Nothing’s for Everything
In one scene of this season’s finale of the television series House, the only light appears to be coming from a flashlight in a character’s hand. The picture, nevertheless, is sharp and clear with a wide range of brightness and color, allowing detail to be seen even in the face of the flashlight holder, behind its beam.
The quality of the images was probably due, at least in part, to the way they were captured, with Canon EOS 5D Mark II DSLRs (digital single-lens reflex cameras), capable of acquiring HDTV images. Those cameras use one of the largest electronic image sensors, the size of a full-frame 35mm still image—twice the area of even 35mm motion picture film frames.
Bigger sensors mean greater sensitivity (ability to shoot in lower light levels without adding noise) and dynamic range (shades of gray that can be captured), wider angles, less loss of contrast and resolution due to diffraction, lower demands on lens quality, and more control over depth of field (how much appears to be in focus in the image). And it’s available for less than $2,500. So why do people continue to shoot HDTV with cameras that have smaller sensors and cost more?
One possibility is picture quality. Although the sensor in the 5D offers superb quality for still pictures, motion is something else. An electronic “rolling shutter” used to capture images, for example, can cause fixed upright lines like door frames and street-sign posts to seem to wave back and forth when the camera is panned rapidly. Vertical motion, too, can cause solid objects like tree trunks and mountains to vary their shapes.
There are also possible undesirable picture artifacts associated with the color-filter pattern placed on the 5D’s single image sensor. Video cameras using three CCD-type (charge-coupled device) chips tend to avoid both rolling-shutter and color-filter artifacts.
Then there are operational considerations. DSLRs are designed for shooting still images. Their microphones (if any) seem like afterthoughts, likely to pick up undesired sounds such as lens adjustments. Video outputs, audio inputs, standardized time code, shoulder mounts, focus-checking viewfinder controls and the like might all be built into video cameras. Some of those can be added to DSLRs with accessories.
Even top-of-the-line video cameras, however, are not appropriate for every application. For exceptional detail, NHK (the Japan Broadcasting Corporation) has developed cameras that can shoot images with 16 times more pixels than high-end HDTV; for motion analysis, they’ve also developed a camera that can shoot up to a million frames per second (HDTV in the U.S. has roughly 60 images per second).
Ultra high-sensitivity cameras can shoot a black cat in a coal mine as though it were a celebrity being hit with a spotlight on stage. Immersive Media’s camera systems can shoot 360 degrees around as well as up and down, all at once, and Germany’s Fraunhofer Institute has come up with one that can shoot panoramic arcs in stereoscopic 3D (below).
There are pill-sized camera systems—including lighting and transmission—that can be swallowed to reveal live pictures from inside a person’s alimentary canal. Mobile phone-based cameras, whatever their quality limitations, are always on hand. Exceptionally inexpensive cameras can be handed out to children.
No single camera is ideal for all purposes. But, as this season’s finale of House showed, sometimes extraordinary pictures can be made in unusual ways.