The Nikon D90

Credit: Nikon

At $995 for the body, the Nikon D90 will appeal to amateur photographers, and now, also to videographer wannabes.  However, it is too limited to likely get many serious looks from professionals.

The D90 is a “prosumer” level DSLR still camera with a DX-format (15.8x23.6mm) sensor.  The focal length multiplier is 1.5x for lenses designed for full frame 35mm.  The native resolution of the sensor is 4288x2488, or 12.3 megapixels.  Picture data is recorded to an SD or SDHC flash card, and can also be downloaded to a computer through a USB2 port.

The camera has the classic DSLR form factor, with an L-shaped body providing a large grip for the right hand, capped by a shutter release button.  The lens mount accepts most Nikkor autofocus lenses and teleconverters.  A hotshoe on top of the viewfinder housing gives the camera access to Nikon’s superlative line of external flashes, when something more than the built-in pop-up flash is needed.  The back is dominated by a large 3” LCD display screen.

The D90 has a decent ISO sensitivity range of 200-3200 at all resolutions, which can be extended to 100 or 6400 at reduced resolutions.  It has a 4.5fps burst framerate.  It can record still pictures in either compressed (JPEG) or raw uncompressed (NEF) format.

The most attention-getting new feature is the video capture.  The D90 is the first true DSLR to offer that feature, beating Canon to the punch by a scant month or so.  (Was it a knockout punch?  Hardly… read on.)

Video is supported only at a 24fps frame rate.  Video can be recorded as HD (1280x720 resolution at 16:9 proportions) or at 3:2 proportions (either 640x424 or 320x216 resolution).  The default resolution is 640x424.  The resolution can be selected in the Shooting Menu prior to recording.

To record video to the SD/SDHC card, one presses the “Lv” (Live View) button to the right of the LCD.  The mirror is raised, the viewfinder goes blank and the image from the sensor updates continuously on the LCD screen.  One then points the camera at the subject and presses the shutter button halfway to prefocus the lens using autofocus.  One then presses the OK button (in the center of the 4-way navigation control below the Lv button) to start recording video.  Pressing the OK button again will end recording of the video clip.

Once you enter video recording mode, autofocus is not possible; you must manually focus if the subject distance changes.  Only matrix metering can be used in video mode, manual exposure control is not allowed.  The exposure can be locked (using the AE-L button), or exposure compensation added to lighten or darken the video.

Audio is provided by a built-in monaural microphone.  This microphone is located a little above the lens release button on the front of the camera body.  One has to be careful not to cover up this microphone with the left hand.  The microphone tends to pick up operating and handling noises from the camera.  Unfortunately, it is the only source of audio provided; there is no external audio input jack, none at all.  (One can opt in the shooting menu for the camera not to record audio.  Audio could be recorded by external devices and combined with the video in an edit, outside the camera, but this is a pain.)

Video is recorded in Motion JPEG format.  This uses “intraframe compression” (each frame is compressed to the JPEG standard), and records a movie as a sequence of compressed frames.  But no “interframe” compression (spanning multiple frames) is applied, unlike in the more agressive MPEG encoding formats.  So video files will tend to be a little large.  Nikon does not specify the video data rate.

Audio is not compressed, it is kept in 16-bit linear PCM format, and merged with the video into a .AVI file.  Each clip is recorded in a separate AVI file.  The maximum clip duration is 2GB, or 5 minutes at HD resolution, or 20 minutes at SD resolution, whichever comes first.  (You can record multiple clips and combine them into a movie later, with video editing software, but that’s outside the camera.)
 
Because the D90 uses a CMOS sensor, with a rolling shutter, it is susceptible to several motion-capture artifacts.  If the camera is panned quickly, or if a subject moves rapidly across the field of view, the subject will appear to tilt (an optical illusion called “skew”).  If the direction of subject motion changes rapidly, as with camera shake when handheld, the skew will turn into a jellylike “wobble” of the image, which can be quite nauseating.  Under certain types of lighting (such as fluorescent or sodium-vapor) with pronounced flicker, dark banding artifacts might show up in images taken in this light.  Nikon warns of these problems, and recommends that a tripod be used (that will at least minimize the “jelly video” or wobble artifact).

Summary of key specifications and features:

·         15.8x23.6mm sensor (DX size)

·         4288x2488 pixels native resolution (12.3 megapixels)

·         Supports video resolutions of 1280x720, 640x424 and 320x212, all at 24fps

·         Motion JPEG video format recorded in .AVI file

·         Max video clip length is 5 minutes for HD and 20 minutes for SD

·         Max video clip file size is 2GB

·         Records to SD or SDHC flash card

·         Records audio from built-in monaural microphone

·         Outputs video to A/V or HDMI connectors for realtime display

·         Interfaces to computer through USB 2.0 port

·         Supports ISO 200-3200 at all resolutions, and 100-6400 at reduced resolutions

·         Has a pop-up flash, and a hotshoe for external flash

·         Has both an optical viewfinder, and a 3” LCD screen with live preview mode

·         MSRP (suggested retail price) is US $995.95

 

Strengths:

·         Access to broad Nikon line of lenses and flash units

·         Large sensor offers low noise and potential for shallow depth of field

·         Relatively inexpensive

 

Weaknesses:

·         No external audio input

·         Built-in mike is monaural only

·         Built-in mike picks up operating and handling noises

·         Severe rolling-shutter artifacts under certain conditions

·         No autofocus in video mode

·         No manual exposure control in video mode

·         24fps is only supported video frame rate

 

Comparing the D90 to other video options:
Compared to the Canon EOS 5D Mark II, the P90 lacks the full HD mode, and they run at different frame rates.  They both have very limited manual controls in video mode, however.  The 5D Mk II at least has an external audio input.  Both have excellent low-light response.  Both have access to superb lens systems and the potential for shallow depth of field.  The 5D’s sensor is larger, but the D90 still has a sensor almost the same size as a frame of 35mm movie film (which runs vertically rather than horizontally).

There is no comparison between the D90 and a real camcorder.  The camcorder wins handily.  The D90 might have an edge only in low light response, lens interchangeability, and shallow depth of field.

The D90 fares better in comparison with typical P&S cameras, most of which have very limited audio capability also, hopelessly wide depth of field, and no lens interchangeability.  In situations where rolling-shutter artifacts might show up, though, even a CCD-based P&S camera might work better.
 
The D90 is a very decent still camera.  But nobody should mistake it for a serious video camera.