I've been asked a few times how I go about using reference. To my mind there are two kinds of reference: personal and sourced. Personal is the video an animator shoots for themselves, and sourced is video an animator will find on YouTube, BBC Motion Gallery, etc. The following thoughts apply to both and I will point out instances where they are different.
It's important to note that the finished, rendered product is what people will see, not any of the steps along the way. So reference, in my mind, should be a help and a guide, not something to be copied. Rotoscoping never looks very good.
Whenever I begin any shot, whether at work or at home, the first thing I do is thumbnail. I get down my raw, uninformed ideas in the form of simple posing. Then I film or try to find reference with these ideas in mind. The ideas might change once introduced to the light of reality and that's okay; the thumbnailing is just pre-planning.
In the process of looking at the various takes I've filmed, or the different video clips I've found, I may edit these different takes together to make a supercut. It's not so important to have a single continuous perfect video clip to use as reference; people are going to see your finished animation up on the screen, not your reference.
Once I have this supercut reference, I thumbnail again, but now it's informed by the video and it becomes about finding the key poses, amping them up and making them stronger, more readable and more entertaining. I'll draw key poses, breakdowns, and make notes about little details I've seen in the reference if I can't reflect it in the thumbnail.
It's at this point that I ignore the reference for a while; I have enough information to start blocking. I may glance at it when I start splining, but I won't really look at it again until polish to make sure I'm not missing out on anything, to clarify my notes from earlier, and to make sure I haven't departed from the reference in a detrimental way. The animation needs to stand on its own and work within itself, and I think the only way to truly do that is to give it room to breathe and become its own thing.
That being said, I thinks it's fine to go back to the reference if something isn't working. Maybe a weight shift isn't feeling right, or a blink is just wrong. The reference will show you what the reality of that movement is. If it isn't in your reference, shoot more or find more; you need good foundations for any animation you do.
Gather reference, rely on it, but don't let it hold you back from making your animation amazing.
Keep on keyframing!
