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BenQ Knowledge Center

The Myth of High Contrast

BenQ
2020/03/02

With the growing availability of high-end technology coupled with the explosion in quality content in recent years, the consumer electronics market has seen a corresponding uptick in the pool of sophisticated buyers. With knowledge gathered from a wide array of sources, these consumers have shown a discerning eye when picking and choosing their next purchase. For some, though, this has led to a single-minded focus on product specifications and the numbers used to express them. In the home theater market, and for projectors particularly, one such number that many consumers have increasingly latched onto is contrast ratio. The basis for this fascination with contrast is the idea that the higher the contrast ratio, the more precise the projector’s images are thus allowing viewers to see more detail in the projected image.

The question to ask then is whether contrast ratio is a good overall indicator of image quality, and if so, what is an ideal contrast ratio for your projector.

FOFO Contrast & ANSI Contrast

Before getting into the debate regarding the adequacy of contrast ratio we must first help define the two types of contrast ratios that are considered relevant for projectors: Full-On and Full-Off (FOFO) contrast and ANSI contrast.

FOFO contrast is simply the ratio between the brightness of a solid white reflected image from a projector and the brightness of a solid black reflected image from the same projector. For instance, a projector with a 2000:1 FOFO contrast ratio means that the solid white image is 2000 times brighter than the solid black image.

ANSI contrast measures contrast in a different way, it uses a checkerboard pattern of eight white and eight black squares and measures the ratio between the average brightness of the white squares and the average brightness of the black squares. The underlying principle behind ANSI contrast is that audiences almost never view images that are solid black or solid white (as with the images used to measure FOFO contrast), instead they view images that have countless gradations of brightness across the frame. In such circumstances the light from brighter sections of the image undoubtedly mixes and blends with the dark sections of the image. ANSI contrast therefore tries to express this reality with its simultaneous use of white and black boxes.

In terms of actual numbers, FOFO contrast ratios for projectors tend to float around the thousands-to-one, while ANSI contrast ratios tend to be in the hundreds-to-one. Given the average consumer’s tendency to equate higher numbers with being “better”, most brands have favored the use of FOFO contrast ratio in their contrast specifications.

Native Contrast & Dynamic Contrast

Most projectors on the market include features that help them make adjustments based on the projected image. These may include features such as dynamic irises, which “shrink” the projector’s iris when projecting a dark scene thereby making the blacks blacker, or lamp/picture modes that help dim the overall brightness of the lamp. While these features provide overall benefits to the user by ensuring that at every moment the projector is providing the best visuals it can, many times these features also help inflate FOFO contrast numbers. This is due to the fact that when measuring FOFO contrast these features can be enabled while measuring the solid black screen and then disabled for the solid white screens, but in reality when these features are employed on individual scenes they affect the brightness of all the shades shown in the scene and thus have a minimal effect on contrast. To reflect this reality many manufactures have distinguished between native contrast, which is contrast measured free of the use of such features, and dynamic contrast, which is the contrast measured with these brightness features active.

More light output during bright scenes

Less light output during dark scenes

Measuring Projector Contrast

As contrast ratio falls under the realm of optics, its measurement, as with any other science, requires precision and care to ensure accuracy in its readings and results, For instance when measuring ANSI contrast even the color of adjacent objects, including the clothing on lab personnel, may influence light readings, thus readings are commonly done with robotic arms and sensors.

Measuring projector brightness with a light meter

Contrast measurement with contrast sensors

Are High Contrast Ratios Misleading?

High contrast ratios might be misleading

Because of the market pressures described in the opening paragraph, brands have increasingly felt the need to push for more eye-popping specifications and higher contrast ratios for their projectors. As a result, many brands use dynamic contrast ratios to promote their projectors, because dynamic contrast ratio numbers on scale tend to be drastically larger than native FOFO contrast ratios and ANSI contrast ratios. But again, these ratios are misleading in the sense that in a normal setting the average consumer will probably not use the features which the dynamic contrast ratio numbers are built upon while watching videos with their projector. Given this, the dynamic contrast ratio that is measured using a projector’s auto adjustment features and then advertised in the marketplace might never actually be realized in practice.

What is the ideal contrast ratio for a projector?

Keeping in mind all that has been described above, what then is the ideal contrast ratio to look for in a projector?

Our answer to this question is not that simple, we suggest that you do not get caught up in specs. For projectors, contrast ratios only tell one side of the story and what it tells might not be entirely accurate. To produce the type of crystal-clear images that knowledgeable consumers are looking for, a projector not only needs to have good contrast, but it also needs to complement that contrast with optimal color performance. A focus on contrast ratio alone is a one-dimensional gamble. Only projectors that have been professionally calibrated to authentically reproduce the entire color spectrum can achieve the level of detail that is needed to give a viewer a full visual experience.

Less light output during dark scenes

Conclusion

To ensure that your projector meets the standards described above, we strongly recommend that consumers take a holistic approach and experience a live demo of any prospective purchase to test its overall performance. If an in-person demonstration is not possible, we suggest doing as much research as possible, checking out online reviews to find out about what others think of the product. Additionally, the color accuracy takes a big part of image performance, and BenQ even makes the final reports from their color calibration available to consumers. Again, the best thing to do is to avoid zeroing in on specs to make sure you get the most out of your purchase.

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