A Perfect Mirror has 100% Specular Reflection and 0% Diffuse Reflection

Your Eye must be at an equal opposite angle to view Specular Reflection

In the Photo the image of the mountain on the water is an excellent example of specular reflection

Diffuse Reflection will scatter light in every Direction, like a wall that has been painted white.

This type of Reflection can cause the entire display to wash out and be difficult to read

Contrast Ratio in AMLCD displays as well as other display technologies is typically stated as a ratio of luminous intensity of a white (or a specific color) part of the screen to a black part of the screen.

A Contrast Ratio 5:1 is a typical minimum standard for text on a display to be legible.

AMLCD Display typically have a maximum Contrast Ratio of above 200:1 under optimal conditions.

Example

The white square in the black field measures 100FL
The Black measures .5FL
CR=(White – Black) / Black
The Contrast Ratio is 199 = ( 100 - .5 ) / .5

Note: Some Customers use CR = White / Black
Note: FL = Foot Lambert = Standard measure of the intensity of an emitted light.

HACR = (LWHITE + LR) / ( LBLACK + LR )

LR is dependant upon amount of reflection and how bright the ambient environment the display is used in is.

HACR is the measure that matters for a display that will be used in full sunlight or other bright environment. Many companies now are selling displays that are very bright, this is misguided, the goal is to increase contrast ration.