What do lumen and contrast mean in the parameters of mini projector?

Lumen: the unit of brightness, which determines the size of the projection area. The higher the brightness, the larger the screen that can be projected, and the more applicable occasions. The so-called lumen is the physical unit that describes the luminous flux, which is interpreted as a candle in physics.

. Contrast is a measure of the different brightness levels between the brightest white and the darkest black in an image. The larger the difference range, the greater the contrast. The smaller the difference range, the smaller the contrast. The good contrast ratio of 120: 1 can easily display vivid and rich colors. When the contrast ratio is as high as 300: 1, all levels of colors can be supported. However, contrast and brightness face the same dilemma. At present, there is no effective and fair standard to measure contrast, so the best way to identify it depends on the eyes of users. Contrast: color layering, the higher the contrast, the stronger the color layering and the more realistic it is.