A 30x optical zoom to use with your smartphone sounds like a good idea in theory, but in practice it can be frustrating. Like: 30x optical zoom; NFC and Wi-Fi connectivity Dislike: No screen; Relies on smart device battery life; Connectivity issuesWhen Sony first introduced its concept for a lens camera, it seemed like an interesting solution to the problem of declining compact camera sales.It looks like a giant add-on lens for your smartphone, but it's actually a completecamera. The only role your smartphone plays is as an interface for controlling the camera, viewing your photos and, ofcourse, sharing them via social media ifyou like.*.Buy Sony DSC-QX30 Digital Camera with Wi-Fi and NFC (20.4MP, 30x Optical Zoom) at Amazon UK for £249.00At the time Sony introduced theQX10, which had a sensor of a similar size to astandard compact camera, and theQX1, which featured the same one-inch sensor as in theRX1premium compact camera.We can assume that the concept has proved reasonably successful for Sony, as it has now introduced two further models. The QX30 has a 30x optical zoom, as well as a sensor the size of that in a compact camera. The other new model, the Sony QX1, features a larger, APS-C sized sensor and interchangeable lenses.*.Sensor size explainedThe QX30's sensor is a 20.4 million pixel, 1/2.3 inch CMOS device. That 30xoptical zoom gives an equivalent 35mmfocal length of 24-750mm, which gives your smartphone (or tablet) much more flexibility than its built-in single focal length device.Also featured is a Bionz X processor, the same chip as found in the company's top of the line cameras, including theA7full-frame compact system camera. This should mean that it has fast processing speeds and is capable of producing low-noise imagesin low-light shooting scenarios, though small sensors like this are more noisy in the first place.In order to control the camera, and indeed see what image you're composing, you'll need to rely on Sony's SmartMemories mobile app, which is available for both iOS and Android as a free download. Within this app, you can use fully automatic modes, as well as aperture priority, shutter priority and Program Auto mode.Competition for the QX30 is hard to pinpoint as these types of cameras are still pretty unusual within the marketplace, but it could be argued that cameras such as theSony HX60and thePanasonic TZ60, which also feature30x optical zooms are the obvious choice.Build quality and handlingWith its 30x optical zoom, the QX30 is significantly larger than the QX10. That said, when the lens is collapsed, the overall size of the camera isn't too large. The shape of it means, though that, unlike something like the HX60 superzoom camera, it's unlikely you'll be able to fit it into a jeans pocket.There are two main ways to use the camera - you can attach it to your smartphone via the extendable clip on the back of the camera, or you can use it entirely separately, such as by attaching it to a tripod via the thread on the bottom of the camera and control it from a different position – useful if you want to take a group/self portrait or shoot from an awkward angle.As most of the control of the camera takes place via the PlayMemories app, there are just a few buttons on the QX30itself. Aside from the on/off button, you'll only find a shutter release and a zoom switch. Both of these aspects canalso be controlled from the app if you prefer, or if you're controlling the camera from some distance.In order to connect the camera to your smartphone or tablet, you can use either NFC if you have a compatible device, or Wi-Fi if you don't. Hooking upthe two devices via NFC is much easier as it requires only a simple tap together of the two - the first time you connect, ifyou don't have the PlayMemories app you'll be prompted to download it. Fromthere on in, the app should load automatically when you tap the two devices together.Although in theory the idea of NFC is very good, there were several occasions during the test (when using aSony Xperia Z2) when the camera refused to connect, and I had to power the phone on and off to get it to work. This can be very frustrating when you want to take a quick photo.Connecting via Wi-Fi seems to be a little more reliable, but you do of course need to set it up in the first place - you'llfind the password located under the battery flap, but once you've connected once your phone should remember it.Although there's not much in the way ofdisplay lag when using the camera via either connection method, the shot-to-shot time is quite slow, which can be another frustrating element of using thecamera. Usually, you'll press the shutterrelease icon on the app, and a loading icon will be displayed, three to four seconds later, the app will show a 'Fetching' bar, and a second or so later, the camera will be ready again to use – it's not exactly the speedy experience you'll get with a normal camera.Going back to the app interface, if you'reshooting in aperture priority or shutter priority, along the bottom of the screen, you'll see various parameters you can change, such as aperture, exposure compensation or ISO (sensitivity). Simply tap the setting you want to change, then swipe with your finger along a virtual dial to change the setting. In order to set the autofocus point, simply tap the point on the screenyou wish to use as the focus point. You can also set it to fire off the shutter release with the tap of the screen.As is stands, you still can't use the camera with other apps as a native camera, such as Instagram, which means you'll need to take a photo with it that you later edit in such apps.