START WITH THE SOURCE
The start of the signal chain in an IMAG system isn't your video cameras, it's the light coming off the objects/people you want to capture. And that light comes from the lighting fixtures used in your auditorium.
“There are two primary concerns when lighting a stage for video,” says Lighting Designer C. Andrew Dunning of Landru Design in Nashville, Tenn. “These are color and contrast. Both of these have to do with the limitations of video cameras. The human eye can deal with infinite color temperatures all at the same time, as well as deep shadows and strong highlights.” But video cameras cannot.
Color temperature refers to the color makeup of the light being used. Tungsten lighting (which is what's in your typical theatrical lighting fixtures) tends to be rather yellow; fluorescent lighting is a bit green; arc-source lighting is rather blue. While our eyes and brains can deal with different color temperatures implicitly, video cameras need to be told what color temperature lighting they are “seeing” (or what color “white” is), so that they can accurately record the colors of the image. If you're ever noticed photographs that look very blue or very yellow, that happens when the camera is set for the wrong color temperature. When this happens, skin tones look wrong, and the video looks terrible.
“In an ideal world, all your lighting would be of the same color temperature,” Dunning adds. “In the real world, get things as close as possible without alienating the audience. If you're using a lot of moving lights that have arc-source lamps, color-correcting Tungsten up to the arc source color temperature would alienate the audience because it looks very cold and harsh. So, try to find a happy medium. Color correct your arc-source and video projectors down towards Tungsten, and correct the Tungsten up towards the arc source, and meet somewhere in the middle.”
Additionally, video cameras can't deal with a lot of contrast between the shadows and highlights. “The steeper the angle of your lighting, the more shadows on facial features will be created that are hard for the camera to capture. Minimize shadows and dark spots on the stage,” Dunning says.
Other lighting considerations are the quantities of light on the platform. The lower the lighting levels, the better cameras and lenses you are going to need, and the better your camera operators need to be. Low light levels mean you need to open the iris of the camera more to get more light into the camera; the larger the iris opening, the shallower your depth of field, which can result in more dramatic on camera images.
The trade-off is that camera operators have to work harder. With the iris wide open, having your pastor move just a few feet towards or away from the camera may put them out of focus. The more light you have on stage, and smaller the iris can be, and the more leeway your pastor has to move without your needing to adjust the focus of the camera following him or her.
“I've found front-light levels in the 50-60 foot-candle range to work quite well,” suggests Dunning. “And for long events, more light may be needed to not exhaust your camera operators. One of my colleagues produces multi-day, in-the-round events and wants 80-90 foot-candles so that the camera operators won't be quickly exhausted by intense concentration.”
VIDEO CAMERAS
Once you have light, you need video cameras to capture the images on stage. What level of camera you need depends on a variety of factors.
“There are several considerations when choosing an IMAG camera,” states Jason McKelvey, an A/V consultant with Acoustic Dimensions in Addison, Texas. “First, does the pastor or presenter move, or do they stand behind the podium? If the church can confidently say that the speakers will be stationary, then the requirements drop dramatically. When you have a moving target, the level of quality needed for the camera (and tripod and operator talent) increases for several reasons.” And this level of quality isn't found in your consumer video cameras found at the local big box retailer.
“First,” McKelvey continues, “a small consumer camera will not have the studio-configured rear zoom and focus controls necessary for smooth operation. Second, a consumer camera will not have the mass to keep a smooth, stable shot while panning and tilting. And third, most churches will not have the large lighting system necessary to obtain even lighting across the stage. This necessitates a camera whose iris can be controlled with a CCU (camera control unit) and RCP (remote control panel) to allow a remote engineer to control iris functions as the presenter walks in and out of dark spots on the stage.”
The person who would operate the CCU system is referred to as a shader. “The purpose of a shader is to remotely control each camera's lens iris for proper exposure during an event or service,” states Dave Cooke, chief engineer at Willow Creek Community Church in South Barrington, Ill. “The shader needs to adjust the camera iris as stage light levels and camera framing changes before the video director takes the camera live to the screens. Doing this remotely allows the camera operator to concentrate on focus, zoom and framing camera shots, with no need to worry about exposure settings.
While the CCUs main purpose is to allow the shader to adjust the iris, it also has other functions. “The CCU also allows for an engineer to ‘paint' each camera to the stage lighting and match each camera's color balance to the other cameras in the system,” Cooke adds. “Doing so allows for perfectly matched cameras. These paint settings can be saved and recalled from the CCU. The CCU also provides power and intercom to the camera head and also provides an array of video connectivity at the CCU location for easy wiring and integration into the video system.”
Another consideration is whether you want to use multiple cameras.
“Consumer cameras will never match in image quality completely,” says McKelvey, “and lack the features that allow you to adjust the images to match as closely as possible. For multiple camera systems, you are leaning toward a broadcast camera system with studio-configured cameras. A budget studio configuration with rear controls, large viewfinder, and lens can retail at $20,000 for a 1/3-inch broadcast lens and go as high as $150,000 (and everywhere in between). But the difference in performance and image quality are dramatic.”
When buying your camera, don't purchase sight-unseen. Make sure you demo any camera to make sure you'll be satisfied with it. Often you can get a demo unit in for evaluation at your location. If not, attending a show like National Association of Broadcasters (NAB) in Las Vegas will let you get your hands on any camera you're considering.
CAMERA SUPPORTS
Once you have your camera, you need to have a support system for those cameras. Your main “money” shots will need to come from a system that's stable—not delivering “shaky-cam” shots that you get from a handheld camera.
