Click here to watch Pentax K-x test video in HD

Like Nikon's Motion-JPEG cameras, video quality from the Pentax K-x DSLR is excellent.

In our tests the K-x produced terrific colour accuracy and fine detail, and the chief selling point of HD video on a DSLR - increased control of depth of field thanks to the large sensor - is in evidence here.

And, unlike Nikon's HD-capable DSLRs, which can shoot HD video for a maximum of five minutes, the K-x doesn't have such a tight restriction.

Pop in a 4GB card and you can shoot roughly 11 minutes of 720p footage. An 8GB card can accommodate just less than 24 minutes, which compares excellently to the Nikon D5000's five-minute maximum.

pentax k-x video quality

The Pentax K-x also allows a measure of manual control in video mode. The Canon 500D famously prevents you from setting the aperture yourself in video mode, which reduces your control over the depth of field or brightness in the final video.

The K-x gives you control over the aperture by default - just like in still mode, the aperture blinks on the display if you're going to end up with an under-exposed video.

You can't set the ISO yourself, but having control over the aperture will come into its own if you buy a fast f/2.8 lens. The Nikon D5000 also allows you to set your own aperture in movie mode.

It's not perfect

The K-x is imperfect, though. The so-called 'jello' effect, in which objects which move laterally across the frame appear skewed to one side, was a frequent bugbear during our testing. Fast pans, or vertical objects moving from side to side often wobbled badly.

The Pentax seemed more sensitive to this than other HD-DSLRs we've tested, with even small amounts of camera shake producing pronounced wobble.

It's easy to avoid, as long as you stick to static shots rather than trying to shoot from a moving car, for instance, but it's a restriction we'd rather not have, particularly when our test footage was otherwise so good.

Another unwelcome restriction is the inability to use autofocus while recording video footage. Although this is a hampered feature in other cameras - the 500D uses only contrast detection in video mode - it's something beginners will expect.

Work-arounds

Another way to help avoid the jello effect is to enable the excellent SR (shake reduction) feature.

Pentax's SR works in the same way as Sony's SteadyShot system, by adjusting the sensor inside the camera rather than steadying elements inside the lens.

The chief advantage is you get optical image stabilisation on virtually every lens you can buy. (Pentax points out that screw-mounted lenses - which you need to use with an adaptor anyway - and 645- and 67-system lenses might not work.) So even more expensive fast telephoto lenses will have a few stops of stabilisation.

The system is very effective. At the far end of the bundled 18-55mm kit lens, using SR mode effectively cancelled out camera shake, which is excellent news for those caught in fading light without a tripod, or shooting video.

It also largely cancelled out all but the most severe cases of frame wobble, although it was still something we saw from time to time.

The lens is also one of the best we've seen bundled with a camera. The 18-55, f/3.5-5.6 specifications are nothing special, but it was sharp in our tests. It also feels beautifully smooth and well machined, both on the zoom and focus rings.

This makes it easy to make minor adjustments. And, despite the all-plastic construction it feels better-built than the 18-55mm IS lens that comes with Canon's consumer cameras, and at least as good as the 18-55mm Nikkor lens you get with the Nikon D5000.