Optical Performance Metrics

Contrast Ratio

The contrast ratio is the ratio of the luminance between a pixel in the “light” state compared to the same pixel in the “dark” sate. Typical contrast ratios for the different technologies are:

• TN 9:1
• STN 10:1
• FSTN 15:1
• CSTN 25:1
• TFT 300:1

Brightness

Brightness or luminance of a display is the measure of light output from the LCD panel. It is typically measured in “Candelas per square meter”, or “nit”.

Response Time

The response time of a liquid crystal cell is defined as the amount of time required for the LC fluid to switch from 90% of a given a pixel state to 90% of the opposite state, for a given temperature. This is also be considered, the amount of time required to change the entire image on the LCD panel. Therefore, the inverse of the response time will give the frames per second capability. Typical response times for the given technologies are:

• TN 200ms
• STN/FSTN 350ms
• High Speed FSTN/CSTN 80ms
• TFT 35ms