The latest mid-range smartphone from Asus packs big cameras and an even bigger battery.

The ZenFone Zoom S - which is branded as the ZenFone 3 Zoom in other markets - has dual-camera lenses and a whopping 5,000mAh battery in a relatively slim 7.9mm body. These are quite impressive specs to have in a mid-range phone.

The phone itself does not stand out or look too fancy. It has a simple, clean metal body and a wide 5.5-inch screen.

In fact, it can be mistaken for an iPhone 7 Plus at first glance, save for the lack of a centre home button.

Even the lens bump on the phone's back, which houses the phone's dual-camera lenses, is identical to that of the iPhone.

This isn't an accident, though, as Asus released a comparison video between the two phones earlier this month, and is clearly setting up the Zoom S to be the David to the iPhone's Goliath.

Unfortunately, the Zoom S, while putting up a valiant fight, still can't trump Apple's offering, but not for lack of trying.

Like last year's original ZenFone Zoom, this phone retains long- range zoom capabilities, with up to 2.3x optical zoom and a ridiculous 12x digital zoom.

On paper, the 12-megapixel sensor with f/1.7 aperture sounds impressive. Pair it with a 59mm, f/2.6 telephoto lens and it sounds like it should put up quite a challenge to other dual-lens phones in the market, such as the iPhone 7 Plus.

And the zoom on this device is impressive. While some level of grain and loss of detail is to be expected, I found that the Zoom S retained enough detail, such as rough paint cracks on the wall, when zoomed in.

Image quality is great when shooting outdoors with natural lighting, providing pictures with good contrast and detail. I discovered that the colours tend to lean a bit on the warm side,with slightly exaggerated reds and oranges.

But when used indoors, in either low light or harsh fluorescent lighting, the Zoom S starts to struggle - particularly with exposure.

While shots taken are still generally usable, it takes some adjustment to get the lighting correct under artificial conditions.

But the exposure settings also go haywire when confronted with a bright object, like a computer screen in the foreground, which the phone compensates for by darkening the background too much.

This can be mitigated somewhat by switching to manual mode and fiddling with settings. But, to the majority of users who want a fuss-free, convenient auto photo- taking experience, that will be too much of an unnecessary hassle.

The 1080p, Full HD screen is a standard offering on most phones today, and the one on the Zoom S holds its weight in displaying bright, colourful images and video.

Its 5,000mAh battery is nothing to sneeze at, as it is huge enough that the phone can double as a battery pack for a spare or friend's phone running out of juice.

On the software front, the Zoom S ships with a modified version of Android 6.0.

An update to the latest Android 7.0 operating system is on the cards - Asus says this will be released within the year.

It is, however, a version of Android skinned with Asus' own Zen UI. I'm not a fan of the UI, with its garishly large and colourful settings icons that come in searing shades of bubblegum blue and neon green.

•Verdict: The ZenFone S doesn't quite match up to be the iPhone killer it is made out to be, but, nonetheless, is a decent mid-range phone, though its price is near-flagship level.