Sony has officially launched the Sony Xperia Z4 smartphone in Japan.

It hasn't been very long since the Xperia Z3, Xperia Z3 Compact and Xperia Z3 Tablet Compact were launched, in September last year. The Xperia Z4 smartphone joins the 10-inch Xperia Z4 tablet, which was launched in March at MWC, however there's no sign of an Xperia Z4 Compact as yet.

The Sony Xperia Z4 smartphone is a 5.2-inch full HD screened device. It measures 146mm × 72mm × 6.9mm and weighs in at 144g, so it's both slimmer and lighter than the Z3. However the design language of the metal frame and glass constructed Z4 is very familiar.

Under the hood you have a 64-bit Qualcomm Snapdragon 810 processor and 3GB of RAM with 32GB of built-in storage. Google Android 5.0 is the mobile OS installed. A 2930mAh battery is said to have the stamina to provide 17 continuous hours of 3G talk time.

Sony mobiles have some imaging pedigree and the camera section of official specs table takes up over a third of the height of the entire table. However the Z4's main camera is unchanged from the Z3, it uses a 20.7 million pixel back-illuminated stacked 1/2.3-inch CMOS sensor Exmor RS for mobile. The selfie camera is improved though, this time you have a 25mm wide-angle 5.1 million pixel back-illuminated CMOS sensor Exmor R for mobile equipped camera unit.

To complement the visuals Sony has implemented support for LDAC High Quality Wireless Listening. This is supposed to offer very high quality wireless audio via Bluetooth 4.1 as it relies upon three times more audio data being transmitted

As Xperia fans might expect, the new Z4 offers both IPX5 / IPX8 equivalent waterproofing and IP6X equivalent of dustproofing. Sony has implemented a convenient capless waterproof USB port to match the waterproof headphone jack.

Sony will offer up Xperia Z4 smartphones in White, Black, Copper, Aqua Green and it is also producing matching smart-covers with glance windows. The other accessory announced is a desktop charger. Both accessory ranges are said to be coming this summer. The phone itself will be exhibited at the Ginza Tokyo Sony showrooms from 22nd April.