The D300S is still in fairly exclusive company, being one of the first large-sensor cameras to offer movie recording capabilities. In common with the D90 and D5000, the D300S offers 720p at 24 frames per second.

Sizes • 1280 x 720 (24 fps)
640 x 424 (24 fps)
320 x 216 (24 fps)
Audio 16-bit, 11 kHz (Mono using internal mic, Stereo with external unit)
Format AVI (Motion JPEG)
File size ~2.3 MB/sec (HD)
Running time 5 min in HD, 20 min all other modes

The results are impressive when compared to the output from compact cameras - though wouldn't stand up to the kinds of scrutiny we apply to still images. However, because the sensor (and its readout method), probably wasn't designed specifically with movies in mind, there are some interesting effects that can be induced. The readout of the sensor means movies are created with a rolling shutter (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 moving vertical lines can be rendered as a diagonals. (Click here to download a demonstration using a Nikon D90)

However, although movie mode still feels a little tacked-on, it is significantly improved over existing Nikon DSLRs. The biggest difference it that the camera can now use its contrast-detection autofocus system while shooting movies (by setting Liveview mode to 'Tripod'). We'd recommend using an external microphone if you're likely to use this features, since the noise of the camera or lens autofocusing can be heard on the movies. It's also worth noting that, even when using lenses with Nikon's ultrasonic AF-S motors, focusing isn't particularly snappy, so will have to be worked into videos as an 'effect,' rather than an annoyance.

Aperture (and hence depth-of-field) must be selected before entering Live view mode, so the video adjusts its exposure using variable gain, rather than by adjusting shutter speed or aperture. This automatic exposure can result in rather 'stepped' exposure changes - the aperture is locked so the problem seems to stem from amplifier stepping (clearly visible as the bus passes in the first video).

The resultant movies are certainly good enough for many uses (though broadcast might be pushing it - the D300S isn't primarily a video capture device), capturing a lot of detail and playing smoothly. The large sensor means the performance in low light is very good, though we do see some slight banding in very dark situations.

The sound recording has a fairly low sampling rate (11 kHz, compared to the 48 kHz sound recorded by most dedicated video cameras), collected either through an external mic or the internal unit that tends mainly to record the sound of the camera operator.

Movie mode displays

Under the Movie Settings option on the Record menu, you can choose video size (up to 720p/24) ...the microphone sensitivity and whether movies are stored to CF or SD card.
Holding 'Play' and pushing left or right on the four-way controller toggles between brightness and recording volume, Play and up or down adjusts the selected setting. Pressing the central button on the four-way controller engages record mode. Once recording, Play and up or down on the four-way controller adjusts brightness.
During playback the four-way controller provides fast-forward/rewind, pause and stop controls. The built-in speaker means you can listen to the soundtrack (if recorded).  

Video editing

The D300S allows you to edit the videos you've shot. The editing is pretty primitive, allowing only the start and end points to be trimmed but it's unlikely many people would want to do anything more complicated on the camera, given the sophistication of editing software available.

Pressing the 'OK' button when in movie playback mode allows you to trim your movie files. The left and right keys progress through the video, then pressing up selects the cut point.

Sample video (with moderate motion)

1280 x 720, 24 fps. AVI (motion JPEG) file. 7 sec. 19.1 MB
1280 x 720, 24 fps. AVI (motion JPEG) file. 6 sec. 13.2 MB
1280 x 720, 24 fps. AVI (motion JPEG) file. 9.3 sec. 25.9 MB (Trimmed in camera)

Sample video (showing shallow depth-of-field)

1280 x 720, 24 fps. AVI (motion JPEG) file. 5.9 sec. 7.0 MB (Trimmed in camera)