How do we determine and categorize roast level?

Terms such as “light roast,” “medium roast,” and “dark roast” are often used to describe the roast level of coffee.  The problem with these designations is that they are often used by specialty coffee roasters in arbitrary and subjective ways based upon the perceived color of the roasted coffee.  What one roaster considers a medium roast is considered a light roast by others, and what another roaster considers a dark roast is considered a medium roast by others, etc.  The problem is the failure to use a more objective standard for color measurement.  To remedy this, the Specialty Coffee Association of America (SCAA) has adopted the Agtron Gourmet Color Scale as the industry standard.  This scale was developed using an Agtron light reflectance spectrophotometer to provide a numerical color reading for coffee ranging from 100 to 0.  The lower the number the darker the roast.  Ketch Coffee Roasters uses a roast color analyzer manufactured by Roast Rite to determine the Agtron color reading of roasted coffee. 

958575655545352515
Extremely
Light Roast
Very
Light
LightMedium
Light
MediumMedium
Dark
DarkVery
Dark
Extremely
Dark Roast