Anything less than the radius provided by the conduit bender is probably going to kink the tubing. If you're not too concerned with little dents you can cheat a little by working the tubing out away from the inner surface of the bender and free bending it. I've done this and I have been able to get a little tighter bend than the bender would normally allow.
There are other methods; packed sand, heat, and special materials to fill the pipe before bending but they are involved and not always successful. There are also tools made for bending tubing. They might give you a smaller radius but EMT (conduit) is thin wall stuff and will kink easily no matter the method.
Good luck.
Tom