HOTUS TECHNOLOGY - What is the contrast ratio of smart projectors?

　　Contrast ratio is one of the main specifications to look for in a smart projector. Many buyers make purchases based on the brightness levels and contrast ratios of different devices. Equally confusing, however, is that projectors have contrast values ranging from 100:1 to 500,000:1. Understanding the various methods used to calculate contrast values and understanding how contrast affects image quality can help buyers choose a better projector from the available options.

　　What is the contrast ratio of a projector?

　　Contrast ratio defines the ratio of the whitest shade of white to the darkest shade of black that the projector can display. Simply put, if a projector has a contrast ratio of 2000:1, it means that the whitest shade it can display is 2,000 times brighter than the blackest shade it can project. A higher contrast ratio means the projector can project darker blacks and brighter whites. It will make the picture more detailed and improve its clarity and quality.

　　Static Contrast: ANSI or static contrast values are valid and difficult to manipulate measurements. Their computational process only involves projecting a single image. Divide the picture into 16 rectangles, 8 black and 8 white, arranged in a checkerboard. Contrast is calculated by averaging the luminance values of all eight white squares and then averaging the values of the eight black squares. The ratio of the two averages gives the ANSI or static contrast ratio.

　　ANSI contrast is a more accurate value. This is because the light from the projector's light source is scattered within its lens assembly. When using a checkerboard pattern, half of the image is white. A projector must emit a lot of light to display an image. It bounces and scatters within the light engine and lens assembly and affects the black areas of the image. It can significantly reduce the black level of a picture by a factor of 2 to 20 or more. The projector's ANSI contrast ratio will be significantly lower than the full on/off contrast ratio. In the real world, the image will contain black and white light. Therefore, the ANSI contrast measurement is closer to the real scene and is a better method.

　　Dynamic Contrast: Some manufacturers list Dynamic Contrast for their projection equipment. Many modern smart projectors use various technologies to control the light emitted in real time. These devices can vary the brightness emitted by adjusting the lamp power or physically blocking the light with a shutter. These adjustments are made based on the brightness level of the image. Lowering the brightness allows the projector to display darker black levels in the image compared to standard projection. The calculated contrast is listed as dynamic contrast, not full on/off contrast, as these techniques increase the value. While it's a great piece of technology overall, it can dramatically change a projector's contrast.

　　The dynamic contrast value is the highest, followed by the full on/off contrast reading. ANSI contrast values are significantly lower than either. A device may have a dynamic contrast value of 200,000:1, a full on/off contrast value of 50,000:1, and an ANSI contrast value of 1,000:1.

　　What is the relationship between contrast and image quality?

　　Projector contrast alone does not determine image quality. While it says the projector can produce the blackest blacks and the whitest whites, it doesn't represent how the projector will display all the shades that lie between the two extremes. It is equally important to check the gray reproducibility. If the image contains shades of gray that the device cannot display, the image will appear pixelated. It may affect the image quality and user's viewing experience.

　　Also, the contrast levels of two different projectors cannot be directly compared. A projector with a 4,000:1 contrast level is not twice as good as a projector with a 2,000:1 contrast level. Nonetheless, comparing ANSI or static contrast can give the user a rough idea of the device's performance. A projector with a static contrast ratio of 1,000:1 is ideal for a home theater setup. It will render detailed images in dark scenes, and shades of white will be easily distinguishable.

　　Users who already own a low-contrast home projector can take a few steps to improve image quality. Controlling ambient light helps improve the projector's perceived contrast. A small amount of light can significantly reduce a projector's contrast. Close uncovered windows to block natural light, and turn off artificial bulbs and lights whenever possible. Using a projector screen with darker materials will also improve the contrast of the image.