :) Samsung Galaxy Note 8 (S) >
    :) Samsung Galaxy Note 10.1 2014 Edition (S) >
    :) Samsung Galaxy Note Pro 12.2 (S) >
    :) Samsung Galaxy Note 1 (S) none even at lowest brightness
    :mad: Samsung Galaxy Note 4 (S) 240Hz; partial flicker even at 100% >
    :mad: Toshiba Encore 2 Write (S) Jag posted a video that shows screen waves >
    :mad: Toshiba Portégé Z20t (S) flickers in that video > >
    :mad: Wacom Cintiq Companion 2 flickers in that video >


    No pen

    :) Apple iPad >
    :)? Apple iPad 2
    :mad:? Apple iPad 3 >
    :) Apple iPad 4 Rob says good; 16 kHz with smoothing filter >
    :) Apple iPad Air none >
    :) Apple iPad Air 2 >
    :) Apple iPad Mini Retina none >
    :)? Apple iPad Mini 2
    :) Apple iPad Mini 3 >
    :mad: :) Lenovo Yoga 2 Pro 1 kHz PWM at all brightness >



    :) No flicker
    :mad: Flicker
    (S) Silent means no fan and solid state drive
     
    Last edited: Dec 29, 2015
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  2. chilis3

    chilis3 Pen Pal - Newbie

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    I have been looking for something like this and hope that other people might pick it up. I am looking for a Windows 8 tablet with flicker free that is cheaper than a Surface. That being said, I need to go test a surface 3 at that brightness or higher. I haven't found a windows tablet that was acceptable at that level.
     
  3. stoneseeker

    stoneseeker Animator and Art Director Senior Member

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    My NotePro 12.2 flickers in certain apps more noticeably even with adaptive brightness turned off. So I would change that one to a :(

    It's not often and doesn't seem connected to pen use, but its there and weirds me out when I see the brightness changing like that. Do we know what causes this? Are you turning off adaptive brightness on all these devices? Has anyone gotten adaptive brightness to work properly for them? I find it constantly adjusting and bugging the heck out of me. I wish there was a sensitivity setting so you could have it adjust more smoothly and less frequently to the slightest shadow of a hand over the sensor.
     
  4. thatcomicsguy

    thatcomicsguy Scribbler - Standard Member Senior Member

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    The moment you turn down the brightness of your LED monitor, it's going to start to flicker.

    Read on to learn why that is...

    I generally prefer to avoid flickering lights. -Anything in the old school fluorescent tube kind of range, (60 hertz, on/offs per second.) It does something to the brain, lulling our minds into a trance-like cognitive state.

    Back when I was studying this stuff deeply, I ran across this great video presentation, where they plugged test subjects into an EEG machine, to measure brain wave patterns. Anybody looking at one of those old TV monitors slips quickly into a sort of dream-state, where the brain wave patterns switch from regular waking patterns to an alpha brain wave form. Essentially, a light hypnotic state:


    "Psychophysiologist Thomas Mulholland found that after just 30 seconds of watching television the brain begins to produce alpha waves, which indicates torpid (almost comatose) [slow] rates of activity. Alpha brain waves are associated with unfocused, overly receptive states of consciousness. A high frequency alpha waves [sic] does not occur normally when the eyes are open. In fact, Mulholland’s research implies that watching television is neurologically analogous to staring at a blank wall.

    [...] the goal of hypnotists is to induce slow brain wave states. Alpha waves are present during the 'light hypnotic' state used by hypno-therapists for suggestion therapy."

    http://www.causeof.org/brainwaves.htm



    One interesting test they performed was to present subjects with a math problem to do in their heads, one on a sheet of paper, and the other, the same problem, on a TV screen. The subjects would do the math and reach the same solutions, but their brains were operating in very different ways depending on what they were looking at. The wave forms for the TV group were all 'asleep' as far as the EEG machine readings were concerned.

    Flickering lights also affect metabolism; you digest food and burn fuel differently when you're staring at a flickering light source. And of course, light flicker affects cognition; it's why it was so difficult to remember the TV commercial viewed twenty seconds earlier. The messages transmitted from TV screens would go in deep and we wouldn't be aware of it happening because we were essentially sleeping through the process. Since the advent of the TV in the 50's, the entire world was subjecting itself to an experiment in hypnotic suggestion.

    Yikes!

    So I was really happy when LED and LCD technology came along and changed how screens work.

    Though, interestingly, the hypnosis thing continues to affect us. Those giant Plasma Screen TVs are not a solution; They still flicker at something like 240 hertz, which is low enough to still mess with your head.

    But the cold cathode tube displays, (which powered last decade's LCD monitors), flicker at something like 10,000 to 30,000 times per second, which doesn't to my knowledge have the same effect on brain wave patterns. It's too fast to matter, (to the eyes, anyway.) So that's a step in the right direction.

