Nikon D300S Video
Nikon was the first company to introduce video recording capability in a digital SLR, with last year's D90 digital SLR. Since then, video recording has gone on to become the must-have feature in just about every DSLR announcement, and so it's no surprise to see the Nikon D300S likewise sporting video capability. The D300S' video mode is largely similar to that of the D90, with a couple of important changes. Contrast detection autofocusing is now possible during video recording (albeit with some adverse effects on video and audio quality), and the D300S also now sports an external stereo microphone jack.
Resolution & Recording Time
The Nikon D300S's movie resolutions include 1280x720 (16:9), 640x424 (3:2), and 320x216 (3:2). Video is recorded in Motion JPEG format, in .AVI files. Recording times are limited to five minutes per clip for HD mode, and 20 minutes per clip for the latter two modes. Nikon hasn't explained the reason for the limit as of this writing, but it's likely due to sensor heating issues that might start to degrade image quality. The frame rate is 24 frames per second, and audio from the built-in microphone is monaural, while a standard 3.5mm stereo input jack caters for external microphones. Approximate maximum file sizes of the two larger sizes both seem to be about 600-800MB. The shorter maximum recording time of the higher resolution option seems to about balance the longer recording time of the lower resolution, producing the same size files overall. Nikon says that recording will stop at 2 GB even if it's been less than the 5 or 20 minute time limit in the various modes, but we never made a file larger than 800 MB, regardless of subject choice. (Subjects with lots of fine detail will produce larger images, as the fine detail is harder for the motion JPEG processing used in the D300S to compress.)
The Nikon D300S's movie recording is accessed from Live view mode: You just press the center button in the multi-selector to start or stop recording at any time. Autofocus can be set automatically or manually both before and during movie recording (with some limitations described below), and the zoom can also be set manually at any time. Focus and zoom operation is likely to result in motor / handling noise being recorded on the audio track, although use of an external microphone that is distanced from the camera body should help minimize these issues.
Of course, one of the big advantages of being able to record movies with a Nikon SLR is that you have the full spectrum of Nikon lenses available to you, ranging from ultrawide angle and fisheye lenses all the way to ultra telephotos. You can also obviously use special lenses like the LensBaby Composer for special effects. (While the D300S's video is more oriented toward the making of quick "video snapshots," we can imagine some pros using it just to be able to incorporate special effects like the LensBaby look into their productions.)
The Nikon D300S captures movies at 24 frames/second, the same frame rate used in the motion picture industry. This produces reasonably smooth motion, but we found that rapidly moving subjects close to the camera could look a little jumpy, the same as they do at your local cinema. If you've been using a digicam with a frame rate of only 15 frames/second (fairly common a generation or two back), the D300S's 24 fps will be a welcome upgrade. On the other hand, if you've recently been using a digicam with 30 fps capture, you may find the D300S's video slightly less smooth. Once again, this probably isn't critical for "snapshot" videos, but it's another indication why the D300S really isn't a substitute for a dedicated camcorder.
Prior to recording, you can let the camera set focus during Live View in one of two ways - either the Handheld or Tripod modes. Handheld mode will use the camera's normal (phase detection) autofocus system, which is pretty fast, but briefly interrupts the live-view feed so the reflex mirror can be lowered to let light reach the dedicated AF sensor. Alternately, Tripod mode uses the D300S's contrast-detect focusing, which operates on data streaming from the image sensor, and is rather slow: Expect it to take two or three seconds, longer if it has to move the lens elements a lot.
Once movie recording has started, the Handheld mode autofocusing option isn't available (and half-pressing the shutter button or pressing the AF-ON button while in Handheld mode will stop video recording to perform the AF operation). Autofocus is still available during movie capture when set to Tripod mode, but this uses the slower contrast-detection AF. The autofocus operation will be noticeable in the video track itself, as the camera briefly seeks back and forth to determine the precise point of focus. Sound from the AF motors is also likely to be picked up in the audio track, especially when using the internal microphone.
While better than the previous generation of DSLR video which didn't offer AF during recording at all, the limitations on autofocus during movie recording with the Nikon D300S will probably still give many potential owners pause, as focus is so critical in still photography and dealing with moving subjects would seem to make it even more so. In practice though, we were surprised to find it not nearly the issue we expected it to be. This may be because the lower resolution in video mode greatly increases the effective depth of field: Subjects that would be well out of focus when shot at the D300S's maximum still-image resolution of 12.3 megapixels often looked just fine when viewed at even the maximum video resolution of 1,280 x 720. Lower resolutions only increase this effect. And it's not just the resolution, either, the video compression introduces quite a bit of softness on a frame-by-frame basis, further masking softness due to defocusing.
Of course, manual focusing remains available for those who can't live with the limitations of DSLR video AF, and will allow a new generation to learn what it means to "pull focus" while recording movies, as the point of interest move from one subject to another, or if the subject moves significantly closer to or further from the camera during a segment. "Focus pulling" is a cinematic technique often performed by someone other than the camera operator, who is usually too busy framing the image to attend to focus as well. But millions of Nikon D300S owners will be able to try a technique that few camcorder owners can.
In our own admittedly limited playing with video recording on Nikon's DSLRs, we've found that pulling focus during a recording is a skill that requires some learning, particularly if there are things going on in the scene that need paying attention to. If we knew the approximate locations where the subject would be at the start and end of a clip (think of a video of a Little Leaguer sliding into home), we could check the corresponding positions of the focus ring and then try to repeat them while the action was taking place. This was a little hard to do with only a ring to grab onto, as the tactile reference for the different focus positions was pretty weak; a lever would have made the starting and stopping positions much more evident and easier to remember. As we expected when we reviewed the Nikon D90's video mode, aftermarket gadgets have begun to appear that aim to solve some of the issues with handling and focusing DSLRs during video recording.
