The verdict
One package stands out because of its wealth of features, stability and prospects. And that package is Blender, which can be used to create simple animations right through to advanced physics effects.
Within one program are all the tools you can imagine. Indeed, you won’t even know they’re there until you search for them.
The Blender foundation even has a yearly conference covering all aspects of animation with the program. This makes Blender the strongest contender; however, when choosing a program you may want style over features. It’s also important to remember that this is a 3D package and the characters aren’t drawn, but instead created using cubes and spheres that are changed into your preferred shape.
Sometimes a simple interface that mimics drawing on paper is preferable. Both Synfig and Tupi closely mimick drawing on paper, which makes it comfortable when making the move from paper to the digital canvas.
Synfig also enables you to sketch in bitmap fields, and through the use of Bézier curves. Such a workflow can actually enhance your current habits from paper rather than forcing a complete change in drawing technique.
Keyframes make it easy to draw a few frames and let the software fill in anything that’s in between. However, this technique may lead to stale and mechanical movement so be prepared to fine-tune details − especially in facial expressions − before you publish.
When you’re using an “onion” view, you can use pre-made drawings and trace around it and then create new frames by changing the existing picture. This works particularly well in Tupi if you start with one picture for each object in your scene. You can then quickly fill your scene, ultimately creating an animation.
With GIMP you can use simple contour drawings and colour them using the many features and layer techniques to add colour and different effects. There are effects for making your drawings look like other materials, such as wood or metal, too.
“Sometimes a simple interface that mimics drawing on paper is preferable…”