I just disenchanted an item with +50% magicka regen and +12% destruction spells but only ended up learning an enchantment with +10% magicka regen and +5% destruction. The same thing happened for similar items: the enchantment I gained was significantly diminished. How do I get closer to what I had before? Do I have to disenchant more of the same item?
When you disenchant something, you're not getting a percentage of the enchantment you learned. What you're getting the ability to use that enchantment: in essence, the base enchantment upon which you built better ones.
So it doesn't matter what your skill is when you disenchant an item or how big of a bonus the enchantment on that item has: you'll always wind up with the same base enchantment to start off with.
Instead, what matters is the size of the soul you use, any perks you have, and your enchanting skill when you go to enchant an item: larger souls and more enchanting skill results in better enchantments placed on items.
I just got level 100 enchanting last night and found that with this specific enchantment (+5% destruction, +10% magicka regen) it only scales up the FIRST skill and not the second. So I got 17% destruction cost but still +10% magicka regen. I think this is a game bug because there are two stats and is really game breaking for me at the moment.
I don't necessarily agree with Mark's answer that you "always wind up with the same base enchantment to start off with".
For example, I disenchanted a ring of smithing that gave an 8% bonus, and now 8% is always the starting point whenever I want to enchant a new smithing item. At the same time, I disenchanted an item that gave a 12% sneak bonus, and so 12% is always my base for sneak enchanting.
This means that with my curent Enchanting level of 74, and with 3/5 enchantment perks, my smithing enchanting maxes out at 15% bonus, while sneak maxes out at 20% (using a black soul gem, filled grand for both).
So, to me it seems like the higher your enchanting level is when you learn an enchantment (and perhaps a higher percentage bonus on the item you are learning from) will net a higher base percentage for that particular skill.
In line with Bilge's initial question, the game won't let you "re-learn" a skill. So, by my example, if you learn a skill at a low percentage early in the game when your level/perks are low, you will be stuck with that percentage as a baseline for the rest of the game. Again, even if you find an item with a higher bonus percentage, the game won't let you disenchant the same skill twice...so you're SOL at that point.
This is how the game is working for me. Anyone else seeing similar? Perhaps this is a result of the latest patch? I'm playing on a 360.