The Ascension Project
Armor Proficiency (Light)
Benefit: When a character wears a type of armor with which he or she is proficient, the character gets to add the armor’s equipment bonus to his or her Defense. Also, the armor check penalty applies only to Acrobatics, Climb, Escape Artist, and Stealth checks.
Normal: A character who wears armor with which he or she is not proficient adds only the armor’s nonproficient equipment bonus to his or her Defense. Also, he or she suffers its armor check penalty on attack rolls and on all skill checks that involve moving.