Before filling the timeline with a flurry of frames, it’s helpful to draw key poses to mark the important moments. The starting key pose shows where the action begins. The middle key poses show the peak of the action, or where the body moves in anticipation of what’s to come. And the ending key pose(s) show where the action ends and completes.
Once you have drawn some key poses, ask yourself these questions: Can you understand the silhouette of the pose? Can you clearly see how this pose is visually different from the next key pose? If you answered yes to these questions, it means there is enough information contained within each key pose.
An interesting exercise you could try is to draw just three or four poses, or key frames to animate an action and then hit play. You’ll need to add temporary holds onto each of the key poses. Choose a simple movement like a character picking up a ball. Or pushing a box. Or jumping. And then animate the action using just three or four poses. When you’re done, see if you can clearly understand the action using only these poses. And if you can, chances are the key poses have enough information to tell a story.
Now imagine you added frames to all of these poses before you figured out the body mechanics. You’ll find it harder to adjust for anticipation or make big changes to the body’s angle, position of hands and so on. All of these adjustments have a greater impact on clarity in poses than polishing the drawings.
Once the key poses are clear, breakdowns are poses that can help clarify the direction of the movement, body mechanics, and so on between two key poses that confuse you. Once the key poses are clear, then in-betweens can help smooth the movement.
Think of the order in which these steps happen like building with bigger, simpler pieces before adding all of the fine detail. In-betweens are where you decide the spacing, which smooths out movement.
When you establish clear key poses, this will make onion skinning more effective for you because the drawings you’re skinning on top of will be more purposeful.