A phone for all weather

If ever there was a time to have a waterproof smartphone, the past week was it.

Motorists are counting the cost of water- and hail-damaged cars. Property owners are getting quotes to replace collapsed walls and tornado-stripped roofs.

Many, no doubt, are also submitting insurance claims for rain-drenched cellphones, a fair number cursing the clause excluding water damage they hadn’t noticed in the fine print.

It was at times like these I really wished I still had that Sony Xperia Z5 Premium review unit.

The Japanese tech company deserves a lot of credit for introducing the concept of water resistant smartphones several years ago, with multiple generations of it Xperia Z line of flagship devices impervious to the wet stuff.

Other manufacturers have followed Sony’s lead, most notably Samsung with its S7 and S7 Edge handsets and there are persistent rumours its new Note 7, due to be launched globally on August 2, will also be waterproof.

After the events of the past week, water resistance has moved closer to the top of my list of characteristics my ideal smartphone must possess. But if the few weeks I spent with the Z5 Premium taught me anything, it’s just how useful this feature is even in sunny weather.

Before I get to that, though, a quick description of the device. As the name suggests, it’s the best-specced - and at 5.5 inches the biggest - of the Z5 line line which also includes the 5.2-inch Z5 and 4.6-inch Z5 Compact.

Constructed largely of glass both front and back, with aluminium edging, the Z5 Premium is a handsome if pretty hefty piece of kit, its slab-like dimensions slightly mitigated by the subtly rounded corners, which are also reinforced to give it some protection against minor drops and bumps.

Anyone familiar with previous incarnations of the Xperia Z line will be relieved to hear Sony’s refined its waterproofing technology to the extent that it’s now done away with all, bar one, of those fiddly flaps that used to cover vulnerable points like the charging and earphone slots and were prone to snap off with repeated use. The one remaining flap is a lot easier to use and, as it covers the nano SIM and micro SD card slot, you won’t need to open it much anyway.

If you like your smartphones with big, bright screens, you’ll love the Z5 Premium. With the launch of this device late last year, Sony became the first manufacturer to release a smartphone with a screen resolution of 4K - that’s 2160x3840 pixels, which works out to an astonishing 806 pixels per inch.

It’s undoubtledly a feast for the eyes and watching videos and playing high-end video games was a joy, both of which I was able to enjoy without worry in the bath thanks to the Z5’s dunkability.

Most of the time, however, you won’t be using the full capability of the display because to gain access to the 4K resolution you need to view high-quality video or photos within Sony’s photos or video apps.

The downside of 4K displays is that they need lots of processing and battery power. Fortunately, the Z5 Premium has plenty of both - a quad-core 1.5 GHz Cortex-A53 and quad-core 2.0 GHz Cortex-A57 processor, 3GB of RAM and a 3430 mAh battery.

I never experienced any performance issues, but battery drain was definitely a factor, with the Z5 Premium only just squeaking through a full day of medium use most days. If you’re a heavy user you’ll definitely want take the charger with you to work as it uses one of the new Type C connectors, which means you’re unlikely to be able to use a friend or colleague’s charger to top up your phone.

One of the strong points of the Xperia Z line has always been its cameras and the Z5 Premium is no exception. The 23 megapixel front camera took excellent pictures in a variety a lighting conditions. Such a big, bright screen really comes into its own when framing still shots and videos as well as viewing the images and footage afterwards.

Sony strongly recommends against immersion in corrosive salt water, so do rinse this and any other waterproof phone in fresh water after any exposure.

Follow Alan Cooper on Twitter @alanqcooper.