Brightness ratings and contrast ratio make for lovely tech spec reading when you're shopping for a new device. But neither tells you how usable a display will actually be in everyday ambient light situations. So DisplayMate put some of the more popular options to the test.

Surprisingly, neither the Apple iPhone 4 nor the iPad 2 took top honours in their respective categories. The Windows Phone Lumia 900 was actually found to be the best performer under bright ambient light, while the iPhone 4 and Samsung Galaxy S tied for second place.

Which is surprising since the 900 actually uses an AMOLED display which in the past have performed terribly under bright conditions. But Nokia's ClearBlack Display technology, which adds a pair of polarising filters to the mix, has obviously solved that issue.

Overall tablet displays in general were found to perform well below most smartphones, with the Samsung Galaxy Tab 10.1 taking top honours, followed by the iPad 2. And oddly enough, while the new iPad was found to have a better display than the iPad 2, it wasn't included in DisplayMate's testing. So whether or not it was also better than the Samsung Galaxy Tab 10.1 isn't known. What is for certain, though, is that if you plan on using a mobile device outdoors a lot, you'll want to reach for your smartphone instead of your tablet. Or, maybe just pack a Kindle. [DisplayMate]