Board Thread:Skyrim/@comment-117.216.29.63-20140415085533/@comment-9421524-20140415095025

All improvements with smithing are level dependent, but having the corresponding perk allows you to improve it twice as much. For instance, level 100 smithing but no perks, you could improve everything to Legendary, but if you then bought the perks for them, they could be improved again.

Lets say a weapon at Legendary with no perks does 50 damage. Buying the perks would then put the damage to 100, but it'd still just be Legendary.