I got a couple great questions regarding eyes from Christopher and Avner.
Christopher asks: Can you share more on the subject of eye darts and your technique to approaching them in relation to the social triangle and eye blinks? And Avner wrote in to ask: How do you animate eyes and eyebrows on giant characters like the ones in Transformers?
Those are both great questions and obviously related. As we all know, your eye animation is probably the most important single aspect of your acting performance outside of the general body language. People generally see the body first, then the eyes, then everything else, so you always want to first sell the emotion in the body, and then really hammer it home with the eyes.
"Eye animation" could include general eye shapes (emotional shapes), eye darts, pupil animation, blinks, and sometimes you might lump eyebrow animation into this category as well. All of these things work together to communicate emotion, thought process, and even unspoken lines of dialogue!
The main thing to keep in mind with eye darts, particularly in regard to blinks, is that you should not think of them as random movements that you throw into your scenes willy-nilly. You can use your eye darts strategically to show a shift in thought process or even to help sell an emotion (such as one person's eyes darting back and forth between the eyes of the person they talking to, searching for the truth).
Other general eye-dart tips:
1. They're fast! The eyes can really move quickly. Study your friends eyes and you'll see a lot of micro-movements as well as larger re-focusing movements. All of these movements will happen very quickly. Generally you're talking about one to two frames, in most cases, unless you're slowing it down for a specific reason.
2. Generally, eye darts are very quick and somewhat linear in motion. You could ease out of the first pose a bit, but you should hit that second pose really hard, almost robotically.
3. Plan your eye darts and use them wisely! Too many eye darts will feel spastic, freaked out, or electrocuted. No eye darts can very quickly feel dead (like doll eyes), but can also be used for effect (drugged, etc).
4. You need to give the eyes time to focus as well. Don't just have the eyes darting all over the place if the idea is that they are really focused on something. If they are focused, then only use VERY subtle eye darts that will help the character feel alive.
5. The further away something is, the less the eyes will dart when they are studying it.
6. If a character is tracking a moving object (such as a car), it's usually good to break up the eye movement with some darting movements that focus for a couple frames before moving on. With a slow-moving object, you can get away with a smoother eye-tracking motion, but as soon as the object has some speed, this will feel robotic and weird.
In regards to tying eye darts in with blinks, obviously the goal should be one cohesive eye performance, so you should really study what your eyes did in your video reference and see how that feels - and more importantly - figure out WHY it feels that way. Smaller darts won't necessarily have any correlating lid movements, but larger darts might, and the largest might want to have a blink happen as the eye shifts focus so far. People will almost always blink on a fast head turn, and the same generally holds true for large eye-shifts, but not always. I'll talk more about blinks next time, this is getting crazy long! :)
As far as animating the eyes of a character that doesn't have flesh and skin (robots, etc), you really should strive to recreate as identifiable performance as possible, no matter what. The design of the character can never be an excuse for you. Sure, some designs will work better than others, but no matter what character you are given, try to find ways to use that character's design to create shapes, movements, and ideas that the audience will recognize and identify with.
For something like Transformers, a huge goal for us is to strategically animate pieces on the face that will best communicate and "read" to the audience, so if you are working with a robot, my advice would be to look for pieces that can work as brows, lids, pupils, iris, etc.