Radius in such situations is almost never an issue.
The crippler is the size of the conduit.
Typical minimum for trivial need: 3/4"
Robust data-com spec out 1 1/4" drops -- for which j-boxes are in mass production (yet special order from your distributor -- such big KOs have to be spec'd) (4-11s)
It's not uncommon for the drops to have no elbow at all. Instead, the drop is a sleeve capped by a plastic bushing -- typically a white nylon style -- Arlington pitches theirs all the time in EC Magazine.
It's common for the spec's to call out for bushed entries, BTW. Bare pipe won't do.
Eriksen sells a bender that kicks out mild sweeps in EMT.
It's popular in the data-com world, too.http://www.ericksenbender.net/
This is usually a company tool. Its sweeps are so gentle that it's possible to go to down a size for data-com sweeps. (ie, 1" replaces 1 1/4") If you do this often enough, then the bender pays for itself.
[ Note: downsizing data-com drops is only possible if you've got the data-com contract. In all other cases, you're in the blind -- and will have to follow the contract spec's. These are usually worked up on the most conservative (oversized) basis so that the writer doesn't get bit by final results.]
In all cases, never attempt to get away with 1/2" EMT.