Lab tests reveal the sapphire Apple Watch's one weakness

The Apple Watch
The Apple Watch has a choice of displays.

If you're putting down some cash on a new Apple Watch, then the sapphire screen on the more expensive editions obviously offers greater strength and scratch resistance, but there is a catch: ambient light.

Some exhaustive testing by Dr Raymond Soneira at dedicated screen test lab DisplayMate reveals that "screen reflectance" is 74 percent higher on the sapphire models (8.2 percent compared to 4.7 percent). Essentially it reflects back more of its surrounding light and is more difficult to see outdoors.

Soniera has high praise for both displays and this shouldn't necessarily put you off the Apple Watch or Apple Watch Edition - but if you want the best and clearest view of the watch face then the cheapest Apple Watch Sport might in fact be the one to go for.

Plus, given it's supposed to be an 'outdoors-y' sort of watch, being able to see it better in the sunshine makes a degree of sense.

By the numbers

It's worth reading the results of the lab tests in full to see all of the statistics collected on DisplayMate. Contrast also suffers more on sapphire screens as soon as you leave anything other than total blackness.

"In order to increase the use of sapphire for displays, the sapphire industry will need to modify the optical properties of sapphire without significantly affecting its scratch resistance and other mechanical properties," says Soniera. "It can't be done using traditional anti-reflection optical coatings which scratch easily."

The good news is that updated sapphire technology is on the way and should minimise this problem in the future. For the time being, bear these findings in mind when you're out Apple Watch shopping.

David Nield
Freelance Contributor

Dave is a freelance tech journalist who has been writing about gadgets, apps and the web for more than two decades. Based out of Stockport, England, on TechRadar you'll find him covering news, features and reviews, particularly for phones, tablets and wearables. Working to ensure our breaking news coverage is the best in the business over weekends, David also has bylines at Gizmodo, T3, PopSci and a few other places besides, as well as being many years editing the likes of PC Explorer and The Hardware Handbook.