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The Starting Point, Chapter 2008
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by Mark Schubin
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Imagine shooting someone against a window and being able to control the background brightness instantly without affecting the foreground. Imagine lighting a room with a 500-watt lamp aimed at the camera, instead of away from it, but still being able clearly to depict everything in the room, including the individual coils of the hot lamp filament. Imagine being able to shoot HDTV at roughly 7,000 frames per second.
Visitors to the annual convention of the National Association of Broadcasters (NAB) in Las Vegas last month didn't have to imagine these seemingly miraculous advances in acquisition technology, the beginning of the chain leading to television and video programming. They could actually see them, although in some cases only as visions of laboratory prototypes. Consider, for example, that 500-watt lamp.
It was shown at the opening session of the Society of Motion-Picture and Television Engineers (SMPTE) Digital Cinema Summit at NAB by Thomson's Dr. Peter Centen. First he projected a picture of just the lit light fixture, aimed at the camera. Those in the audience could see fine detail in the filament coils as well as the mesh of the safety glass in front of the hot lamp. But that might seem possible even with older cameras by using appropriate exposure and filtering, so Centen advanced to the next picture, one in which the lamp--still with fine filament detail--was visible at the lower right.
In old crime movies, there was often a scene in which a bright light was aimed at a person being interrogated, so the questioners couldn't be seen. If a person looks at a lit 500-watt lamp, he or she is unlikely to be able to perceive much behind it.
An electronic camera is similar. With a narrow iris, a short shutter speed, and/or neutral-density filters, it might show the lamp clearly, in which case all else would be essentially black. Or, with a wide iris, full exposure time, and no optical filtering, it might show many parts of the scene clearly, leaving the lamp a mere blur.
In Centen's image, however, not only was the illuminating lamp filament clearly visible, but so was everything else in the image, including toys, cereal boxes, a kitchen strainer, bottles of wine and cups (European research centers have excellent working conditions), and, perhaps most significantly, a test chart with gray scales and color strips on it, all behind the lamp. How was it possible for the Thomson laboratory imager to show both the hot filament coils and every shade of the grey scales--a range said to represent a contrast ratio of 10,000,000 to one, more than 23 stops of exposure latitude--in the same picture?
The answer lies in the ability of a CMOS imager to have on-chip control. Typically, an electronic exposure control--a shutter effect--is applied equally to all parts of an entire imaging chip (and, in typical prism-based cameras, to all three chips equally). If it's applied on a pixel-by-pixel basis, however, then brighter parts of an image can have shorter exposures than darker parts.
Centen showed only still pictures, so the audience couldn't evaluate what differing shutter speeds in the same image might look like when there is motion, and the imager being shown was just a laboratory prototype. The possibilities for increasing the dynamic range of cameras were nevertheless exciting.
Another panelist in the same session was Rick Robinson of Vision Research. For years, the company was considered by NAB show-goers, if they considered it at all, simply a manufacturer of high-speed cameras to be used only for motion analysis or other special purposes.
Vision Research remains a manufacturer of high-speed cameras, but the purposes to which they might be used now range to normal-speed digital cinematography. The company's previously introduced Phantom 65 camera, for example, has a top shooting speed of just 125 frames per second. Its imager resolution, however, is 4096x2440 (not counting on-chip color filtering, which Centen and Panavision's John Galt said reduce effective resolution).
That's slightly less than the resolution of the Red One camera (again, ignoring on-chip color filtering), but the Phantom 65's imager is much larger. The Red One's linear imager resolution (ignoring the color filtering) may be expressed as 93 line pairs per millimeter (lp/mm), slightly less than that of a typical 1080-line 2/3-inch HDTV camera's 100 lp/mm. The Phantom 65's similarly calculated linear imager resolution is just 40 lp/mm, making much lower demands on lens quality.
Robinson announced that there would be a lens-related announcement about the Phantom 65 when the show opened. Abel Cine Tech is now offering the Phantom 65 with Hasselblad lenses--lenses designed for some of the highest-resolution large-format still cameras. In the Abel Cine Tech booth on the exhibition floor, poster-sized photo enlargements offered show-goers the opportunity to examine the fine detail up close.
The Phantom 65 had been previously introduced, but at the Digital Cinema Summit Robinson announced a new Vision Research camera, the Phantom V12, which offers Vision Research's form of different exposures within a single image, called Extreme Dynamic Range (EDR). The Phantom V12 has a maximum resolution of 1280x800 (ignoring the color filtering), but at 1280x720 HDTV it can shoot roughly 7,000 frames per second, and at 1,000 frames per second about ten minutes can be recorded on a CineMag camera-mounted disk pack. At lower resolutions, the camera can shoot and capture images at a rate of a million frames per second.