“By utilizing a camera platform of one type or another in preference to hand-held, you gain control of all motion—be it pan, tilt, elevation, tracking, zoom or focus,” says Peter Harman, product manager for Vinten, a manufacturer of camera support equipment based in the united kingdom. “For basic pan and tilt shots or relatively predictable situations, a tripod system is all that is needed. A lightweight tripod system provides portability if quick repositioning is necessary; a heavy duty tripod is good if the camera is likely to remain in the same spot for the duration of the production. However, if the camera needs to keep up with the movement or the production would benefit from more creative movements to tell the story better, a pedestal system would be beneficial. However, pedestal systems need space to allow them to operate and they need a flat, level and stable floor if you want to get the very best out of them.”
Additionally, Harman says that when selecting a tripod, counterbalancing systems to ensure the camera remains stable at any angle of tilt is important, and fluid movement of the head is critical for smooth camera movements. If the head sticks when you first start to move it, or doesn't provide enough drag while moving, the camera movements can be jerky and result in poor camera shots.
McKelvey adds that a quality tripod system designed for IMAG can range from $500-$15,000.
CABLING
Once you have an image being captured by a camera, you need to get that signal to your switcher and projectors. There are several options in common use, depending on whether you are doing standard-definition or high-definition.
“There are a few approaches to getting your video signal to the projector,” states McKelvey. “First, there is no future in standard definition (SD), so even if we are retrofitting a system that will retain SD equipment, we never invest in antiquated technology. Instead we will specify HD-capable cabling, which will handle any SD signals.”
There are several options for HD-capable cabling. “Fiber optic is the most future- proof option available at this time,” states McKelvey. “It can handle any signal with the right transceiver pair. We use a six- strand bundle. Be sure to know whether your transceivers use multi-mode or single- mode cable.”
Single-cable coax cable is another option. “A good 75-ohm precision video cable (16 or 18 AWG) coax can run composite, HD- SDI or even 3G-SDI,” McKelvey adds. Each signal type has distance limits over coax, so be careful not to exceed those limits.
For short computer signal runs, McKelvey says that a bundled five-conductor (RGBHv) coax cable can be a good choice. The resolution of the signal and cable gauge affects how long the cable run can be.
And lastly, CAT5 extenders can be a great way to extend computer signals. “There are extenders for analog computer signals and DVI, and [they] can save a lot of money over buying long, high-quality, bundled coax cables. Some models have receivers with skew compensation to fix the color shift problems that can occur over long distances,” states McKelvey.
“No matter which you choose, always run an extra CAT5 cable that can be used for control of the projector, although some ex- tenders allow RS232 control to come along for the ride on the same CAT5 as the video signal,” McKelvey concludes.
SWITCHERS
Unless the only thing you're going to display on your screens is the output of just one video camera, you're going to need some sort of switcher to select what input signal will be routed to your projectors. Some switchers require exactly the same type of video signal to be used at each input; others provide scaling capabilities to allow different format signals to be converted by the switcher and mixed together without any visual artifacts.
“The switcher/scaler is by far the best answer to IMAG,” states Christopher Bragg with Messenger Media Systems in Atlanta. “The main requirement for an IMAG switcher is a very low frame delay. If the switcher delays the video source significantly, then the end result could seem like an over-dubbed foreign film. Many low-cost switchers take a long time to process the video correctly and will have seven or more frames of delay. When combined with the delay in other pieces of equipment, this could, in extreme cases, add as much as a half-second to the output of the switcher.”
This much delay is highly noticeable to the congregation, and highly distracting.
“Because many other aspects of the IMAG system can introduce delay,” continues Bragg, “it is incredibly important to have the fastest processing available.”
Bragg adds that another important feature of the switcher is the ability to generate test patterns to facilitate projector calibration to achieve accurate colors, contrast and brightness. “If an image is not calibrated then the pastor could look washed-out or sickly on the screen, losing facial detail and having the end result be distracting instead of enhancing the worship experience,” he says.
For an HD system, Bragg recommends a switcher that can accept HD-SDI signals. “Many times a high quality HD camera will have an uncompressed HD-SDI output. A switcher/scaler can then take that signal without any conversion and send it out via HD-SDI to a projector with an HD-SDI input card. This would allow the video image to travel from end to end of the system without being compressed, converted or degraded. If HD-SDI is not supported then other digital signals are desirable, such as HDMI or DVI.”
PROJECTORS AND SCREENS
The final stop in the video signal “food chain” is the video projector and screen. And thanks to the improvements in projection technology over the last decade, this isn't as complicated a decision-making process as it once was.
“Most of the projectors that are usable in a large venue are good for IMAG,” states Pete Putman, CTS, president of Roam Consulting LLC based in Doylestown, Pa. “Ten years ago they were just concerned with getting a bright enough image on the screen,” he says. “This isn't an issue any longer.”
Putman says the needs for IMAG aren't really any different than the needs for any other type of video. Look for projectors and screens that provide accurate color rendering, good dynamic range that provides deep blacks through bright whites, consistent white balance at any level of gray, and consistent brightness across the screen.
For rear projection situations, look for a screen that provides a viewing angle that works for your room and the brightest image with minimal hot-spotting. The screen should also provide a neutral color temperature—it shouldn't alter the colors of the image being projected.
In front-projection situations, most any screen will do, according to Putman. “What's gotten better is the projectors themselves,” he states.
“Basically, your live video should look just as good as any other type of video,” Putman summarizes.
