Pro shooters have come to swear by it and not at it — a remarkable achievement in itself for a complex electro-mechanical device. The Panasonic VariCam has earned its reputation as an industry workhorse, performing with great reliability while producing superb images under extreme conditions.
The camera's natural fall-off of image contrast and color saturation in the shadows has always been a notable advantage; its DVCPROHD 100Mb file size also proves more practical and manageable than other HD codecs on desktop workstations and servers. In many ways, however, the camera is still a work in progress. Indeed, low-light performance and noise issues have been addressed in the latest VariCam model — the AJ-HDC27H.
Basic setup
As is the case when working in the HD arena, the camera's setup requires a sufficiently large monitor (15in or more) to properly assess focus, detail level and colorimetry. My pet peeve with most HD cameras, including the VariCam for that matter, is the tiny viewfinder that fails to provide sufficient reassurance of focus during normal camera operation. It's only logical that the shooter/engineer uses a large enough monitor to see HD's higher resolution and what the heck he or she is recording.
The VariCam AJ-HDC27H permits instant changing of frame rate via a USER button on the side of the camera. Two assignable USER buttons are provided in VariCam models. Photo courtesy Panasonic. All other photos ©2005 by Barry Braverman.
The VariCam akin to most broadcast cameras features a dual filter wheel that should be positioned to reflect ambient lighting conditions. Tungsten (3200° K), daylight (6300° K) and mixed illumination (4300° K) settings are provided along with the usual exposure control filters: clear, ¼ ND, 1/16 ND and 1/64 ND. In general, shooters should use the strongest ND possible in order to achieve the widest aperture setting. This will help reduce the excessive depth of field condition as well as diffraction anomalies that lead to a significant loss of contrast.
The unit's claim to fame in many ways is its 720p imager, which allows variable frame rate flashing. This is a capability not found in cameras such as the Sony HDW-F900, which features interlace-type imagers. Variable frame rates from 4fps to 60fps in 1fps increments are selectable now in the camera via a USER button, giving the shooter additional flexibility in higher-end commercial and documentary production.
During my nearly 20 years at the National Geographic, I recall very few scenes (other than sync interviews) shot at “normal” 24fps speed. Shooting out of moving cars or capturing wildlife with long lenses usually demanded higher than normal frame rates just so subjects appeared normally paced on screen. In other words, the (film) camera's variable frame rate capability was not used solely, or even mostly, for slow-motion effects. The savvy shooter uses the camera's multiple frame-rate capability the same way — subtly, almost imperceptibly.
Setting exposure
In simple terms, correct exposure reproduces white as white, gray as gray and black as black. The shooter targeting a white or gray card typically adjusts the iris while referencing the camera's two sets of zebras. I usually set pattern 1 to 70 percent and pattern 2 to 98 percent. If you're confused by the jumble of diagonal lines covering the frame, you can disable the lower set; the upper pattern provides a reference to guard against clipping.
Gamma drama
Shooting in bright daylight at small f-stops can produce noisy low-contrast images devoid of life. Your camera’s exposure control filters can help by enabling a larger iris setting — an important strategy for VariCam and HD shooters in general.
The VariCam 27H features three gamma curves, two curves for film output and film-like video output, and the traditional video gamma. In the menus, one can select FILM REC mode, which at 9.5 stops of latitude is optimized for output to film scanners. The VIDEO REC gamma also incorporates the extended dynamic range of film while ultimately anticipating output to the video sphere. While some users will appreciate the VariCam's multiple gamma settings, most broadcasters will prefer the standard video gamma for live programs, including sports.
Independent filmmakers and shooters of narrative fare generally will opt for the gentle toe and heel characteristic of cine-look. The cine-look gamma produces more gradations of gray in the shadow areas, which can be desirable as it often adds life to the darkest areas of the frame. On the other hand, the same shadows, if severely underlit, may appear washed out or noisy when lifted in this fashion. For this reason, an on-camera fill or frontal wash should always be considered, especially when shooting close-ups of talent, because overly dark facial shadows may exhibit substantial noise and unusual hue shifts.
The same drill applies for black stretch. If black stretch is applied too aggressively, random noise may bloom in the shadows and wreak havoc throughout a production. Such defects may appear trivial on a set's production monitor, but single-pixel artifacts often are amplified and can become serious troublemakers during subsequent compression to DVD or satellite.
Grappling with noise
The AJ-HDC27H addresses the noise issue head-on (literally) as the new imager and block lowers the noise floor considerably. The model achieves this in part through improved heat dissipation through the front of the camera. It feels warmer to the touch at the front of the housing, which is reassuring. It means the camera's redesigned signal amplifier and beefier heat sinks are doing their job.
Panasonic also reduced the noise previously apparent in the blue channel when shooting in low light. This was one of my criticisms of the 27F; the camera lacked flexibility under such conditions. In the updated model, an alternative low-light algorithm is provided for shooting weakly illuminated scenes. Under most routine conditions, shooters will still want to stay with the VariCam's normal compression scheme. For the occasional challenging setup at low or no light levels, however, the alternative setting provides superior results.
There's another dimension to this noise discussion as well. The camera now incorporates a more precise 12-bit DSP (as opposed to the 10-bit version in the previous model), so sampling is more accurate, and a greater amount of highlight detail can be retained. This means that hot areas of the frame such as an exterior window are less likely to appear blown out as the oversampled detail is squeezed into DVCPROHD's 8-bit gamut. The additional detail helps reduce the risk of noise appearing in these areas.
As a VariCam shooter, you earn your stripes everyday. Make sure you understand what the zebras are doing in your camera.
More to gain
The camera allows a range of gain settings to boost (or reduce) the imager's analog signal. Levels of gain up to +30dB or higher (+36dB with super gain enabled) are possible albeit with dramatically increased noise that may negate any benefit derived in the first place from improvement in gray scale. Many shooters and engineers looking ahead to compression for DVD, satellite transmission or video on demand may want to use a negative gain of -3dB or even -6dB to suppress this shadow noise. But be careful: Blacks can become impenetrable at very low gain levels, so caution must be exercised.
A better and simpler approach in my experience is the use of a camera filter to lift dark areas of the frame. The Schneider Digicon or Tiffen Ultra Contrast filter can help transfer surplus highlight values into deficient shadow areas. In urban night scenes, the ultra contrast-type filter is one of the best things you can do to improve the look of your VariCam images. This applies as well to ENG-type footage frequently shot under such conditions.
Conclusion
Many noise-related improvements in the AJ-HDC27H have their roots in Restrictions On Hazardous Substances (ROHS), a recently adopted mandate that has impelled manufacturers to redesign products in accordance with environmental concerns. Fortunately, Panasonic used the opportunity to address key performance issues, most notably the lowering of the noise floor in the VariCam imager.
Barry Braverman is a veteran cinematographer with more than 20 years experience in feature films, documentaries and music videos. He is currently serving as a digital media expert and consultant to major studios. His latest book, “Video Shooter,” is available from CMP Books atwww.cmpbooks.com.
