Armor: General information on the physical armor available in the game. The base cost for an Elemental Shield (0.95) is more than twice that of a plain Shield (0.45). For spellcasting, the difference between an Elemental Shield and a plain Shield effect can be more significant. For example, a transcendent Sigil Stone gives 20% Shield or 2 5% Elemental Shield.
When enchanting using Sigil Stones, Elemental Shield always gives you a stronger effect than regular Shield. When enchanting using an altar of enchanting, Shield and Elemental Shield strengths are very similar (Shield gives you at most 1 extra point). A 5% Shield spell only gives you the AR boost. For example, a 5% Fire Shield gives you 5% fire resistance and a +5 to your armor rating. When Enchanting, an Elemental Shield effect is often preferable to a plain Shield. However, the resulting armor rating is still only 85%, so the extra 15% Shield is providing no benefit. The Active Effects menu will confirm that the total Shield effect is 100%. Ciirta's Robes SI: 20%, together with 25 pts Fortify Health. Raiment of Arden-Sul SI: 25%, together with 11pts Intelligence and 11pts Willpower. It is possible to give your character 100% (or higher) Shield effect. This effect can be gained for spell making and enchanting via spells or choosing the Breton or Nord race. Shield effects only reduce base damage done to you. The Shield effect has no negative impact on the caster's Spell Effectiveness. Armor Rating is capped at 85% and cannot go higher. For example, you end up with an armor rating of 25 if you are wearing no armor and cast a 25% Shield spell, which is equivalent to wearing a full set of Leather Armor your total Armor Rating would be 50, or 50%, if you then put on a suit of Leather Armor in addition to the spell. Shield adds directly to the physical Armor Rating of the subject and is cumulative with worn armor.