Pentax K-x

Motion (7.00)

The Pentax K-x can only record video with a 24p frame rate, although it has both HD (1280 × 720) and SD (640 × 480) recording options. The videos shown below have been heavily compressed during the upload process to YouTube, but they should still give you an idea about how well each camera captures motion video. More on how CamcorderInfo tests motion.

The Pentax K-x showed very little artifacting in our motion test, but its video wasn’t that smooth. The camera appeared to render somewhat jerky motion, especially when compared to the kind of motion produced by a traditional camcorder. Still, the fact that the K-x had such low amounts of artifacting is definitely a plus.

The Nikon D5000 wasn’t very good in our motion test. Its 24p footage had a lot of artifacting and frequency interference. We noticed jagged lines (like lightning bolts) on our black and white pinwheel, as well as some blur on our RGB pinwheel. The camera simply couldn’t render motion that looked good in our testing.

The GF1 has a couple of different recording options for HD video—a 60p mode and a 30p mode. We had a good deal of trouble dealing with the GF1’s 60p setting when we imported the footage onto our computer (the videos played back at double speed), but we chalked this up to a compatibility issue with Panasonic’s AVCHD Lite compression system. Shooting with the GF1’s 30p mode, which uses MJPEG compression, we saw some artifacting, pixelation, and choppy video, but we were able to import the files to our computer with no problems.

The Canon T1i did produce fairly artifact-free video in our motion test, but the camera was marred by its unusual 20p frame rate when shooting 1920 × 1080 video. The footage looked awkward and choppy due to the low frame rate, and for this reason we recommend the Canon 7D instead. The 7D offers similar video performance to the T1i, but includes more popular 24p and 30p frame rates instead. The Canon T1i does, however, include a 720/30p setting that showed some better results in our motion test.

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Video Sharpness (9.77)

The Pentax K-x appeared to deliver a sharper image than most video-DSLRs that record 720p video. According to our measurements, the camcorder managed a horizontal sharpness of 650 lw/ph and a vertical sharpness of 600 lw/ph. These numbers are slightly better than the Nikon D5000 and Panasonic GF1 put up, but most of the DSLRs with 1080p capability had better sharpness numbers (because they shoot video at a higher resolution).

The problem with the K-x when it comes to video sharpness is the fact that the camera has no HDMI output. You can only output video on the camera using the proprietary AV-out port (that also doubles as a USB port) on the left side of the camera. This means you’re viewing the 1280 × 720 HD video through a low-quality analog connection when you connect the K-x to a television—so you’re really losing all that HD quality and sharpness when you watch videos this way. You can import the footage to your computer and watch it in HD there, however, but we’re guessing you’d rather watch HD video on a large HDTV if given the option. More on how CamcorderInfo tests video sharpness.

Low Light Sensitivity (0.97)

Testing the Pentax K-x with its kit lens, the camera didn’t do a very good job with low light sensitivity. Still, compared to some of the abysmal results we’ve gotten from other video-capable DSLRs, the K-x’s numbers don’t look too bad. The K-x required 23 lux of light to register 50 IRE on our waveform monitor. Of the DSLRs we compared it to below, only the Nikon D5000 had a better low light sensitivity (the Panasonic GF1 and Canon T1i were just slightly worse than the K-x).

Of course, much of a camera’s low light sensitivity score comes down to what kind of lens you are using. The kit lens on the K-x is an f/3.5 18-55mm lens, so it isn’t that fast. If you shoot video with a lens that has faster aperture settings, you’re likely to get better low light sensitivity in video mode on the K-x.