Refresh rate means how many times contents to be delivered completely every minute. LED display with low refresh rate will give audience trembling feelings. When photographed under digital camera, scanning lines will appear. Normally, refresh rate over 300Hz is the basic demand of human eyes. But for digital camera, scanning lines will disappear over 600Hz refresh rate. High refresh rate can promote the brightness and contrast ratio of LED display. Use digital camera can check whether there is snowflake and scanning line is a good way to measure.
Contrast ratio means the measure between the brightest white and the darkest black. Contract ratio is an important element of viewing effect. Normally the larger contrast ratio will leads to clearer and vivid color and images delivery. And with small contrast ratio, the whole display will looks grey. To adopt whole black SMD is the most efficient way to enhance the refresh ratio.