Nikon D5100 Video

Nikon D5100 Video Recording

Nikon pioneered video capability in its D90 digital SLR, and it's rapidly become a must-have feature, with essentially all the major manufacturers now providing some form of video capture in their DSLRs. Positioned as an affordable mid-range model, the Nikon D5100 includes a fairly sophisticated feature-set that offers significantly more creative control than in many DSLRs, while retaining some options that cater more to consumer needs.

Like the D3100 before it, the D5100 can offer live contrast detection autofocusing with tracking capability during video recording, albeit with some adverse effects on video and audio quality. Experienced videographers will find intriguing possibilities in the D5100's ability to control the lens aperture manually before capture starts, to accept an external microphone, and to adjust audio gain. The D5100 also offers Full HD (aka 1080p) high definition video capture, ensuring that its movies -- all recorded using H.264/MPEG-4 AVC compression -- will look their best even on the latest high-def displays.

Nikon D5100 Basic Video Specs

• 1080p (1,920 x 1,080) or 720p (1,280 x 720) HD recording at 30 / 25 / 24 fps
• 640 x 424 SD recording at 30 / 25 fps
• MPEG-4 / H.264 AVC compression, .MOV container
• Full-time live autofocus is possible during recording, including tracking and face detection, albeit with actuation noise levels depending on the lens used
• Single-servo auto and manual focus also possible
• AF point position and size can be manually controlled
• Programmed-auto or aperture-priority exposure (set before recording starts; no shutter-priority)
• Exposure compensation and lock are available both before and during recording
• Picture control system provides creative options
• Monaural audio recording via built-in microphone
• Stereo audio recording via external microphone jack
• Image stabilization during video capture, if offered by lens
  

Nikon D5100 Video: Image Size, Frame Rate, and Encoding

The Nikon D5100 records movies at three progressive scan resolutions: either 1,920 x 1,080, 1,280 x 720, or 640 x 424 pixels. The highest resolution 1,920 x 1,080 pixel mode is commonly known as Full HD or 1,080p, and has a 16:9 aspect ratio. The intermediate 1,280 x 720 pixel resolution also has a 16:9 aspect ratio, and is better known as 720p. These both offers a choice of three frame rates, nominally listed as 30, 25, and 24 frames per second, although the highest and lowest rates are actually 29.97 and 23.976 fps. When the D5100's video output is set to the North American NTSC format, a choice of the nominal 30fps and 24fps movie recording rates are available. If switched to PAL format, the D5100 offers a choice of 25 fps or nominal 24 fps rates. Finally, the non-standard 640 x 424 pixel mode has an approximate 3:2 aspect ratio. With this standard definition mode, recording frame rates are fixed at either the nominal 30 fps for NTSC, or 25fps for PAL.

Regardless of resolution and frame rate, recording times are limited to 20 minutes or four gigabytes per clip, whichever limit is reached first. Nikon hasn't explained the reason for the time limit as of this writing, but it's likely due to sensor heating issues that might start to degrade image quality. The Nikon D5100 records movies using H.264/MPEG-4 AVC compression with Linear PCM audio, and stores them in .MOV files. Compared to the Motion JPEG format used by some cameras, H.264 is much more conservative of memory card space. It also avoids some of the severe image quality loss suffered by AVCHD cameras, when faced with significant amounts of change in image content between frames. (AVCHD uses a subset of the H.264 standard, which among other things mandates a limit in recording bandwidth, translating into a lesser ability to convey rapidly-changing detail.) The choice of H.264 comes with the requirement of greater processing power, though -- not only from the camera when recording, but also when playing back or editing videos. The more sophisticated encoding used in the H.264 standard requires quite a bit of processor power to pull it apart and put it back together again, so frame-accurate editing of H.264 requires a fast processor and capable editing program.

Here's a list showing what to expect for file sizes with the Nikon D5100's video recording:

Nikon recommends using an SD card with at least a Class 6 rating to capture and playback movies.

Nikon D5100 Sample Videos

Here are some examples of video from the Nikon D5100, showing typical results under daylight and night conditions.