What do such high speeds look like? NHK, the Japan Broadcasting Corporation, showed "live" examples in their booth with a million-frame-per-second camera of their own design operating at about 10,000 frames per second. A demonstrator pricked a water-filled balloon with a sharpened electronic probe. The probe triggered a recording sequence that was instantly played back at a normal video rate. Viewers could see the balloon's skin quickly peel back from the attack point, leaving a balloon-shaped blob of water suspended in mid-air, as though in a cartoon, before it finally fell in slow motion.
ARRI's Digital Cinema Summit demonstration involved different images of water, in their case a lovely mountain lake. This time the issue was spatial rather than temporal resolution. A 4K Sony projector presented imagery captured at 6K on an ARRIScan film scanner. For those in the front row, the difference between 65mm and 35mm film scanned and projected that way was clearly visible.
A version of the presentation, called "4K+ Systems," appeared in the April issue of the SMPTE Journal and is also available at ARRI's web site. Of particular interest might be the last figure, showing that, at a 90-degree viewing angle (hold the corner of a sheet of paper under your eye and its edges will offer an approximation), something that audience members in a movie theater could easily experience, 8K resolution is clearly visible (NHK also brought the latest, smallest, easiest-to-use version of their 8K camera to the NAB show). Some movie-theater audience members can probably perceive even finer detail.
The extraordinary dynamic range, frame rates, and spatial resolutions discussed at the Digital Cinema Summit might not be part of most videographers' immediate future, but there was plenty of new acquisition technology at the show that could be. Consider, for example, Rosco View.
It's not uncommon to shoot in a home, office, or storefront that has a window to the outside world. During the day, the daylight--and sometimes direct sunlight--streaming through the window can cause it to become a featureless blob in a video image. Perhaps someday Thomson's laboratory pixel-by-pixel exposure technology will be able to deal with the brightness differences between an interior room and broad daylight, but today it's common to put light-reducing filters on the window(s).
Unfortunately, after those filters are installed, someone might decide the window should look lighter or darker. Even if the decision on window brightness is set in stone, the earth isn't. As it rotates on its axis, the brightness of the window will change. Clouds can also affect the brightness. But it's almost impossible to change window filters between takes.
Rosco View is a two-part filter system. One part goes on the windows, just as any other filter would. The other part goes in front of the lens. Both are polarized.
If the polarizations are oriented the same on both the window and the lens filters, there's only a small light loss through each. If the lens filter's polarization is rotated 90 degrees from the window filter's polarization, essentially no light will pass from outside the window filter to the lens. In between zero and 90 degrees is a continuous range of light levels that may be adjusted simply by rotating the filter in front of the lens. Unless something between the window and the lens polarizes light, the rotation of the lens filter will have no effect on the foreground; it simply controls the window brightness seen by the camera (and doesn't prevent the talent from using window light for reading).
Want to simulate direct sunlight to test Rosco View? Mole showed a 24,000-watt HMI lamp. It'll put almost 120,000 footcandles into a 1.5-foot spot at a distance of ten feet (or almost 300 footcandles in a 30-foot spot at a distance of 200 feet).
Need camera batteries? Frezzi's nickel-zinc batteries outperform batteries with less environmentally friendly chemistries. And Toshiba previewed a lithium-ion battery line called Super Charge ion Battery. It's said to keep more than 85 percent of its capacity through 5,000 charge-discharge cycles, charge to 90 percent of capacity in just five minutes, operate at sub-zero temperatures, and not get too hot even with a forced short circuit.
How about an arm-based mount for handheld cameras? That's what Hoodman's WristShot is.
Need lenses with selective focus the way Thomson and Vision Research offer selective exposure? That what was shown by Lensbabies. Want Lenses for 35-mm-format digital-cinematography cameras (including ARRI's new D-21, Dalsa's new Evolution, and Sony's new F35)? Angenieux introduced the Optimo Rouge line for just that purpose. And, in the incremental war to one-up the competition, Fujinon bested its own HA22x7.8 HDTV lens with an HA23x7.6.
How about cameras with built-in lenses? Red's Scarlet is to offer a resolution of "3K for under $3K" with built-in 8x lens (the Red Epic, said to have 5K resolution--more than the Red One--was also announced); Panasonic's AG-HMC70 offers shoulder-mounted HD for under $2500 with a 12x lens and optical image stabilization; and Camera Corps offered a tiny HDTV camcorder with 10x built-in zoom light enough for a Polecam mount. Digit Tronics even offered, as a show special, a complete HDTV camcorder--with lens--for $299 (Aiptek has been selling even lower-priced models), and Ikonoskop offered a tiny, lightweight Super 16 film camera--with lens and film--for the "price of a DV cam."
There was much more to see in acquisition technology at the show, from stereoscopic 2K-resolution pairs of ice-cube-sized Iconix Video cameras with new controllers to new cameras and camcorders from all of the major manufacturers to a voice-recognition take-logging system from Horita. There were also interesting storage, processing, distribution, presentation, and test systems at last month's show, but for more information on those you'll have to wait until next month. After all, acquisition is only the beginning.
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