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Reader Q&A

DIY Treatments for better Outdoor Readability?

After reading several of your articles on I'm interested to know about DIY treatments of some of the Pocket-PC smartphones e.g. E-ten X800. One treatment I have seen is something like this.. Do you have any other suggestions for DIY treatments?
Marty Moloney, Australia

Contributing Technology Editor Geoff Walker answers:

There are two screen protectors listed, one for $8 labeled "anti-reflective" and one for $12 labeled "99% transparency". The anti-reflective one may have a low-grade AR coating on it, reducing the reflectivity of each surface from normal 4% to 2%, for a total transparency of 96% instead of the normal 92%. The $12 may have a high-grade AR coating on it, reducing the reflectivity of each surface from 4% to 0.5%, for a total transparency of 1%. Or it could be 100% marketing bullshit, with no actual anti-reflective treatment at all. Even if it does have a good AR coating on it, AR coatings tend to scratch easily (as you may have noticed if you own any $100+ sunglasses), so adding AR tends to reduce the product's effectiveness as a screen protector.

Reducing the surface reflectivity of the screen protector to 1% (99% transparency) should improve the outdoor readability. However, it's far from a magic bullet. If you use the formula that I give in my articles, you'll see that without increasing the backlight brightness, there's relatively little improvement that can be made in the effective contrast ratio. Plus, the four surfaces of the touch-screen are still reflecting somewhere between 8% and 16%, depending on what kind of treatment the manufacturer used. Putting a screen protector over the touch-screen doesn't have any effect on the inner three surfaces. If the adhesive on the screen protector is very good and the screen protector can be applied without any significant bubbles, then there may be some reduction in the reflectivity of the top surface. However, since the top surface of the touch-screen is very likely to already include some anti-glare (AG) treatment, putting the screen protector on top of it can actually reduce the effectiveness of the AG, making the screen seem to reflect sharper, more distracting reflections.

The bottom line is that a screen protector by itself just can't make a significant difference. Plus, it's expensive and (if AR-coated) subject to scratching. There simply isn't any cheap & easy solution to making a resistive touch-screen more readable outdoors.

Based in Silicon Valley, Geoff Walker is Global Director of Product Management at Elo TouchSystems. Prior, he was a consultant with Walker Mobile, LLC ( Geoff has worked on the engineering and marketing of mobile computers since 1982 at GRiD Systems, Fujitsu Personal Systems (now Fujitsu Computer Systems) and Handspring. In addition to mobile computers, Geoff's areas of particular expertise include displays and digitizers.