Hello\n\nI have a Canon 20D digital camera with the EF-S 18-55 lens and the Canon\n75-300mm f/4.0-5.6 IS USM EF lens.\nI have two questions.\n1. Where can I buy diopter lenses. I've found them on the internet (B&H),\nbut nothing for this camera?\n2. I would like to get a teleconverter. I'm especially interested in a Kenko\nTeleplus Pro 300 3.0X lens.. I would appreciate hearing from anyone who has\nused this 3X Tele Extender with the 300mm zoom lens that I described above?\nThank you.