By Matthew Jeppsen, January 21, 2009
I have long been an advocate of 35mm lens adapters. They are an effective way to add a whole new visual dimension to HD camcorder footage. But as with any tool, there are downsides. 35mm adapters add weight and length to a camera rig. They also aren’t very forgiving and must be set up carefully to deliver optimum results.
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The Nikon D90 offers an exceptional LCD screen
and impressive low-light capabilities.
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That’s why I was excited to learn this last fall that two DSLR manufacturers were introducing still cameras with video-capture capability. The Nikon D90 was introduced first, and it includes 720p HD video capture capability. Canon’s EOS 5D Mark II, with a 1080p mode, followed soon after. Both cameras allow you to use an incredible selection of lenses to capture video with a 35mm depth of field.
On the surface, these announcements are very exciting news. But what are the limitations and specifics of these new tools? Here, I’ll take an in-depth look at video capture on the less expensive of the two cameras, the sub-$1,000 D90.
Specifications
The D90 features a 12.9-megapixel DX-format CMOS sensor and offers a high-resolution 3-inch LCD on the back. As the sensor is APS-C sized, expect a 1.5x crop factor (18mm becomes 27mm, etc). Its full ISO range is 100-6400, so low-light capability is exceptional. Video is captured at 24p 1280x720, 640x424 and 320x216 resolutions. The compression codec used is Motion JPEG, and bit rate is limited to just under 16MB/s. Sixteen-bit mono, 11 kHz audio is captured from an internal mic. There is no external mic input. The D90 uses standard SDHC cards for storage, and video files come off the camera in an AVI container. Capture time is currently limited to five minutes in HD and 20 minutes in the other modes. Five minutes of HD video weighs in at about 600MB.
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The Good, the Bad, and the Ugly
The good news about the D90 is that this svelte little camera can capture beautiful video. With a sensor nearly identical in size to the RED ONE, depth of field is beautifully shallow. And the excellent lenses available for still cameras open up a world of creative possibilities. Early tests indicate that the D90 is capable of more than eight stops of dynamic range, which is not too shabby in HD-land. And for those highlights that do clip, it appears to roll them off smoother than many HD camcorders would. It doesn’t look as much like typical video as a result. The D90 is also rather good in low light. Yes, it can get grainy when the high ISO ranges kick in, but it’ll capture a usable image in low-light situations that would be nearly impossible for many HD camcorders even at high gain levels. Finally, there are extensive image tweaking controls available in the camera’s menus. You can define specific looks just as you would for still images.
The bad news is that the D90 offers almost no manual exposure controls. You can select the lens aperture, but there is no way to manually control the shutter speed and ISO (gain) settings. You can lock these settings down while shooting, but there’s no easy way to know exactly what they are, or preset them. Also, the camera’s form factor is not built for video shooters. You must hold the camera out in front of you, using the rear LCD screen to monitor and focus footage. On the subject of focus, get used to doing it manually. There is no auto focus on this camera when shooting video. Fortunately, the LCD is sharp enough to pull focus without too much squinting. You may want a hood or shade when shooting outdoors, however.
Another area of concern is the D90’s CMOS rolling shutter. Its readout is quite slow, and the shutter creates skew issues on moving shots. Rolling shutter means that the sensor is read from top to bottom, so the top of the video frame has been recorded a moment earlier than the bottom. Vertical lines moving quickly through the frame are therefore often rendered as diagonals. This includes panning across vertical lines. They lean, in effect, in the direction of the movement.
There is another side effect to the rolling shutter, and that is the aptly-named “jello effect.” Shooting handheld with the D90 reveals this instantly. It’s worth noting that these issues are not limited to the D90. All current CMOS-based cameras are susceptible to rolling shutter artifacts. The Canon HV20 exhibits both skew and jello quite clearly. It’s not hard to make the Sony PMW-EX1 show skew with a fast pan. Even the RED ONE has skew issues, seen in whip pans and quick dolly moves. The difference is that the D90 exhibits these artifacts significantly more than the aforementioned cameras.
All is not lost, however. There are a number of things that the shooter and editor can do to improve the D90’s shortcomings. Here they are, in no particular order.
Workarounds
1. Don’t shoot handheld. Seriously. Just don’t. I don’t care if your on-set nickname is Steadi-Eddie—you cannot hold this camera still enough to completely avoid its jello issues. Put it on a tripod, or at least a monopod, and your footage will look 100 percent better. That also solves another problem with this camera, namely, that its ergonomics are not designed for handheld video shooters. If you absolutely need handheld, third-party manufacturers—including Redrock Micro and Zacuto—are already offering support rigs for the D90.
2. Use the Auto-Exposure Lock function. Religiously. This is the little button next to the viewfinder marked AE-L. You cannot avoid this camera’s auto-exposure, but this button is your ace in the hole that allows you to lock in exposure settings on a scene. Now you can keep the camera from auto-adjusting the shutter and ISO in the middle of recording. I recommend that you set this button to act as a continuous on/off toggle under Timers in the Custom Menu.
3. Turn the in-camera sharpening settings all the way down to zero, which will eliminate some of the excessive jaggies in your footage. This is easily accomplished with the Set Picture Control function under the Shooting Menu. Note that you cannot be in Auto mode to modify presets, so switch to M for this task.
4. Pick up a handful of fast manual lenses. The 18-105mm kit lens for this camera is abysmally slow at f/3.5-5.6. Avoid it like the plague. Buy the camera body by itself and put your lens money into fast primes or a good zoom. An f/1.4 50mm, f/2.8 24mm, and f/2 85mm or 105mm will cover most shooting situations. The faster your lens, the less the camera will have to rely on noisy ISO. Ultimately you’ll have a cleaner image. Manual lenses also tend to offer an honest-to-goodness aperture ring, so adjustments are possible while shooting. And because auto-focus is not available when shooting video with the D90, there’s no real disadvantage to shopping for used manual glass.
5. Set the +/- exposure compensation settings to between +.03 and +2.0. The idea is that this range tends to guide the D90 into choosing slower shutter speeds, somewhere in the 1/30 to 1/60 range. This (in theory) helps keep the ISO settings low and noise at a minimum.
6. Shoot HD but deliver in SD. This camera is a far better SD camera than it is an HD camera. This is not to say that the D90 cannot deliver HD, but the downconvert hides some of the codec compression and the camera’s aliasing sins. As a good friend of mine often says, “It’ll clear up in the downconvert.”
7. In post, use the D90 Rescaler plug-in for Final Cut Pro on all your footage. This freebie from the Too Much Too Soon plug-in pack automatically fixes harsh horizontal lines in D90 footage due to its poor scaling algorithm. Get it at www.mattias.nu/plugins (and consider leaving a donation for the developer). There is also a plug-in for more intelligent up/downscaling.
Conclusion
The D90 is an odd bird. It is clearly a still image camera with a video mode tacked on as an afterthought. While there are a number of issues and limitations, it only takes a few minutes of shooting with the camera to realize the beautiful images you can create. With a little planning and care, you can minimize these limitations and maximize what this sub-$1,000 tool can do. It’s nowhere close to replacing my own 35mm lens-adapter rig, but the D90 may well have earned a place in my shooting toolkit.
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