...and I was correct! It was quick and easy, and I am really happy with the result.
Canon 7D, Canon 400mm f5.6L, ISO 100, f5.6, 1/125s
Converted in LR, further PP in Pshop
edit- I should add that I used mirror lockup, and a wireless shutter release, and had the gear firmly set up on a sturdy tripod/head. (The lens collar foot is clamped into the ballhead)