    But LED backlights are really interesting. LEDs give off a constant light! No flickering at all. So that should be perfect, right?

    Except. . .

    It's not.

    There are two ways to change the brightness of an LED.

    One is to lower the current flowing through it. Less current = less brightness. The problem is, the current-to-brightness ratio is not a linear curve, and it's a really steep and sensitive curve at that. (Where very subtle differences in current can make a big difference in brightness). So it's very difficult to regulate smoothly.

    The other way, (the way they do it in all these tablets), is through a system called, "Pulse Width Modulation" (PWM).

    Here's how one electronics writer describes it:

    "If, over a short duration of time, we turn the LED on for 50% and off for 50%, the LED will appear half as bright since the total light output over the time duration is only half as much as 100% on. The important factor here is the ‘duration’, if we turn the light on and off too slowly the viewer will see the flashing of the LED not a constant light output which appears dimmer. [...] The minimum speed of an LED oscillating which can be seen by the human eye varies from person to person. However, for the purposes of this article, we will use a minimum speed of 50Hz, or 50 times per second (the same speed as used by European televisions).

    http://www.waitingforfriday.com/index.php/Controlling_LED_brightness_using_PWM

    So.., what this means is that the moment you turn down the brightness of your LED screen, you are turning on the flicker, and the preferred flicker rate used by manufacturers is right smack in the middle of what I affectionately term the, "Mind-Control Range" of around 50-60 Hz.

    So... nope.

    -They've taken the one modern and efficient lighting technology, the awesome white LED, which is capable of delivering 'clean' light, and they've turned it into another mind toxin delivery system.

    Fortunately, there's something you can do about it, and it's pretty simple: Don't turn down the brightness of your LED screen. (This means, don't turn it down via software, graphics card or with the little buttons on the display itself. Disable auto-brightness features and never tick the box which allows a program to adjust your monitor characteristics. -If that's a possibility in Windows 8. In Windows 7, this can be fully user-controlled).

    If you need to adjust the screen brightness, it's better to turn up the ambient light of the room you're in and let your irises do the light modulation for you.

    Who knew, eh?

    Well, now anybody who has read this post knows.
     
    Last edited: Mar 18, 2016
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  5. stoneseeker

    stoneseeker Animator and Art Director Senior Member

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    Wait, I think I'm confused. I thought we were talking about an irregular flicker, not a constant light frequency.
    The kind of frequency I am referring to noticing is never seen on my T902. Its an occasional brightness adjustment that happens on the Note, almost like light bleed happening in varying degrees and then disappearing. As though someone turned on adaptive brightness for a splite second, it wigged out, and then went back to normal. Anyone else see this happen??
     
  6. crazypicard

    crazypicard Pen Pal - Newbie

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    I wish someone would make a flicker free guide for cell phones. I have not owned a cell phone for 7 years thanks to PWM. I'm not even sure there is a cell phone on the planet that doesn't flicker. I have two options at this point, plasma T.V.'s and LED flicker free monitors. I found one company that made 2 gaming laptops that were flicker free but the price tag was way too high. Anything that flickers gives me crazy migraines that go on for days. I would love a cell phone or small tablet that didn't flicker. I would be hesitant to buy one that didn't say flicker free. Just in case I buy it and can't use it. Great list, I'm interested in the Galaxy Note 8 because it's cheap. The Galaxy Not 8 has an IPS screen. I wonder if that has something to do with the no flickering?
     
  7. Jamon

    Jamon Scribbler - Standard Member

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    The original Samsung Galaxy Note is a flicker-free phone. I'm only including devices with a pen in this list. But you can check ixbt.com for graphs of PWM in phones. Look for the ones with 3 flat lines.

    Like this:

    [​IMG]

    Not like this:

    [​IMG]
     
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  8. crazypicard

    crazypicard Pen Pal - Newbie

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    Thanks for all this Info, I was on the site. Tons of Information on everything you need to know about phones. I didn't see the graphs for checking the PWM on the phones. Is there something you have to type in the search to find it?
     
  9. Jamon

    Jamon Scribbler - Standard Member

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    Disappointing that the Wacom Cintiq Companion 2, Cintiq 27QHD, Toshiba Portege Z20t, and Asus Transformer Book Chi use PWM for dimming the backlight.
     
  10. Jamon

    Jamon Scribbler - Standard Member

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    If you do a simple 1-minute PWM test, like view the screen through your digital camera or smartphone, and slide the brightness on the tablet from maximum to minimum, I'll PayPal you $1 for each tablet with pen input not previously tested.
    If you do a 5-minute test of snapping a pic with horizontal movement of a vertical white line on black background at minimum brightness, and uploading with EXIF containing the shutter speed, it's $5.
    Or for free, just set minimum brightness, open a blank white page, and wave your fingers in front to look for strobe trails. Compare that to maximum brightness, which usually has no PWM.
     
    Last edited: Feb 11, 2015
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