Nikon D5100 Video-Mode Focusing

Unlike some of Nikon's digital SLRs, the D5100's Live View mode -- from which Movie recording is initiated -- lacks the company's separate Handheld and Tripod modes. Instead, autofocus during live view and movie capture is always performed using contrast detection autofocus, which operates based on data streaming from the image sensor -- the same technique referred to as Tripod mode on some models. (On cameras that offer a choice, you can switch to Handheld mode to use the camera's phase detection autofocus system before movie starts, so long you don't mind a brief interruption of the live-view feed so that the reflex mirror can be lowered to let light reach the dedicated AF sensor. All of Nikon's DSLRs, like the vast majority of interchangeable-lens cameras, must rely on contrast detection AF during video capture.) The good news is that, while not quite in single-lens direct view or compact camera territory, the D5100's contrast detection autofocus is quicker than the average, among those offered by its peers. A measure of Nikon's confidence in the D5100's contrast detection performance can, perhaps, be read from the fact that it not only offers full-time AF during movie capture, but also provides an AF tracking function.

As in the earlier consumer-oriented D3100 model, the Nikon D5100's contrast detection-based continuous autofocus mode carries a different name from its phase-detection equivalent. Dubbed Full-time Servo AF (AF-F for short, as opposed to AF-C / Continuous-Servo AF for phase detect), this function does involve some hunting around the point of focus, and can lag behind changes in your subject's focus distance somewhat. If your subject is relatively static, you can instead opt for the Single-servo AF mode, which will still allow you to perform single autofocus operations during video capture by half-pressing the shutter button. You can, of course, also focus manually by appropriately setting the Focus-mode selector on the camera's front panel (as well as that on the lens, if applicable).

The D5100 offers four AF-area modes for use during movie capture: Face-priority AF, Wide-area AF, Normal-area AF, and the aforementioned Subject-Tracking AF. The Wide and Normal-area modes are self-explanatory, providing two different focus area sizes, which can be manually positioned anywhere within the frame (and even moved during video capture.) Face-priority AF -- which can identify up to 35 individual faces within the frame during live view, but an (undisclosed) lesser number during movie capture -- will select the closest subject among the group when adjusting focus. This individual will be indicated by a double-yellow frame on the D5100's LCD panel. Finally, the Subject-tracking AF function allows you to manually position the point from which autofocus tracking should commence, and to start or stop the function by pressing the OK button when your subject falls under the AF point. The D5100 will then indicate the point at which it is currently tracking the subject with a focus frame that changes between either green to indicate a focus lock, or red to indicate that a focus lock hasn't currently been attained.

Like most interchangeable lens cameras capable of AF during video, the D5100 has a tendency to pick up autofocus drive noise quite clearly in the audio track of its movie clips. This can at least be mitigated somewhat by use of an external microphone, and by adjusting the D5100's three-step manual gain control, however. If AF noise is too much of an issue, you can of course switch to focusing manually, during a recording, and the true manual operation of AF on Nikon's lenses means you can do this more or less silently, simply by being careful about turning the focus ring. (Some interchangeable lens cameras we've tested use "fly-by-wire" focusing, whereby the focus ring only instructs the camera to move the lens elements rather than moving them directly via a mechanical coupling. This can mean that focus operation is still audible, regardless of how slowly you turn the focus ring. With true manual operation of its lenses, the Nikon D5100 doesn't have this problem, although it's possible that third-party or older Nikon lenses might produce audible noise while their focus was adjusted.)

As we've noted in other SLR reviews, the good news with focusing for video is that you can get surprisingly good depth of field in video mode by stopping the lens down, thanks to the relatively low resolution of the video image. With a pixel resolution of only 2.1 megapixels in the Nikon D5100's highest-resolution 1,080p "Full HD" mode, 0.9 megapixels in 720p HD mode, and just 0.3 megapixels in the standard-definition mode, images that would be unacceptably blurred as 16 megapixel still shots look perfectly fine as video frames. This not only provides greater depth of field at any given aperture, but is also more forgiving of diffraction limiting at very small lens apertures. Diffraction at small apertures means you'd usually want to avoid f/16 or f/22 for still images, but again, the results generally look perfectly fine at video resolutions. Bottom line, with the Nikon D5100's lens set to f/16 or f/22 (assuming you're shooting under fairly bright conditions), you'll be surprised by how little focus adjustment is needed during a typical video recording.

