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Pentax K-x Digital Camera Review$650.00
The Pentax K-x records video using the Motion JPEG (MJPEG) compression. This is the same system used by the Nikon D5000, as well as a number of point-and-shoot digital cameras that offer video modes. MJPEG is a common compression system, so compatibility with your media player or editing software shouldn't be an issue. Motion JPEG isn't very efficient, however, and it isn't regarded as the highest-quality compression system for HD video. The MJPEG video files recorded on the Pentax K-x are saved as AVI files.
There aren't too many format options for recording video on the K-x. There's a single HD recording setting, which captures 1280 x 720 video with a 24p frame rate, and there's a standard definition option that records with a 640 x 480 resolution (also at 24p). The camera offers three unnamed quality settings for video recording, each of which is represented by a series of stars in the menu. We assume these quality settings each use different bitrates because you can record more video with the one-star setting than you can with the three-star setting — but Pentax doesn't list any specs or bitrates when referring to the quality options. Pentax simply calls the quality settings Best (three starts), Better (two stars), and Good (one star). Find out how the performed in our video image quality test./r:link_to_content
Since the K-x has no continual autofocus feature we can't really give its auto controls a full recommendation. If you want to focus while recording video you must do so manually (by rotating the lens ring), and if you want to use autofocus you have to press the shutter button halfway before recording (just like you do to take a still photo).
The camera's other auto controls aren't bad. Auto white balance generally worked well in video mode, but it wasn't perfect in all kinds of light. The camera offers plenty of white balance presets, however, so you shouldn't have any trouble fine-tuning the color temperature to your preference. Auto exposure adjustments were very slow, but the system worked smoothly when we moved from light to dark scenes. Some users may like the slow transition of exposure (it almost looks like you are rotating a dial manually), while those used to the snap-like exposure offered on many consumer camcorders will probably be disappointed.
Zoom is controlled on the K-x by rotating the large lens ring on the attached lens. The quality and feel of this ring will be different depending on what lens you have connected to the camera—as will the zoom ratio. The kit lens with the Pentax K-x is an 18 - 55mm lens, which is close to a 3x zoom. You can zoom while recording video with the K-x, but you must do so by rotating the lens ring.
The K-x has no continual autofocus feature, which means the only way to keep a moving subject in focus while you record is to do so manually by rotating the focus ring. This is an issue that plagues many video-capable DSLRs, with the notable exception of the Micro Four Thirds models from Panasonic and Olympus.
In addition to not offering a live autofocus feature, the K-x also has one of the loudest and slowest autofocus mechanisms of any video-capable DSLR we've tested. The camera's live view mode must go blank for a moment while the camera performs an autofocus (which is done by pressing the shutter halfway or by pressing the AF button), and you cannot perform any kind of autofocus while recording is taking place.
The K-x isn't loaded with manual controls in video mode, but adjustments to exposure and aperture can be made (shutter speed can't be controlled manually). There are 13 increments of basic exposure control on the K-x, ranging from -2 to +2 in 1/3 EV steps. Adjusting exposure is quite simple, but it cannot be performed while recording is taking place. When you set a manual exposure prior to recording, however, this exposure is locked for the duration of the clip (auto exposure is turned off).
To set aperture manually in video mode you must go into the camera's menu and switch aperture from auto to fixed. The camera offers plenty of aperture values, ranging from f/3.5 to f/40, but you have to start recording before you can see what kind of exposure level your manual aperture is going to give you. To compensate for this, the aperture selection will blink in red if there isn't enough light to use it. You can still use these aperture settings, but your recorded image will likely be too dark.
As with shutter speed, ISO cannot be set manually on the K-x. You can set white balance manually, but you must leave video mode to do so. You can then put the camera back into video mode (with a manual white balance selected) and use your manual white balance. We're kind of annoyed by this roundabout system, but quirks like this are rather common on video-capable DSLRs.
There is also an image stabilization feature that can be turned on and off in video mode, but it makes loud, consistent noises while engaged. We recommend turning the stabilization feature off if you are at all concerned about picking up unwanted noises on the K-x's built-in microphone (the crackling sound created by the stabilization system can also be very annoying to listen to for extended periods of time). Still, the built-in mic on the K-x is not very good to begin with, so if you care about audio you shouldn't be using it to record sound in the first place.
The audio features on the Pentax K-x are the epitome of 'bare-bones.' All the camera has is a tiny monaural microphone on its upper left side. The mic isn't well placed, as it's positioned right in the spot where you might end up resting your fingers if you don't like holding the lens while you shoot. The Pentax K-x picks up tons of operating noise with its built-in mic, but this is something we've seen from most video-capable DSLRs. When using the built-in mic, expect to hear plenty of noise from the autofocus motor, lens and dial movement, and image stabilization system (if it is turned on).
The group of video-DSLRs listed in the table below are all sub par models when it comes to audio features. None of them have external microphone inputs, and each of them lack any special audio controls — except for the GF1, which has a mildly useful wind cut option. The point is, if you need quality audio with any of these cameras you're going to have to record to a separate audio device entirely.