Contrast Ratio is one of the primary specifications to look for in a projector. Many buyers base their purchase on the brightness ratings and contrast ratios of different devices. However, it can be equally confusing as the contrast ratio values of projectors range anywhere from 100:1 to 500,000:1. Knowing various methods used for calculating contrast ratio values and understanding the impact of contrast ratio on picture quality can help buyers choose the better projector out of the available options.
What Is Contrast Ratio In A Projector?
Contrast Ratio defines the ratio of the whitest shade of white to the blackest shade of black that a projector can display. When explained in simple terms, if a projector has a contrast ratio of 2000:1, it implies that the whitest shade it can show will be 2,000 times brighter than the blackest shade it can project. A higher contrast ratio denotes that the projector can project darker shades of blacks and brighter shades of white. It will make the picture more detailed and improve its clarity and quality.
Types of Contrast Ratio Ratings
Projector manufacturers may specify various contrast ratio ratings for their devices. It can be pretty confusing for the buyers as these values are very different. Some models may list a contrast ratio of around 1,000:1, while others have a contrast ratio upwards of 100,000:1. However, these values are not directly comparable. There are broadly two types of contrast ratio ratings – full on/off contrast ratio and ANSI contrast ratio.
Full On/Off Contrast Ratio – Full on/off contrast ratio is popularly used by manufacturers but is inaccurate and misleading. It is calculated by first projecting a solid white screen (100 IRE test pattern, “full on”) and then a solid black screen (0 IRE test pattern, “full off”) for calculating the ratio. The ratio of these two brightness values is called the dynamic or full on/off contrast ratio.
ANSI or Static Contrast Ratio – ANSI or static contrast ratio values are valid and hard to manipulate measurements. Their calculation process involves projecting only a single image. The picture consists of 16 rectangles, eight black and eight white, arranged in a checkerboard pattern. The contrast ratio is calculated by averaging the brightness value of all eight white squares followed by averaging the value of the eight black squares. The ratio of the two averages gives the ANSI or static contrast ratio.
ANSI contrast ratio is a more accurate value as compared to full on/off contrast ratio. It is because the light emitted by a projector’s light source will scatter inside its lens assembly. If a projector is displaying the fully black test pattern used for the full on/off contrast ratio test, there is no scattering of light as the brightness is almost zero. In comparison, when the checkerboard pattern is used, half of the image is white. The projector has to emit a lot of light to display the image. It will bounce and scatter inside the light engine and lens assembly and will compromise the black areas of the image. It can significantly reduce the black luminosity levels of the picture by anywhere from 2x to 20x or even more. The ANSI contrast ratio of a projector will be significantly lower than the full on/off contrast ratio.
In the real world, the imagery will contain both black and white light. Therefore, ANSI contrast ratio measurement is close to the real-world scenario and the better method.
Dynamic Contrast Ratio – Some manufacturers list a dynamic contrast ratio for their projection devices. It can be considered as a type of full on/off rating and calculated in the same way. Many modern projectors use various technologies to control the light emitted in real-time. The devices can change the brightness emitted by adjusting the lamp power or blocking the light physically using a shutter. These adjustments are made according to the brightness levels of the imagery. Lowering the brightness allows the projector to display even darker black levels in the imagery as compared to standard projection. The contrast ratio calculated is listed as dynamic contrast ratio instead of full on/off contrast ratio as the value is augmented by such technologies. While it is a great technology overall, it can significantly alter the contrast ratio of the projector.
Dynamic contrast ratio values are the highest, followed by full on/off contrast ratio readings. ANSI contrast ratio values are significantly lower than either of the two. A device may have a dynamic contrast ratio value of 200,000:1, a full on/off contrast ratio value of 50,000:1, and an ANSI contrast ratio value of 1,000:1.
Contrast Ratio and Image Quality
The contrast ratio of projectors alone does not decide the image quality. While it denotes the blackest black and the whitest white a projector can produce, it does not represent how the projector will display all the shades lying between the two extremes. Checking the gray color reproduction capability is equally important. The imagery will appear pixilated if it contains shades of grey that the device can’t display. It may impact image quality and the viewing experience of users.
Also, the contrast ratio ratings of two different projectors are not directly comparable. A projector with a 4,000:1 contrast rating won’t be two times better than a projector having a 2,000:1 contrast rating. Still, comparing the ANSI or static contrast ratio can give users a fair idea of how devices will perform. A projector with a 1,000:1 static contrast ratio is ideal for home theater setups. It will present a well-detailed picture in dark scenes, and different shades of white will also be easily distinguishable.
Users who already have a projector with a low contrast ratio can take a few steps to enhance image quality. Controlling the ambient light can assist in improving the perceived contrast ratio of projectors. A small amount of light can reduce the contrast ratio of a projector significantly. Viewers should close uncovered windows to block natural light and turn off artificial bulbs and lights wherever possible. Using a projector screen with a darker material will improve the contrast ratio of the imagery as well.