It's important to note that blinking in real life ISN'T AT ALL the way actors/animators use blinks. Ed Hooks should chime in here, but we blink in real life because of need. Actors blink for dramatic (or comedic) impact. IOW, your characters shouldn't blink unless it helps convey the action at hand.Now with that in mind, it's purely up to the animator, director, and current storypoint to use synchronous or asynchronous blinks. I have to laugh when I read messages from folks looking for or asking for "rules" when it comes to things like this.To me, the rules are simple: the character does whatever is in character for him/her/it, whatever fits the style of the animation, and whatever conveys the mood, action, or point. No?

Mike Caputo.

I read some interesting theory of blinking in the book on film editing entitled "In The Blink Of An Eye". I believe the main idea there was like following: We blink for a reason we need eye to be wet. How often we need to blink - depends for the most part on how quick eye gets dry, and this in turn depends on many things, like air humidity, wind speed, personal psycological condition, etc. The exact moment we blink is being shosen unconscious, but so as to not interrupt the perception of valuable visual information. That is after we looked in one direction for a while and get "enough" information from that, we blink and change focus of interest. By analogy, sometimes we blink to separate one thought from another in a thought process.

Avenir Sniatkov.

I agree there are no rules, but some good places for blinks are:

1. When a thought process is finished or a decision is made - I once
heard a film editor say that he likes to cut on blinks because blinks
signal completion of whatever is going on in a character's mind

2. in the middle of a head turn

3. whenever there is a quick eye movement - try looking up quickly
without blinking, it's really hard.

Timing: experiment. The eyelids can go from open to closed in as little
as one frame. The faster they come up, the more alert the character looks.

On Pixar's eyeblinks: Pixar animators offset the eyes by a frame or so,
I guess to make the blink look less mechanical? It's a pretty
distinctive style, and sometimes makes the blinks more noticeable. But
it's also kind of endearing.

Marion Gothier.

one place I like to use blinks is as part of the anticipation of a head turn, for example just before a character turns it's head to look in another direction or shifts focus on something. another place I like to use a blink occasionally is when lip syncing the "P" sound, I don't know why but if I'm lip-syncing and feel that my character needs a blink just to add some life I'll place one there. For some reason I notice myself blinking or the sensation of blinking on that particular phoneme when I watch myself in the mirror running through the dialogue. Try saying the "peter piper thing" and you'll see what I mean.

John Siciliano

In addition to all the great comments, I thought I'd throw in my two cents. . .For me, I put in a blink (usually) when:

1) the acting or emotion of the scene calls for it. (nervous? shy? sad? More blinks. Angry? Interested? Curious? bored? less blinks.)

2) Like people have said, to allow your brain to process fast moving visuals, we blink. So blinks on fast head turns, or changes in focus are good. If you are listening to one person and then another, you will most likely blink somewhere between that change of attention.

3) This is what I thought was interesting. Someone here told me about a book (sorry - can't remember the title right now) where a film editor discussed how he edits his movies. Basically, he makes the cut where an actor blinks or when
the viewer naturally "feels" like it's time to blink. His whole theory is that our brain is viewing a film whenever we are awake and that our eyes are the editors, and the blinks are our eyes "cutting" the "scenes." This is why we blink when our though process changes or eye direction changes, and so on. That's his theory, anyway.

As for ideas on how to animate a blink, this is something that I've used a lot which I learned from another animator here - I offset the blinks but the actual closure of the eyes occurs on the same frame. This allows for the organic offset without the cartoony (but cool, of course!) eyeblinks that Pixar, for example, often uses.

Basically it works like this:

Frame 10: both eyes are open
Frame 11: Left eye begins to close
Frame 12: Right eye begins to close
Frame 13: BOTH eyes are completely closed
Frame 15: Left eye completely open
Frame 16: Right eye completely open

Anyway - obviously there's not hard and fast rule on how to do these things, but this is something that has worked well for me and seems to look pretty natural. You'll also notice that in the frame counts I threw in there is a slight fast-in and a slow-out, which is pretty normal for a blink. If you switch that, and slow into a blink and speed out of it, you'll get the look of someone who is tired and trying to stay awake. If you slow in AND out, you'll get someone who is either a tough badass or is bored or is falling asleep. Fast ins and outs look a bit frantic to me.

