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Video

It appears none of the established manufacturers can afford to launch a DSLR without video capability these days and consequently the K-x is, after the K-7, the second Pentax DSLR to come with a HD video mode.

Pretty much like all currently available video-enabled DSLRs the K-x does not offer the fast AF or the same degree of control over video capture as a dedicated camcorder. However, the ability to shoot movies with a large sensor and therefore a cinema-like, shallow depth of field, and interchangeable lenses will be an attractive option for most photographers with an interest in videography.

Video specification

Unlike the K-7 which features a rather unusual 1536 x 1024 pixels (3:2) aspect ratio the K-x comes with a more standard 1280 x 720 pixels (720p) at 24 fps video mode. There is also a 640 x 416 pixels mode. Movie files are saved in the high quality, but very large, Motion JPEG format. Resolution and frame rate aside the K-x's movie features are pretty basic. There is no connector for an external stereo microphone, no wind-cut function and no manual controls (you can fix the aperture before recording though).

Sizes 1280 x 720 (720p) at 24 fps
640 x 416 (VGA) at 24 fps
Audio Mono (Internal Mic)
Format MJPEG (.AVI)
File size 5.8 MB/sec (720p), 1.7 MB/sec (VGA)
Max file size per clip 4.0 GB
Running time 25 min or until SD card is full

Using Movie Mode

Shooting a video on the K-x is very similar to the K-7 and a straightforward affair. Turn the mode dial to movie mode and press the shutter button to start recording; press again to stop. Once the camera is recording it is doing everything fully automatically and does not react to a press of any button other than the shutter button. AF is not available while recording video, therefore manual focus or pre-focusing by pressing the AF-button before you start recording are the only options. This is not a major disadvantage given that the video-mode AF on all current video-enabled DSLRs is so painfully slow that it is virtually unusable (the mirrorless Panasonic GF1 shows how it should be done). It also means that there are no AF-motor sounds to be recorded by the internal microphone as happens on other cameras.

Aperture, shutter speed and sensitivity are all set automatically. You can however choose to fix the aperture before you start the video capture which gives you a degree of control over depth of field in your videos. In Auto Aperture mode the K-x will adjust the aperture if the brightness of the recorded scene changes. In Fixed Aperture mode the camera achieves the same goal by only adapting the sensor sensitivity.

Unlike some other recent video-enabled DSLRs the K-x does not allow you to take any still images during video recording, you'll have to turn the mode dial to one of the still modes in order to take a picture. You can't change the amount of on-screen information during video capture either. The camera's internal microphone records monaural sound. There is no connector for an external microphone. The optical image stabilization is activated by default but can be switched off.

Movie mode displays

Movie menu showing the two available video resolutions. Shake reduction can be turned on or off. Aperture control can be set to either Auto or Fixed.
 
Once recording has started the record icon and remaining time are displayed at the bottom of the frame. During recording the camera does not react to any button presses apart from the shutter button which will stop recording.  

Video quality comments

The K-x's video footage is not quite as detailed as the 1080p output of some of the higher-priced competitors but certainly in-line with other 720p video-DSLRs. It produces good quality HD footage with fairly smooth motion (although you'll need a fairly powerful computer to play the files smoothly). The K-x's sensor is APS-C size and therefore you can't quite create the same depth of field effects as on a full-frame-camera such as the Canon EOS 5D Mark II but you still get a much shallower, more cinematic depth of field than with any digital compact camera. When recording video more or less all functions are automated (you can fix the aperture though) and inevitably the use of higher sensitivities in low light leads to grainy footage. However, the K-x is not noticeably worse in this respect than the competition and, due to the comparatively small size of the video output, the image noise is less intrusive. However, you should be aware that the K-x appears not to be using its full sensitivity range of up to ISO 12800 when recording video. This can result in underexposed video output in very low light.

Like pretty much all other video-DSLRs the K-x suffers from distortion caused by its rolling shutter. The readout of the sensor means horizontal lines of the image are scanned, one after another, rather than the whole scene being grabbed in one go. The upshot is that verticals can be skewed if the camera (or the subject) moves too fast - the top of the image has been recorded earlier than the bottom, so vertical lines can be rendered as diagonals. The K-x is pretty average in this respect. The effect is clearly noticeable but you have to pan fairly quickly to make it too intrusive.

When changing the framing from dark to bright scenes or vice versa the exposure adaption via change of aperture and/or gain is comparatively smooth. Below you'll find some examples of videos taken with the K-x for you to download and draw your own conclusions.

Sample video 1

This video was shot in 1280 x 720/24fps mode. It records a large, high quality image with smooth motion. Make sure your video card is powerful enough for watching these large video files. On slower machines the motion can appear jerky.

1280 x 720, 24 fps. AVI (MJPG) file. 15 sec. 78.1 MB

Sample video 2

This video was also shot at 1280 x 720/24fps and shows the video quality in low (natural) light.

1280 x 720, 24 fps. AVI (MJPG) file. 6 sec. 30.5 MB

Sample video 3

This 720p/24-fps video was shot in the evening with a long lens and shows the K-x's performance under low, artificial light.

1280 x 720, 24 fps. AVI (MJPG) file. 6 sec. 30.9 MB

Sample video 4

This video was shot at 1280 x 720/24fps in bright sunlight.

1280 x 720, 24 fps. AVI (MJPG) file. 7 sec. 38.1 MB

Sample video 5

This video shows how the camera deals with a transition from dark to bright scenes and vice versa using gain and aperture.

1280 x 720, 24 fps. AVI (MJPG) file. 7 sec. 34.9 MB

Sample video 6

This video was taken in very low light. It appears the K-x is not using its full ISO range in video mode which results in underexposed video output in very low light. The camera does not feature a wind-cut function. Therefore, as you can hear, the quality of sound captured by the internal microphone in windy conditions can be fairly dismal.

1280 x 720, 24 fps. AVI (MJPG) file. 6 sec. 29.4 MB

Sample video 7

1280 x 720, 24 fps. AVI (MJPG) file. 6 sec. 31.5 MB
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