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USING PTZ CAMERA'S IN HOUSES OF WORSHIP

During the '90s, a couple of new technical trends began to converge in the broadcast industry. Robotic cameras, already familiar in the security business, started making their way into television studios. Remote-controlled camera pedestals and pan/tilt heads matched with shrinking ENG/EFP cameras enabled video engineers to extend their electronic control into what had been the cameraman's realm.

In the decade since broadcast-quality video and remote camera control began to merge, the hardware has continued to shrink while the control options have grown. Now, the Internet and IP control have allowed some of these devices to extend their range from around the building to across the planet.

PTZ cameras (pan/tilt/zoom) have exploded into a vast array of sizes and types, and their uses have expanded similarly. We will have a look at analog PTZ models and a few of the higher-performing digital PTZ types, commonly known as network cameras. The selections in our field have in common remote control of pan, tilt, and zoom functions, 30-frame transmission capability, and analog NTSC output or a maximum digital frame size up to at least 640×480 pixels. Although there is also a plethora of all-in-one videoconferencing systems available, we will examine PTZ camera models as discrete units.

REMOTE CONTROL

The primary distinguishing factor of PTZ cameras, as the designation implies, is remote control of camera movement and zoom. Analog PTZ models usually rely on an RS-232 or RS-422 control protocol through a multi-pin connector. The protocol used depends largely on the desired control cable length, with RS-422 capable of longer runs up to around 4,000ft.

A widely used control protocol is VISCA (Video System Control Architecture). This is a platform-independent machine control method developed by Sony that can be used to operate up to seven VISCA-compliant devices, such as PTZ cameras on a daisy chain of eight-pin RS-232 cables. Each camera is individually addressable by means of an identifying hardware switch or hexadecimal code assignment. Some models also permit various exposure modes and white balance to be set remotely with VISCA commands. These commands may also be used for controlling monitors, AV switchers, VCRs, and other devices. The protocol is open, and no licensing is required for distribution of VISCA-compatible hardware or software.

Some PTZ cameras also feature an auto-track function that will sense an area in the frame that is substantially different in luminance from the background and will activate the pan and tilt to allow the camera to keep that area in frame as it moves. It is wise, however, not to rely on this feature as a substitute for an alert operator.

Handheld, infrared remote controls are also a common accessory, enabling control from the room in which the camera is located. These are very handy for setup. With a local video monitor showing the camera output, one person can stand or sit in various locations and arrange the six or more preset shots with framing, focus, zoom, iris, and other parameters, using the IR remote.

Another spec that many PTZ cameras share is digital and optical zoom capability. As with any video camera with such features, the optical zoom does not noticeably diminish image quality, but the digital zoom, which on some models automatically engages at the end of the optical zoom range, rapidly degrades picture resolution. This is important to remember because the published zoom specification may actually be a combination of both optical and digital zoom ranges.

he PTZ controller interface may be hardware or software. If on-air shot changes are planned, it might be better to consider a joystick-operated hardware controller. A joystick controller is generally simpler to set up and operate than trying to perform smooth camera moves with a mouse. Most analog PTZ cameras can store six or more separate shots by memorizing the pan, tilt, zoom, and other parameters. Many offer a number of selectable zoom speeds. However, some PTZ cameras change shots with a rather jerky and mechanical movement, more like a security camera. This is one feature that should be evaluated with a first-hand demonstration before buying. For users considering computer control, software can be downloaded from most of the vendors' websites so that potential clients may familiarize themselves with the available options and get acquainted with the look of the graphical user interface.

PTZ FEATURES

PTZ cameras have adopted most of the features that one would expect to find on “prosumer” camcorders, including various exposure modes and shutter speeds, negative image, reverse video, and image flip for mounting the camera upside down on a ceiling. Some models also offer an “Auto ICR Mode” that switches on or off an internal infrared filter that's dependent on a luminance threshold setting. Under low light conditions, the IR filter can be set to cut off to allow better low-light viewing. Auto power-off may be set to a specific time period. Video muting is also available on some models, sending synchronous black on command.

There is a huge array of analog and digital PTZ cameras currently available. Most have the same basic features, but it pays to compare closely for those extra functions that will be just right for your specific application. With the current state of competition, it is important to know what's right for you. We can help you determine the appropriate camera solution to meet your needs and enhance your worship experience.