Shawn Kelly.

Not much I can add to what's been said...which is awesome stuff by the way. I feel that eyes is one of the most important things in any character right after the body language. Blinks....I think the part in "Illusion of Life" where they talk about
eyes/blinks/eyelids, etc....is pure gold man. Some really amazing information about eyes/eyelids in there. Some of the things they mention in it about blinks:

"In blinks there should be a feeling of flesh and thickness to the eyelids. Where there is only one inbetween, slow out of each extreme. Inbetweens on a blink should animate smoothly and not change angle or wobble. Blinks of disbelief, puzzlement or wonder usually are shown with a slight squint. Blinks area useful device to ease the shock of going into a held drawing. The simple addition of a blink during a hold recaptures the living quality. "

Other stuff I try to do is to actually anticipate eyeblinks over a frame or two. Not that is very noticeable, but when you have closeups I really think it makes a difference. When we dart our eyes, the pupil eases out...I also noticed that with blinks. The eyelid doesn't close in a constant way, we have slows in and out of the open/close move....and sometimes I noticed we hold the blink for more than one frame. Depending on the emotional state of the character you can also play with the timing on the eyelids when blinking. It's not the same thing to have a character closing his eyelids over three frames, that over ten frames. It tells you a lot about how this character is feeling at the time...or about the personality of this character. Also, the number of times we blink repeadtely can add to another emotional state of the character....I think. Not too sure if what I just wrote made sense. But for example, I remember this one scene in "The Green Mile" where Tom Hanks and David Morse are talking to Michael Jeter in his cell. There is a moment in there where Tom Hanks is blinking like a maniac due to the thought process of what they are talking about that I think is really good to study. Some actors are really really good to study regarding eyes. Jack Lemmon is such a good reference to study eyes, specially in films like "Glenngarry Glen Ross" or "The apartment".

Carlos Baena.

Blinking. A human blinks once every four seconds. This timing can change according to what emotional state the character is in. If anger is your dominant attribute then the blink rate should decrease to once every six seconds. The reason behind this is physical; the eyes open wide in anger, achieving a glare. If you are acting nervous then the blink rate increases to once every two seconds. This reaction is involuntary. Blinking brings realism to your characters but also emphasizes a particular emotion or mood.

Unknown source.

When we blink unconciously, it's because our eyes are dry. But the rate at which we blink depends on our state of mind. The more conciously/intently we are "looking" at something, the less likely we are to blink. So the sniper watching his enemy and the girl actively daydreaming about her fairy kingdom will blink much less often than the guy sitting in the middle of a boring office meeting, and the geeky boy playing his favorite video game won't blink at all. So even these unconcious blinks are dependent on the personality/situation of your character. As a rule of thumb I'd say your average person just sitting there will blink once every couple of seconds, but I'd also say an animated character blinking that often would look rather odd. I'd say that unless your character is very photoreal, the best way to use an unconcious blink is when the character isn't actively doing much of anything, as it adds a bit of life to him, but even there only put in one or two blinks. Anyways, hope that helped :)

Ted Young

I usually blink into and our of each action and on eye direction changes. It's a good idea not to let too much time go by without a blink (3-4 seconds) or your character will take on an odd look. You can also mix in 1/2 blinks and blinks in pairs to give a more informal look. I heard somewhere that politicians are coached to blink a certain number of times per minute (can't remember the exact number) as too few make them look dazed (Steve Forbes) and too many will make them look nervious and unsure of themselves. See ya,

Chris Bailey

I like to avoid making the right blink precisely identical to the left blink. I'm talking about tiny, almost-imperceptible differences that help me avoid perfect symmetry, and thus help the blink to appear more natural rather than robotic. For example, the in-between (halfway between closed and open) could be slightly higher in the left eye than it is for the right.

Tim Hatcher.