Best of all, Johnson's work shows animals who are entirely free to come and go - though being in the right place to take their photos requires lots of patience.
"The birds have to be comfortable with you. I basically sit by their favorite flowers, sometimes waiting 30 minutes for them to come," she said. "Then I would take a shot, and they'd leave for another 30 minutes. To them, I don't even exist."
Check out more of Johnson's hummingbird portraits below.