Why You Can Trust CNET Pentax Optio RZ18 review: Pentax Optio RZ18
At £160 the Pentax Optio RZ18 superzoom's sharp, colourful pictures are far better than its price and build quality might lead you to expect.
Ultra-compact, ultra-zoom is how Pentax describes the RZ18. While we're not so sure about the ultra-compact bit -- it's larger than the Canon IXUS 230 HS and Casio Exilim ZS10, roughly matching the size of a box of cigarettes -- we're right on board with the latter.
Pentax Optio RZ18
The Good
The Bad
The Bottom Line
Packing one of the longest zooms currently available on a pocketable camera, at 18x zoom, the RZ18 tops much of the competition. It is keenly priced at £160.
Build and design
Build quality is good but not great. The RZ18's body is entirely swathed in cheap-feeling black, white or orange plastic and there's clearly some space behind the finger grip. It flexes slightly when pressed and sounds hollow when tapped.
The flash is positioned directly above this rather than to the right of the lens, which is a shame as your fingers can easily get in the way -- as ours did.
Shot-to-shot time is a slow 5 seconds when using the flash and around 2 seconds when it's switched off. Both of these times are too slow for our liking.
Around the back, the buttons are clicky and tacky. They're well laid out and easy enough to use, but they're unrefined and unresponsive. They don't sit well on a camera that costs upwards of £160. The screen has a slightly coarse grain and when framing subjects that aren't brilliantly lit -- under regular indoor lighting, for example -- there's some noise in the on-screen picture. The menus look dated too.
Stills performance
What really matters though is how it performs. Here it did rather well. We have no complaints where handling is concerned. There's an 18x zoom, equivalent to 25-450mm in a regular 35mm camera. It's both quick to find its position and fast to focus when you half-press the shutter release. It's not overly noisy, so you can use it fairly discreetly.
We set the RZ18 to its maximum 16-megapixel resolution, using auto picture mode so that it could choose the best settings throughout our tests.
It consistently impressed us with accurate colours and sharp images at all levels of zoom. The RZ18 did a good job of working with lower levels of available light, keeping its sensitivity at the bottom end of its ISO 80 to ISO 6,400 range.
Its macro mode, which tops out at 4cm, is quick to get a fix and renders plenty of detail. Even with a fairly narrow palette, such as the teasel head below, it picks out not only the spines but the smaller teeth on each one against the darker interior; it does this while throwing the background out of focus, thanks to its self-selected aperture of f/3.5 -- its maximum at full wide-angle. When zoomed to 18x, the maximum aperture narrows to f/5.9.
The RZ18 consistently impressed us with the sharpness and clarity of its results, particularly when shooting complex scenes. The shot below of a tree full of red leaves has a lot of fine detail in the foliage, with a definite sweet spot in the centre of the frame where the focus is particularly sharp. The areas behind and ahead of this are both slightly blurred due to the fairly wide aperture of f/4.4, drawing the eye in to the centre of the frame.
However, where it encountered strong contrasts, its performance was less impressive. The RZ18 initially fired the flash when shooting the image of a tree below, where we were looking directly up into the canopy. This was despite the fact that, as can be seen from the image, there was plenty of light in the scene. It was actually the second time we'd tried to manually suppress the flash.
Surprisingly, when the flash was switched off, the RZ18 actually knocked down its sensitivity from ISO 600 to ISO 500, without introducing a great deal of noise; it slowed the shutter slightly (from 1/60 to 1/50-second) to compensate. The full range of shutter speeds stretches from 1/2,000-second to an unimpressive 1/4-second in all but night scene mode, which extends it to a more respectable -- although still conservative -- 4 seconds.
The wood is well rendered and there's plenty of detail in the pine needles. But where these meet the areas of overcast sky visible between the branches, we noticed that the image suffered from a loss of detail. This had also been evident in the version of this shot captured while using the flash.
This loss of detail, where finer parts of an image passed in front of an overcast background, occurred frequently during our outdoor tests as the light encroached on the darker elements.
The same effect can be seen in areas where the light meets a solid block of a darker tone -- for example, where it encroaches on the underside of the arches in the railway bridge below. Sensitivity was automatically pinned down at ISO 80 -- as low as it could go -- yet there was still too much incoming light to preserve the sharp edge.
The camera's underlying firmware is flexible, allowing you to tweak sharpness, saturation and contrast. It's also intelligent and can fix on up to 32 faces in a frame. The pet mode even lets you give priority to three pre-registered pet faces, which it will recognise and focus on in preference to other unrecognised cats and dogs.
Fortunately there were no pets involved in our still-life test -- just a collection of everyday objects with different surface textures and colours. Here, the RZ18 did a great job under studio lighting, producing a very balanced shot with accurate colours and extremely sharp text on a printed page.
There was a fall-off in the focus towards the back of the scene as it self-selected macro mode and set its aperture to f/3.7. But with sensitivity pinned at ISO 80, the focused parts of the image were crisp and free from noise or grain.
Switching off the studio lights and relying on the ambient light of our surroundings introduced a considerable level of grain as the RZ18 hiked its sensitivity to ISO 800 -- one of the highest self-selected settings we have seen in this test. The colours remained accurate towards the front and centre of the frame, if a little warm. However, there was a significant blue/red cast towards the back, where the actual colour should have been white.
We performed the test a third time using the flash, which cast strong shadows. Although it allowed the camera to dial back the sensitivity by 50 per cent, thus reducing a lot of the grain, it still didn't manage to reclaim the white that had been lost from our background.
Movie mode
Movie mode is found in the scenes menu, alongside portrait, fireworks, sunset and so on. At its highest resolution it records at 1,280x720 pixels and 30 frames per second.
The results here were more mixed than they had been when shooting stills. Cooler scenes dominated by blue tones were grey and washed out, yet more vibrant shots such as autumn leaves were beautifully rendered with vibrant colours and plenty of detail.
More concerning was the fact that the optical zoom is locked off when you're shooting video. Presumably this is so that the soundtrack doesn't pick up the sound of the servos shifting the barrel. That's a compromise that we've seen on other cameras, but we'd still like the optical option to be there; we'd prefer to choose whether we'd accept some noise on the audio track or not.
The 7.2x digital zoom is still available, but pushing this to its fullest extent is inadvisable as it seriously degrades the image. Our advice would be to set the optical zoom before you start recording and then leave the zoom rocker well alone.
Conclusion
The RZ18 is, at its heart, a great little camera. It has an impressive zoom and a sensor that knows how to handle 16 megapixels without producing noisy results. Even as sensitivity crept up to around ISO 500, at which point we would expect to see grain, the results were clean and full of detail.
We were concerned that the lens occasionally had trouble focusing all of the incoming light accurately; fine details would sometimes be lost if they were shot against a particularly bright background that would quickly envelop them. In less challenging lighting situations, the RZ18 produced a great set of results with sharp detail and accurate, vibrant colours.
It's a shame then that Pentax has chosen to dress up what is a competent piece of kit in such a plasticky chassis. It looks smart enough but it feels cheap and tacky -- much more so than its price would suggest. If you're happy to ignore this, and want to buy it for its performance rather than its build, you'll have a great little snapper on your hands.