Gesture Drawings vs. Thumbnails
A gesture drawing is essentially a fast, observational sketch where the artist is looking, interpreting, and drawing what he sees before him. Speed drawing is another term for these, if you like-although the drawings still have to be accurate even if they are drawn quickly. Gesture drawings for animation purposes can even be an exaggeration of what is seen-as long as these exaggerations (or caricatures) are accurately reflective of what is seen and not just bad drawings. A gesture drawing is wholly concerned with the observer looking analytically at the pose or position of a character (or object) in front of him and then drawing speedily
In other parts of the book, you will be asked to create quick, imaginary, small-sized concept sketches of things you need to conceive or think up. These are called thumbnail drawings. Thumbnail drawings (also known as thumbs or thumbnails) are effectively a very quick scribble, sketch, or doodle that gets an initial idea down on paper ahead of further study or research taking place. These are therefore not final sketches, or even observational gesture drawings in any way. They are more a stream of consciousness kind of thing, where you brainstorm your thoughts and get them down as quickly as possible. They are effectively the foundational basis upon which all future work is based, which is why many animators “thumb out” their animation ideas before fully commiting them to paper or computer.