Available in a range of hues, there's much to like about the 12.4-megapixel Pentax K-x, an entry-level digital SLR with some sophisticated features that you don't normally see in its price class, including 720p video-capture capability. Pentax has a history of releasing aggressively priced dSLRs, and the K-x is no exception. It's available for about £480 for the body only, £580 with an 18-55mm kit lens, and £700 with an 18-55mm lens and 55-300mm lens.
The K-x feels solid and well made, and it's slightly more compact than most of its competitors. But it runs on four AA batteries, which makes it heavier than some rivals.
One of the camera's highlights, as well as its frustrations, is the viewfinder, which it inherits from its predecessors. On the one hand, it's bigger, with slightly better coverage and more magnification than you get with most consumer models. On the other hand, although there are basic framing lines, the camera, bewilderingly, doesn't display the autofocus areas.
This is annoying for a couple of reasons. For one, if you shoot in complete autofocus, you have no idea which points the camera has selected in order to know if you need to switch out of that mode. If you use single-point AF, there's no reminder if you've moved it (without routinely looking at the LCD for confirmation). You do get an AF area indicator in live view, with a couple of good magnification options for manual focusing.
You can program Pentax's signature green button to reset the camera, choose the image settings, show a depth-of-field preview in the viewfinder, apply an effects filter, reset the autofocus point to centre, or override the file-format settings. We really like Pentax's file-override capabilities. You can define a behaviour for any given scenario: the function depends upon whether the camera is set for JPEG, raw only, or raw and JPEG, and you can define the override you want for each, as well as whether it's sticky or cancels after one shot.
Although it lacks many of the explanations and hand-holding features that some other entry-level models provide, the K-x's operation is relatively straightforward, incorporating many familiar conventions that point-and-shoot users will be familiar with. Some aspects make much more sense than other implementations we've seen. For instance, the ISO screen lets you choose auto or a fixed value, as well as displaying the auto range you can choose from -- the latter is usually buried in a menu somewhere.
There's plenty of information on the status screen, but it provides an easy-to-scan display of most of your current settings. An 'info' button pulls up an interactive control panel that provides access to almost all the settings: image controls (saturation, hue, high/low key, contrast and sharpness), cross processing, special effects, automatic high dynamic range, shake reduction, metering, autofocus mode, metering, highlight correction, shadow correction, file format, resolution, compression, distortion correction and lateral chromatic aberration adjustment.
The K-x includes a couple of interesting features. In addition to the traditional program, aperture-priority, shutter-priority and manual exposure modes, Pentax offers a 'sensitivity-priority' option, which automatically adjusts the shutter speed and aperture as you scroll through a user-determined range of ISO sensitivity values. It's a good alternative to the trial-and-error approach to finding the lowest ISO sensitivity that will deliver a desired exposure. There are also other veteran Pentax features like 'catch-in focus' and the effects filter introduced with the K-7.
An auto high-dynamic-range feature combines three sequential exposure-bracketed shots into a single JPEG. But, unlike competing implementations from Sony, for example, it's not really effective as a simple way of producing better low-light images -- shake reduction is automatically turned off and the camera doesn't seem to do any advanced alignment of the images. Even at a fast shutter speed, there's significant camera shake, so you can only use it on a tripod.
For the most part, the K-x is very fast. It takes 0.7 seconds to turn on and shoot, which is quite slow but not too bad. The time taken to focus and shoot in good light is a zippy 0.3 seconds, increasing to only 0.5 seconds in low light. Two sequential JPEGs run at 0.4 seconds, with a slight bump to 0.6 seconds for raw. The camera's 1.2-second shot-to-shot time with flash is the only real cloud in the K-x's speed sky, although Sony models generally perform worse in this regard. The typical continuous-shooting speed is a solid 4.2 frames per second.
Unfortunately, the K-x's image stabilisation is something of a letdown. For whatever reason -- excessive mirror slap vibration, a stiff shutter or simply a poor implementation -- we had plenty more photos with camera shake, even at high shutter speeds and modest focal lengths, than we're used to seeing these days. Furthermore, the LCD display is fairly coarse, which makes it hard to accurately judge if photos are sharp enough. It's also difficult to see the display in direct sunlight. And, as is typical for all but Sony's dSLRs, the live-view autofocus is pretty slow.
Turn the noise down
The K-x is capable of shooting excellent photos. It has a very good noise profile for its class, including well-balanced noise reduction in JPEG files. You can start to see some degradation of detail in shadow areas at ISO 800, but we found the images quite acceptable even as high as ISO 1,600. By ISO 3,200, the decrease in detail becomes obvious.
Pentax rightfully considers ISO 12,800 (and ISO 100) an expanded mode, although we'd probably add ISO 6,400 to that as well. Although there's still usable detail at ISO 3,200, noise and noise-reduction artefacts are obvious by ISO 6,400, even when scaled down.
We wouldn't recommend using ISO 12,800 as a rule, but it's actually pretty good. You lose much of the shadow detail and there's obvious blotchiness, but photos retains good saturation and are more than acceptable for Web use at small sizes. The K-x maintains good colour consistency across all ISO sensitivity levels.
Pentax's 18-55mm kit lens doesn't display much distortion, and the body's optional internal distortion correction does a pretty good job of fixing what little there is. On the other hand, the lateral chromatic-aberration adjustment option didn't seem to fix much at all. Overall, it's a generally good kit lens.
Although the K-x's default 'bright' image setting produces a slight colour shift over neutral, despite ostensibly bumping up only the contrast and sharpness, it's not nearly as severe a shift as in Sony's comparable models. Unlike Sony, Pentax also provides a 'natural' option. Pentax's automatic white balance normally tends to be on the cool side, however, which results in an overall colour cast.
The K-x's video is just so-so. It's only recorded at 24 frames per second, shake reduction doesn't apply, and it's quite prone to the sensor wobbles. Exposure adjusts in a jarring fashion too frequently. On the other hand, the K-x is one of the cheapest video-capable dSLRs available (at least at the time of this review), and its video is fine in a pinch.
(Shorter bars indicate better performance)
|Time to first shot||Raw shot-to-shot time||Shutter lag (dim light)||Shutter lag (typical)|
(Longer bars indicate better performance)
The Pentax K-x is fast, with good photo quality and an excellent noise profile. Although there are a few things about it that really disappointed us, overall we think most users will like it for what it is -- a flexible, budget dSLR that delivers.
Additional editing by Charles Kloet