The D3100 becomes the first entry-level Nikon to feature live view, and in some ways its implementation feels distinctly entry-level too. The lever to enter and exit live view is a nice touch, though, as it's well-placed for operation by your thumb, and on the plus side live view can effectively give you access to two 'missing' features, in the shape of depth of field preview and mirror lock up.
Live view contrast-detect autofocus offers a range of modes, from face detection to the ability to target AF to a specific point absolutely anywhere in the frame, and including the new AF-F mode that attempts to track a subject continuously around the frame. Focusing is fast by DSLR standards (certainly much quicker than any of the Canon Rebel series), but still lags distinctly behind what we're now used to from mirrorless interchangeable lens cameras such as the Panasonic G series.
In the PAS shooting modes, the live view image will darken or brighten to reflect any exposure compensation you set, although sadly there's no live histogram to help judge the optimum exposure. In M mode, though, the display makes no attempt to reflect the currently-set exposure level at all. To compound this there's no exposure meter display, so you have to switch to the control panel by a press of the 'i' button to check your exposure (temporarily exiting the live view display in the process).
Magnification of the Live View display is available in 5 steps, but disappointingly this appears to be nothing more than a crude up-sampling of low-resolution sensor output (as opposed to 'zooming in' to a high resolution output to show more detail). As a consequence, the magnified display is a relatively poor aid to achieving critical manual focus. This is unfortunate, as a well-implemented focus aid in live view could have made non-AF-S lenses much more useable.
One genuinely useful characteristic is that, like the D7000, the D3100 holds the mirror up all the time in live view mode, and doesn't have to drop it down to reset the shutter and make the exposure. As a result, you can use live view as a proxy for mirror lockup to minimize vibration when shooting off a tripod, in concert with either the remote release or the self timer. Simply enter live view to flip the mirror up, then release the shutter a couple of seconds later when any vibrations have died away.
The D3100's Live View aperture control behaviour also shows an odd quirk that first appeared on the D300. When you enter Live View, the camera will stop down to the currently set or metered value (offering an undocumented depth-of-field preview in the process), but what it won't then do is readjust the diaphragm 'live' if you change the aperture setting. It will honour the set aperture when actually making an exposure, and indeed return to live view at that aperture afterwards; alternatively you can force it to readjust by exiting and re-entering live view.
This behaviour is, simply, a bug, rather than some fundamental limitation of the F-mount; the D3 series bodies can continuously adjust aperture in live view, exactly as you'd expect. And it does have a couple of practical consequences - it can give a misleading impression of the depth of field you'll end up getting, and it further complicates manual focus as you have to remember to always initiate live view at an appropriate aperture (normally with the lens wide open). Also, in lower light conditions the display can appear dark and/or grainy if you enter live view with the camera set to a small aperture. As we'll see later, this bug has a curious knock-on effect when shooting movies too.
Overall, the D3100's Live View is certainly quite functional as a basic means of framing for stills and video shooting, and to its credit has unusually good autofocus for an SLR. However it lacks many of the more advanced features you'll find on more expensive SLRs, or full-time live view cameras such as the Sony NEXs or Olympus Pens.
The D3100 is the first (although no longer the only) Nikon DSLR to offer Full HD (1080p) movie recording. Unlike most other SLRs at this price level, the basic video controls are integrated neatly into the overall design - movies can be shot in any exposure mode simply by engaging live view and pressing the dedicated record button (there's no need to set the camera to a specific movie mode).
The D3100 gives a choice of three video resolutions - 1920 x 1080 Full HD, 1280 x 720 HD, and 640 x 424 SD - which all use progressive (i.e. non-interlaced) frame recording. Files are encoded in the .MOV Quicktime format using the currently-standard H.264 compression. Nikon's choice of the .MOV format makes the files sharing-friendly for playback on computers or uploading to the web, but does mean they can't be recorded directly to DVD without conversion (unlike AVCHD).
