We’ve all seen it. A seminar presentation with slides that are difficult to read, or the big game on a projection screen at a bar looking washed out.
InfoComm has addressed this common, but often overlooked, problem. Collaborating with some of the brightest (pardon the pun) minds in the video market, the trade organization has developed and released its Projected Image System Contrast Ratio (PISCR) standard.
InfoComm says the standard defines projected image system contrast ratio, and its measurement. It covers installed systems and live events, and applies to front- and rear-projection systems.
The group emphasizes the standard encompasses four contrast ratios based on content viewing requirements, and the term system contrast ratio refers to any image that is presented in a space with ambient light. A key component of PISCR includes metrics to measure and validate the performance criteria defined by the standard.
The Purpose of PISCR
InfoComm says the standard was developed to define minimum contrast ratios for projected images. Focusing specifically on contrast levels, the standard does not incorporate provisions for the testing and measurement of luminance, image size, display resolution or other attributes.
InfoComm notes, “contrast is further qualified as ‘projected image system contrast ratio [PISCR]’ because the individual performance factors of the projector and screen are only contributory factors to the delivered contrast ratio of the installed system. It is also termed as ‘system contrast’ ratio because the maximum contrast ratio a projector and screen can deliver is ultimately affected and thus determined by ambient light.”
The standard divides into four categories that each call for minimum requirements:
- Passive Viewing: Viewers are able to see images on a screen and can distinguish text or a main image from the background during typical lighting within the room or environment. Passive viewing requires a minimum contrast ratio of 7:1.
- Basic Decision Making: Under this term viewers can make decisions based on displayed images. InfoComm says decisions are not dependent on critical details within the image, but there is “assimilation and retention” of the presented information. For this requirement viewers are engaged with the content in environments such as classrooms, boardrooms and multipurpose rooms. Minimum contrast ratio is 15:1.
- Analytical Decision Making: Ramping up the requirements of the Basic Decision Making spec, this requirement states that viewers must be able to analyze details within the image. It also states that viewers are engaged with the content; InfoComm cites applications such as medical imaging, architectural/engineering drawings, forensic evidence, and photographic image inspection as a few examples. Minimum contrast ratio is 50:1.
- Full Motion Video: The final specification requires viewers to be able to discern key elements within full motion video. Some of this detail includes points critical to a storyline and the overall intent of the video. Among applications InfoComm points out are home theater, business screening rooms and broadcast post-production. Minimum contrast ratio is 80:1.
Note that the standard does not apply to flat-panel displays regardless of what technology they employ (LED, LCD, plasma and OLED), as well as CRT. PISCR also doesn’t apply to reflective technology displays such as “electronic paper.” InfoComm adds the standard defines contrast ratio as a relative metric; it does not prescribe to black or white luminance levels.
Regarding the testing procedure, InfoComm says dealers must use PLUGE (picture line-up generation equipment) patterns to set proper black levels, and a grayscale pattern to set white levels. Measurements should be done with a 16-zone black-and-white checkerboard (inter-frame) pattern.
To measure the checkerboard pattern dealers must use a photometer (luminance meter or spot photometer with up-to-date calibration) that offers a spectral luminance response of the standard observer with photopic vision defined in CIES002. Other items required for testing include a measurement form, tape measure or rangefinder.
InfoComm also requires a Viewing Area Plan that includes multiple viewing locations, and measurements must be taken from five locations. After testing, there is a tiered verification system: Conforms, Partially Conforms, and Failed To Conform.
Why the Standard Is Important
So why should the commercial AV industry and integrators care? Joel Silver, president and founder of the Imaging Science Foundation (ISF), says PISCR facilitates the promise of performance. Silver says dealers installing projection systems into schools, boardrooms and other environments need to train clients on what to expect from the standard, how their systems are designed to meet the spec, and that their systems have been documented to show compliance.
“I think this is good, solid business,” he says. “It’s a good business plan when you walk into their facility, you make them happy and then you take the check.”
Beyond the practicality of PISCR from a business perspective, Silver says what makes the standard dealer friendly is that it is based in science and approved by InfoComm and ANSI (American National Standards Institute). He emphasizes the standard is a free resource that still isn’t well known, but once integrators subscribe to and learn it, they will be able to deliver better performing systems.
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