So I have an old Sigma 28-80mm standard AF lense.. I cannot for the life of me find this specific lense anywhere on any site. I have scoured the internet. I keep seeing the 24-70mm but not this one... I am about to purchase a D5100 (YAYYY, FINALLY!) and need to know if the lenses I have are compatible. IS THIS ONE JUST NOT COMPATIBLE WITH THE D5100??!! I'm dying to know. I can't find a yes or a no anywhere and really need to know before I purchase. Any info would be soooo appreciated! Thanks in advance to anybody that can help me!