I have never used a bear spray, so I read this thread from Canadian Canoe Routes with interest.

Several members of the group decided to discharge their bear sprays as a small 'research project' since all the canisters were at least three years old and didn't have expiration dates.

"From what I've seen they all seem to start as a stream and over the course of about 10 to 20 feet move out into a cone around 6 foot diameter. The one thing that surprised me was the big difference in how fast they opened up into a mist, how far the stream went and how long the spray lasted... We all liked and settled on the make the got the furthest distance before coning... I'm guessing 25 plus feet and a 6 foot cone at that distance. We got just over 7 seconds of pepper."

He said the brand they all decided to buy was Counter Assault for duration and distance, and it has a glow-in-the-dark safety. (This link was from 2007) Bear spray

So, if the spray comes out initially as a stream, you could probably shoot it straight into the eyes/nose of a bear that was actually in the process of attacking someone else (or yourself), since it doesn't come out initially as a mist.

If the bear had the victim's head in it's mouth, the spray would probably still affect the victim, but if the bear had hold of an arm or leg or torso, the person holding the canister might be more likely to use it if they knew the spray didn't come right out in a cloud that would instantly affect everyone in the immediate area.

Sue