Pentax K-7 Review

Video

Nikon and Canon started the trend with the D90 and 5D Mark II respectively and it was only a matter of time before other manufacturers would follow. Now, with the K-7, Pentax has introduced its first DSLR with a video recording capability.

Like previous video-enabled DSLRs the K-7 does not offer the fast AF or the same degree of control over video capture as a dedicated camcorder would, but the ability to shoot movies with a large sensor (with the shallow depth of field that this brings) and interchangeable lenses no doubt brings a whole range of new creative possibilities to budding videographers.

Video specification

The K-7's highest available video resolution of 1536 x 1024 pixels is slightly uncommon in so far that it is located somewhere in between the 1080p and 720p standards that have been adopted by other manufacturers. It also means an unusual 3:2 aspect ratio rather than the more usual 16:9. Additional resolution settings are 1280 x 720 (720p) and 640 x 480 (VGA). At all resolution settings video footage is recorded at 30 frames per second. Movie files are saved in the high quality, but very large, Motion JPEG format.

Using Movie Mode

Shooting a video on the K-7 is a very 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 the 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-7 will adjust the aperture if the brightness of the recorded scene changes (the click sound is often clearly audible in the recording). 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-7 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 but if sound is important in your video there is also a connector for an external mic. The optical image stabilization is activated by default but can be switched off.

Movie mode displays

Movie menu showing the three available video resolutions. Shake reduction can be turned on or off.	Aperture control can be set to either Auto of 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

Like most of the video-enabled DSLRs that we've seen so far the K-7 produces very good high HD quality footage with fairly smooth motion even at the highest resolution (although you'll need a fairly powerful computer to play the files smoothly). The K-7'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 the use of Auto ISO can, as you would expect, leads to grainy video output in low light. However, the K-7 is not noticeably worse in this respect than any of its competitors.

Like pretty much all other video-DSLRs the K-7 can suffer 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-7 is pretty average in this respect. The effect is noticeable but you have to pan pretty quickly to make it too much of a nuisance. An example panning video is included.

Another interesting effect appears when you change the framing quickly from a dark scene to a brighter one. The camera first adjusts the gain to adapt to the new lighting conditions and then changes the aperture. When that happens the gain is then not decreased sufficiently quickly which results in a flash-like split-second of extreme over-exposure. When the aperture changes there's also an audible click sound recorded. We've seen this effect on other DSLRs before but to a lesser extent. This problem can be avoided by fixing the aperture before starting to record.

All in all we can say that compared to the movie mode on any digital stills camera or consumer camcorder we've used the K-7's video quality is quite impressive. Usability of the video mode is a completely different matter and the area in which a dedicated camcorder is miles ahead. In any case, below you'll find some examples of videos taken with the K-7 for you to download and draw your own conclusions.

Sample video 1

This video was shot in 1536 x 1024/30fps mode. It records a screen-filling 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.

1536 x 1024, 30 fps. AVI (MJPG) file. 9 sec. 44.6 MB

Sample video 2

This video was also shot at 1536 x 1024/30fps and shows a problem that we encountered quite frequently on the K-7 - a bright flash and click as the camera adjusts its sensitivity and aperture slightly out-of-sync. You can also spot some evidence of moire on the wall of the building to the right.

1536 x 1024, 30 fps. AVI (MJPG) file 11 sec. 52.8 MB

Sample video 3

This 720p/30-fps video was shot in the evening and shows the K-7's performance in low light.

1280 x 720, 30 fps. AVI (MJPG) file. 15 sec. 81.6 MB

Sample video 4

This video with panning, shows the extent of the rolling shutter which can be a problem on CMOS sensor cameras recording video.

1536 x 1024, 30 fps. AVI (MJPG) file 6 sec. 29.9 MB

Sample video 5

This video gives you an idea of the capabilities of the internal microphone. While it is not doing a bad job an external mic is certainly a sensible investment if sound quality is important in your videos.

1536 x 1024, 30 fps. AVI (MJPG) file 14 sec. 73.4 MB