If you don't know in advance how the subject is going to move, you can try to judge focus from the image on the D300S's rear-panel LCD and adjust accordingly. The exceptional resolution and sharpness of the LCD makes this more practical than it might sound. Once again, some practice (and inherently good reflexes) are required, but given enough practice, it could work reasonably well.
The Nikon D300S has an internal microphone concealed behind three small holes on the front of the camera body. The D300S also provides for an external mic, courtesy of a 3.5mm stereo input jack under a flap on the left side of the camera's body - a very useful upgrade from the D90's fixed internal, monaural microphone. Another upgrade from the D90 is adjustable sensitivity for the microphone. There are three sensitivity levels to choose from (Low, Medium and High), along with Auto gain, and Off settings. The settings apply to the built-in microphone as well as to an external mic. We found the D300S's internal microphone to be quite sensitive when using Auto gain. It has no problem picking up even quiet conversation from across a room, as long as there are no background noises. Ah, but there's the rub: The mic will pick up all sorts of background noise if you're not careful. Given that most users will likely be using the D300S's video recording for short clips of memorable moments, its tendency to pick up every sound is probably a positive feature. For those wanting the best audio quality, an external microphone will almost certainly prove a better choice however, allowing selection of a microphone with the desired characteristics, as well as reducing the effects of noise from handling the camera body or using the focus and zoom mechanisms. The selectable microphone sensitivity is also a welcome improvement.
Audio is recorded with a bit depth of 16-bits and a sampling rate of only 11.025 kHz. That's a pretty low sampling rate. The Nikon D3S records audio at 44.1 kHz while the Canon 7D and many camcorders record at 48 kHz, so the D300S's recorded audio isn't high quality.
Rolling Shutter Artifact ("Jello Effect")
There was one aspect of the Nikon D300S's video that we found less than wonderful, though, namely the way its progressive data readout from the sensor chip can produce distortions in the image when the camera or subject moves suddenly. The D300S records its movies at 24 frames/second, but like all digital SLRs, the way it clocks data off its sensor chip means that it takes some time to read out each frame - on the order of 1/24 second for the D300S. By contrast, most camcorders grab each frame at a single moment in time, with all of the pixels in the image acquired simultaneously.
The consequence of this progressive capture is that any movement of the camera or subject between the beginning of a given frame's capture and the end of it will produce distortions in the shape of the image.
We first noticed this effect while reviewing the D90, when panning rapidly to follow fast motion: Trees and buildings would appear to lean opposite the direction of our panning. On the other hand, if you're panning slowly to take in a larger scene, you're not likely to notice the effect at all. More disconcerting, once we became sensitized to the phenomena, we noticed our video subjects "jiggling" slightly in response to even fairly minor camera shake as we were hand-holding the D90, and the D300S suffers the very same issues. Lens-based IS helps with this somewhat, but we'd be much happier if Nikon could figure out a way to grab the image data all at once and then read it off to the memory card before starting the next frame grab.
You can control the aperture used for movies by selecting Aperture Priority or Manual exposure mode prior to entering Live View mode. The smallest aperture supported for movies is f/16, regardless of the lens attached. Shutter speed and ISO sensitivity are always under the control of the camera. It appears that the D300S's autoexposure during movie recording is performed by varying sensitivity and/or shutter speed in steps (1/3 EV?) rather than being continuously variable, which can lead to some abrupt, stepped changes in exposure. Only matrix metering is supported during movie capture, however exposure compensation can be adjusted up to +/- 3 EV while recording, and exposure can be locked using the AE-L/AF-L button. You can apply Nikon's Picture Controls as well as specify the color space for movies, as long as they are selected before recording begins. This is useful if you'd like to for instance record in monochrome, or with more saturated colors, etc.
Video Examples: Dave shot some examples of video with the D300S, so you can see what the different resolution levels look like. Click on any of the thumbnails below to bring up each video in a new window.
Nikon D300S Video Examples
Three Video Sizes
Options include 1,280 x 720, 640x424, and 320 x 216 pixels, all at 24 frames/second
(Click on any thumbnail to launch/download the movie in a new window)
1,280 x 720 pixel video
(but JPEG compression hides detail you'd see in that size still image)
640 x 424 pixel video
320 x 216 pixel video
As noted earlier, the Nikon D300S's video imagery is not only considerably lower resolution than its still images, but the heavy JPEG compression applied to the video frames further reduces detail. The upside of this is that the effective depth of field is quite a bit greater than you'd find in its still images at similar focal length and aperture. Note in some of the shots how little the apparent focus changes as wonder-dog Charlotte runs toward or away from the camera.
In the highest-res shot above, the lens was initially focused somewhere between Marti and the camera, so she's a little soft at the start of the clip. That said, I found it quite surprising how little apparent sharpness changed as Charlotte approached and receded from the camera.
Depth of field
One of the key benefits to shooting video with a digital SLR is the narrow depth of field available to an SLR's lenses. Below you can see two videos, one shot wide open, and the other stopped down.
It's easier to isolate your subject from the background when shooting with a wider aperture.
Here the background is distracting thanks to the greater depth of field, but of course there are times when you want that too, as in landscape photography.