The 1.4 will up the focal length to 540mm. I already have the 2x, but AF doesn't work with it on the 30D. You need the 1D or 5D to keep AF with that one. Something about going over f/8. The 30D loses it with those lenses and the 2x, while the 1 and 5 series cameras keep it. The 1.4x will up the f/5.6 400l to 8 and it's supposed to keep the autofocus. It's a bag of worms though. Some work some don't.