I've got a couple of years experience doing concept work for a feature animation. The Studio is small and the concept team is smaller. There are only 4 of us full timers to handle concept art for the big feature animation project and the various smaller projects that they get so often. We have a few interns and later on a few more full timers to help us out. One thing I found was the more adaptable you are, the better you'll do.
Concept art ranges from coming up with ideas, putting those ideas into comprehendable layout designs and eventually you're going to write notes about it to ensure the 3D or production people know how to make things work. Concept artists also do storyboards, color keys, and when the conceptualizing period is over for the project, you have to move into production and continue the project....unless your studio has a constant stream of fresh projects coming in that will require your services all the time (like Pixar).....otherwise, expect to move into production. Whether its texture or background painting or even low poly props modelling, maybe filling in as a motion capture actor or even move into scheduling and paperwork when the production phase starts, or even doing editing or motion graphics in post production.
I think a concept artist is an all rounder, good in everything, not exceptional but good enough to get by. But because he's good in everything, he does everything. Its not an easy job.
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