Screen Protector Caution

Discussion in 'HP Slate' started by Steve S, Jan 14, 2011.

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  1. Steve S

    Steve S Pen Pro - Senior Member Super Moderator

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    UPDATE - February, 2011: To cut right to the bottom line (as of this date), the following screen protectors have been found to be compatible with the N-trig digitizer:

    <> WriteSHIELD (Anti-glare or Clear)
    <> NuShield (DayVue)
    <> Clarivue
    <> Strong Engineering
    <> 3M ClearView

    Of these, NuShield appears to be popular (and has a custom size), but the other brands also have their advocates. Potential buyers are strongly encouraged to read the rest of this thread for important details!

    ORIGINAL POSTING: (I'm going to apologize for this posting right at the outset; this is not the quality of information that I normally try to post.)

    Last night, I tried a screen protector on my slate for the first time. I have used various brands of screen protectors for years, and have many scrap pieces, cut from larger sheets. So, as a quick test, I grabbed one of these scraps and laid it over the top half of the Slate's screen. I was thus able to make an immediate comparison between the light reflections and glare coming from the two parts of the screen.

    As expected, the reflections on the treated half of the screen were noticeably reduced; I usually sit with a lamp behind my right shoulder, and so there's plenty of opportunity for reflections. On the glossy part of the screen the lamp, of course, was clearly visible; on the treated half, the lamp was reduced to a vague and fuzzy outline. Meanwhile, the clarity of the image on the screen was only very slightly compromised by the SP. The pen "feel" was also only slightly different (this SP had a smooth surface finish because it used a true anti-reflection coating rather than relying on surface roughness (matte finish)).

    Here's the problem: I thought the scrap that I picked was WriteSHIELD, but when I tried the pen (to test the feel), I immediately discovered that the digitizer was frozen. That's not consistent with WriteSHIELD performance on my XT. The scrap may also have been NuShield DayVue, but again, DayVue works on my XT2... so I'm forced to say that I don't know what brand of SP this scrap was, and so this is not very useful information, except perhaps to reiterate that:

    1) The right screen protector product can significantly improve screen optical issues that you might find irritating, and...

    2) Not all screen protectors are compatible with the N-trig (or Wacom or Apple) digitizer technologies.

    As soon as I peeled the SP off, the digitizer resumed working, so it does no harm to experiment like this, but I feel bad that I cannot identify the brand under test. I have some SPs that are still in their original packing, and I'll try some more tests over the weekend.
     
    Last edited by a moderator: May 16, 2015
  2. dceggert

    dceggert Owner of a TabletPC Museum Senior Member

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    Steve,
    Excellent investigation!

    When you say that the digitizer was frozen was that for the pen or touch response (or both)?

    I can see where the plastic may inturrupt the field generated from the low-powered pen (or may have faked the digitizer into thinking there was a screen-wide input), but pressure sensitivity, I would assume, would be unaffected. Interesting...
     
  3. Steve S

    Steve S Pen Pro - Senior Member Super Moderator

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    UPDATED

    <<...the digitizer was frozen...for the pen or touch response (or both)?..>>

    ...Both, and for incompatible SPs, that's exactly what you would expect. A couple of things to explain what's going on, here:

    1) The N-trig system is an electro-static system; that means it responds to electric charge or electric fields. Your body has an electric charge, so the digitizer can "sense" your fingertip when you touch it to the screen. The pen generates an electric field which the digitizer senses in a similar way.

    2) Screen protectors are typically made of plastic, or in some instances, glass (more common in photographic applications). Both of these materials are dielectrics, which mean that they aren't conductive. They aren't conductive because these materials trap (immobalize) electrons; this also means that these materials can develop strong localized charges. The most common example is rubbing a balloon. But the presence (or absence) of charge is precisely what capacitive digitizers, like the N-trig (and the new Wacom) digitizers sense. See where this is going? An additional complication is that a "full face" adhesive layer (vice just edge adhesive strips) is highly desirable because it provides the best optical performance. Strong Engineering only uses edge adhesive, which is why I don't like their product. Adhesives have their own nasty dielectric effects and can have a strong detrimental effect on electrostatic sensor performance.

