Equipment Requirements

Many Weapons/Shields/Focus Items have a lvl requirement for a certain attribute. I have found that I can equip these items even if I don't fulfill the requirement. So body told me that you use, but you do less damage or get less armor or less energy. Is any of that true? If it is, how much less do you get?

This is true, until you fulfill the requirement, you won't gain the items full potential. How much you lose by not having the requirement? Not sure on that one but it is noticeable on weapons.