March 2014 Issue
Seeing Beyond Polarization
Searching for sunglasses that can view an LCD.
Has Practical Sailor reviewed sunglasses since the 2009 article? The feature we’d really like to have is to be able to read our chartplotter’s screen without removing sunglasses. A review of that particular feature would be extremely helpful.
1989 Gemini 3000
The July 2009 test was our most recent look at polarized sunglasses, and those findings still hold true. The technology hasn’t changed dramatically since then, and the brands that we featured are still among the leaders in the field—although Oakley’s quality has slipped a bit, in our opinion.
We did test the screen-reading feature in our sunglasses report (and we always include it in our chartplotter and multi-function display tests as well). We found that the best LCD screen-readers were the glasses that allowed in the most light (had the highest luminous transmittance). Mirror lenses, which are just another layer to distort light, seemed to make it harder to read the screens. Those with copper lenses—rather than dark, black lenses—fared the best in screen reading. Lenses with about 8- to 14-percent luminous transmittance (no more) were the most versatile in our opinion.
According to Dr. Karl Citek, professor of optometry at Pacific University College, this is a problem because most LCDs—such as those found in smart phones, digital tablets, laptops, handheld GPSs, and chartplotters—are polarized, usually with an oblique polarization axis of 45 or 135 degrees. Standard polarized eyewear for boating has a polarization axis of 90 degrees. As such, it blocks the reflected light from a horizontal road or water surface, which has a polarization axis of 180 degrees. When looking at an LCD through polarized sunglasses, tilt your head (or turn the display) about 45 degrees to one side, and it often will appear black; tilt it the opposite direction, and it often will appear brighter.
Results can vary depending on the sunglasses, the type and model of electronics, and from which side you are viewing the screen. The new iPads, for instance, will turn black in portrait mode, when viewed through most polarized sunglasses. So the only way to know for sure whether you can view your chartplotter through a specific pair of sunglasses is to give them a try. Either buy the glasses and try them on board (provided they have a return policy), or take the electronics shopping with you when possible (smart phones, GPS handheld, etc.). Ideally, you can do this at an outdoor boat show. Be sure not to compromise overall eye protection for the ability to view an LCD; if it comes down to it, just learn to tilt your head (or the device).