    3) Finally, just to make things really...interesting...anti-reflection (anti-glare) treatments can take a couple of forms. One is to just roughen the surface of the SP so that it doesn't reflect incident light (so-called "first surface reflections"). We know this as a "matte finish." However, there is a much more sophisticated approach which involves optically thin (think: nanometers) layers of either metallic or dielectric materials that perform half-wave cancellation of light. This is the process that is used on camera lenses. Simple versions of this approach are used on some of the best quality SPs, like 3M Vikuiti, but again the metallic and dielectric layers can play Hobb with an electrostatic sensor. Hence the reason why some SPs aren't compatible with some types of digitizers. Obviously, a passive (pressure-sensing) digitizer would be insensitive to these issues...

    I think you probably already understand this, so this explanation is really intended for those who may have questions about this...
     
    Last edited by a moderator: May 16, 2015
  4. TheWerewolf

    TheWerewolf Care for a bite?

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    To be honest, I'd be terrified that the adhesive would damage any conductive layer on the screen...
     
  5. Steve S

    Steve S Pen Pro - Senior Member Super Moderator

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    <<...I'd be terrified that the adhesive would damage any conductive layer on the screen...>>

    ...There is no need to fear this. All of the best known SP makers employ low-tack, low-VOC adhesives. I have SPs that have been in place, literally for years, over screens that have anti-reflection treatments. None of these screens have shown any evidence of any effects, detrimental or otherwise.

    Note that my XT is now 3 years old (WriteSHIELD covered) and my XT2 is 2 years old (NuShield covered). Both screens are still pristine...

    Also note that when it comes time to resell your Slate, because (of course) you are moving up to the Slate XXX, even a single scratch on the screen will have a disproportionately negative effect on the price that you can demand. Even glass screens are susceptible.

    For this reason, I always recommend the use of a screen protector.
     
  6. johnmcd

    johnmcd Scribbler - Standard Member

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    FYI - I just installed a NuShield DayVue protector (iPad version cut down) on my Slate and so far it seems to not hinder any of the touch/inking capabilities. Inking actually feels a little smoother. I can't say for sure how much it'll improve sunlight readability (since it's 9PM right now), but I'll check and post what I find.

    John
     
  7. johnmcd

    johnmcd Scribbler - Standard Member

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    p.s. -1 - it definitely cuts down on fingerprints (almost eliminated them entirely!).

    John
     
  8. Bobo_

    Bobo_ Pen Pal - Newbie

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    Please keep us posted on your findings. I am really interested in its impact on inking and if it helps it any.
     
  9. Steve S

    Steve S Pen Pro - Senior Member Super Moderator

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    As an aid to those seeking information about screen protectors, the following link leads to several SP-related postings at GBM.

    Screen Protector Shootout | GottaBeMobile

    Note that links on this page still appear to work, whereas links within any of the referenced pages appear to be broken. So if you want more information on NuShield, for example, use the link on the page above, not the link within the Screen Protector Shootout Results (second link listed).

    Although the SP Shootout information is now a bit dated, most (all?) of these products are still available. My recollection is that Photodon (I think), WriteSHIELD and NuShield, at a minimum, are compatible with the N-trig digitizer. Although I haven't tried it, my guess is that the iPad SP would also be compatible. Beyond my somewhat hazy memory, the only way to determine compatibility is to 1) Ask the manufacturer (many didn't know), or... 2) Buy one and try it.

    (Although I promised to look at some more screen protectors this past weekend, I wasn't able to. Chores around the house had to take priority...!)
     
  10. Steve S

    Steve S Pen Pro - Senior Member Super Moderator

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    A random thought about iPad screen protectors (there is more than one brand available): it occurred to me that screen protectors optimized for the iPad may not be very durable when subjected to inking with the pen. iPads only feature touch, and your finger is (usually) soft and has a big contact area. By contrast, the nib of the pen is sharp and, relatively speaking, hard. iPad screen protectors may exhibit problems with scratching / scarring because they're likely not optimized for use with a pen...
     
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