Nikon D5100 Video Exposure Control

With the Mode dial set to any position except A or M, the main exposure variables -- shutter speed, aperture, and ISO sensitivity -- all remain under automatic control when recording movies with the Nikon D5100. If the Mode dial is in the A or M positions, however, you can shoot movies in Aperture-priority mode, with the proviso that you must dial in your desired aperture prior to entering Live View mode, unless you're shooting with a PC-E lens. (This one lens type allows aperture changes during live view, but for all other lens types, the aperture value remains locked until you exit live view.) Note that unlike in the D7000, ISO sensitivity and shutter speed must always be controlled automatically during movie capture.

Regardless of the metering mode selected, movies will always be recorded using Matrix metering, with the Center-weighted and Spot options available only for still image capture. You can, however, adjust exposure compensation, and use the Autoexposure Lock button to lock the metered exposure, even after movie capture has already started. 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.

Nikon D5100 Video: Audio recording

The Nikon D5100 has an internal microphone comprising three holes located directly above the D5100 badge on the camera's front panel. As noted previously, the internal mic has a tendency to pick up camera handling and autofocus drive noise on the audio track of captured movie clips, with the severity of this likely varying significantly depending on the videographer, and the lens model in use. Thankfully, the D5100 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. Simply switching moving to a shoe-mount mic with some form of shock mount can do wonders for your DSLR audio, while moving the mic off camera at a distance can completely resolve the issue.

Another feature that can help resolve audio problems -- and one that's extremely unusual at this price point -- is the 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 D5100'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 D5100'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 D5100's Linear PCM audio is recorded with a bit depth of 16-bits, and a sampling rate of 48 kHz, plenty enough for good quality audio.

Nikon D5100 Movie Recording User Interface

The Nikon D5100's movie recording functionality is accessed from Live view mode. To start and stop capture, you simply press the red button adjacent to the still image Shutter button, while live view is active. You can control the aperture manually with the Mode dial in the M or A positions, so long as you select the desired aperture before entering Live View mode. With the Mode dial in any other position, movies will be recorded as if the Mode dial were in the Program position. Autofocus can be set automatically or manually both before and during movie recording, and if available on the mounted lens, 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.

The D5100 groups several settings related to video capture in a dedicated Movie Settings menu, accessed from the last page of the Shooting menu. It also offers limited in-camera movie editing functionality. You can select either a start or end point for a video clip, and save the resulting trimmed video as a new file, and it's also possible to extract single frames from a video. These functions are accessed from the Playback mode's Retouch menu.

Rolling Shutter Artifacts ("Jello Effect")

Essentially every video capable digital SLR currently on the market exhibits motion-related distortions called rolling shutter artifacts. These are caused because the image data is captured and then read off the chip sequentially by rows, rather being captured all at once. In the case of the Nikon D5100, with its variable frame rate, this means that image data for the last row of a given frame is captured and read out anywhere from 1/24th to 1/30th second after the data for the top row was captured. The effect on moving objects is similar to that of a focal plane shutter in an SLR, but more pronounced, because the video frame is read out much more slowly than the slit of a focal plane shutter moves across the sensor.

For a camera that scans video frames vertically (as all do that we're aware of), rolling shutter artifacts will be most noticeable for subjects that are moving rapidly side to side, or when the camera itself is being panned horizontally. Verticals in the scene will appear tilted to the right or left, depending on the direction of camera motion. As an example, consider the case of a camera being panned from left to right, with a flagpole or other vertical object in the middle of the scene when recording for a particular frame begins: If the top of the object was centered horizontally when the first line of the video frame is acquired, by the time the last line of the frame has been captured, the bottom of the object will have shifted to somewhere left of center: As a result, the vertical object would appear to be leaning to the right.

Computer Requirements for Viewing HD Video

A typical computer these days has little trouble dealing with still images, but high-definition video can be another matter. Depending on the file format involved, it can take a pretty beefy computer to handle HD-resolution video playback without stuttering or dropping frames. The H.264/MPEG-4 AVC image compression used by the Nikon D5100 is one of the more compute-intensive formats, and its 1,920 x 1,080 (1080p) resolution means there's a lot of data in each frame to deal with at full resolution. The net result is that you'll want a relatively recent and powerful computer to play full-res high-def video files from the D5100 on your computer. At lower resolutions, the requirements will be more modest. You can, of course, view your movies on a TV -- either via the composite A/V Output, or on an HDTV via the Type-C Mini HDMI output.