For the most part, the K-x is very fast. It takes 0.7 second to power and shoot, which is a bit slow but not bad. Time to focus and shoot in good light is a zippy 0.3 second, increasing to only 0.5 second in low light. Two sequential JPEGs run 0.4 second, with a slight bump to 0.6 for raw; its 1.2-second shot-to-shot time with flash is the only cloud in the K-x's speed sky, although Sony generally does worse. And typical continuous-shooting is a solid 4.2fps.
Other measures of performance aren't quite so rosy, most notably its image stabilization. For whatever reason--excessive mirror slap vibration, a stiff shutter, or simply a poor implementation--I had a lot more photos with camera shake, even at high shutter speeds and modest focal lengths, than I'm used to seeing these days. Furthermore, the LCD is fairly coarse, which makes it hard to accurately judge if the photos are sharp enough. It's also difficult to see in direct sunlight. And, as is typical for all but the Sony dSLRs, Live View autofocus is pretty slow.
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 a bit of degradation of detail in shadow areas at ISO 800, but even at as high as ISO 1,600 I found the images quite acceptable. By ISO 3,200, the decrease in detail becomes obvious. Pentax rightfully considers ISO 12,800 (and ISO 100) an expanded mode, though I'd probably add ISO 6,400 to that as well. Though there's still usable detail at ISO 3,200, by ISO 6,400 noise and noise reduction artifacts are obvious, even when scaled down. I wouldn't recommend using ISO 12,800 as a rule, but this is actually pretty good, and not just for a sub-$800 model. You lose a lot of the shadow detail and there's obvious blotchiness, but the overall photo retains good saturation and it's more than acceptable for small Web use. However, the K-x maintains good color consistency across all the ISO sensitivity levels.
Pentax's 18-55mm kit lens doesn't display a lot of distortion at its widest, 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. It's worth noting that this is a generally nice kit lens, with an exceptionally close focus for its cohort.
Though the K-x's default Bright image setting produces a slight color shift over neutral, despite ostensibly bumping up only contrast and sharpness, it's not nearly as severe a shift as in Sony's comparable models and unlike Sony Pentax provides a Natural option. However, Pentax's automatic white balance normally tends to be on the cool side, which results in an overall color cast.
The video, however, is just so-so. It's only 24fps, shake reduction doesn't apply, and it's quite prone to the sensor wobblies. Exposure adjusts jarringly too frequently. On the other hand, it's the cheapest video-capable dSLR (at least at the time of this review), and it's fine in a pinch.
As long as you're willing to put up with some of its quirks, the Pentax K-x will probably deliver on your dSLR expectations.
(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)