The built-in internal microphone captures mono audio only, and there's no facility to connect an external unit. You can choose to turn sound off during recording, but beyond that you have no control over it at all (there's no recording volume control or wind-cut option). Some basic video editing options are available in-camera via the retouch menu, allowing you to trim clips to selected start/end points, or extract individual frames as still images.
|Sizes|| 1920x1080p: 24 fps
1280x720p (HD): 30, 25 or 24 fps
640x480 (SD): 24fps
|Audio recording||Built-in Mono Mic, Linear PCM encoding|
|Max file size per clip||4GB|
|Max running time per clip||Approx 10 min|
Using Movie Mode
Movie shooting is relatively well-integrated into the D3100's control system: simply engage live view using the large lever on the back, then press the red button at its center to start recording. At this point the live view image will crop down to the 16:9 aspect ratio if you're recording HD footage - sadly though there's no way to preview in 16:9 for more accurate framing before you start. You can record a still image while shooting a movie simply by pressing the shutter button - however this does also stop movie recording.
Shutter speed, aperture and ISO are usually set automatically, and you can press the AEL button during recording to lock the exposure. In the PAS modes you can apply exposure compensation up to +/-3 EV, either before or during filming. In A and M you can also control the aperture the camera uses for filming - although due to the bug described in our Live View section, not in the way you might think (or indeed the manual suggests).
The crucial point to remember is that the camera enters live view at the currently set (or metered) aperture, but then remains there no matter what changes you make, until you either exit live view or take a picture. This means, bizarrely, that movies aren't always recorded at the currently-set aperture. For example, if in A mode you set the camera to F5.6 and enter live view, then change the aperture to F16 and start recording, your movie will be shot at F5.6. But if you then take a still image and restart movie recording, your new clip will now be shot at F16. This is, obviously, somewhat confusing until you understand what's going on - at which point it's merely inexplicable.
The lack of a hinged screen on the D3100 makes movie shooting a little more awkward than with cameras such as the D5000 which offer this feature. Like all DSLRs, its ergonomic design (including the grip shape and button/dial placement) is distinctly optimized for working with the viewfinder to your eye - something that's not an option when shooting movies. The D3100 essentially forces you to shoot hand-held footage with the camera held out in front of you so you can see the screen, which isn't a particularly comfortable or stable way of working.
Movie mode displays
|The movie menu is pretty basic - you get to choose resolution/frame rate and whether or not to record sound, but that's your lot.||There is a choice of movie sizes and frame rates available. The full HD 1080p mode is only avilable at the supposedly 'cinematic' 24 fps.|
Video quality comments
On the whole the D3100's movies are really rather good, with smooth motion and impressively low noise in dim light. The sound quality from the built-in microphone is quite acceptable for casual shooting, but nothing to write home about. In quiet situations, though, it will easily pick up noises from camera operations - zooming, or autofocus in AF-F mode, so you may wish to turn sound recording off in such cases.
Like all DSLRs the D3100 can suffer from 'jello' effects when panning or recording subjects that are moving fast across the frame, with vertical lines tilting to diagonals due to the use of a 'rolling' shutter. However you have to pan pretty fast to really see it, and it's not at all likely to be a serious problem in normal use.
Predictably enough the internal microphone will tend to record the sound of the lens focusing and, though it can be drowned-out by the sound you were actually hoping to record, the lack of external option means it's something you'll have to live with.
The D3100's AF-F continuous focusing mode has to count as a qualified success - in the samples below you can see it twitching in and out of focus, and occasionally failing to establish the correct focus for a second or two on what is a relatively undemanding subject. Obviously it's better then not being able to refocus at all, which places the D3100 ahead of any other entry-level DSLR in this regard. However it can't match its morrirless competitos such as the Sony NEXs or Panasonic G series, substantially becuase these have lenses specifically designed for the job.
The focus tracking mode (in which you specify the subject for the camera to track, based on color) helps to reduce the focus hunting a little because the camera has a clearer idea of what it's meant to be keeping in focus. However, it is easily confused and will regularly 'lose' its subject, particularly if it moves too quickly, so don't get your hopes too high that this is the camera to shoot Hollywood-standard movies of exuberant children.
Caution: very large files
Sample video 1
|1920 x 1080p 24 fps, MPEG-4/AVC, .MOV file, 17.4 sec. 40.6 MB|
Sample video 2
|1920 x 1080p 24 fps, MPEG-4/AVC, .MOV file, 7.5 sec. 16.5 MB|
Sample video 3
|1920 x 1080p 24 fps, MPEG-4/AVC, .MOV file, 8.6 sec. 19.6 MB|
Sample video 4
|1280 x 720p 30 fps, MPEG-4/AVC, .MOV file, 5.2 sec. 7.2 MB|
Sample video 5
|1920 x 1080p 24 fps, MPEG-4/AVC, .MOV file, 3.5 sec. 4.8 MB|