A talented animator I've been mentoring sent me the following email:
I was just looking at the playblast you sent to me last weekend. I stepped through it frame by framed and noticed that it seems you keyed your blocking on 8's and 4's. It looks good and I am curious as to why you use that approach. When you have a moment, could you please talk about that a little?
In my response, I realized that this was a habbit of mine that I have been incorporating for years, and it had been a long time since I thought about why. When I typed up the email, I was forced to dig from the back of my brain (a place into which only the boldest dare to venture), and even to drag down my copy of IOL from the dusty top-shelf, and found that as I responded, I was preaching to myself. With that in mind, I decided to open this blog, to post to anyone who would like to listen in on my self-preaching in hopes that, along with you, I will learn things that I had either forgotten, or can now think of in a new way, having garnered much experience since the last time I cracked open Frank and Ollies legendary work.
Yes, I do tend to animate on fours (4, 8, 16, and so on). There are a few reasons for this. First of all, [the animation my friend is speaking of] was my rough blocking pass, on which I'm trying to get a basic idea for the timing. Had I felt the need, as often has been the case, I will bring it down to even a 3 or a 2, or a 6, or whatever feels accurate, but in the rough blocking, fours keep everything organized, and a frame or two from final timing is close enough. It is recommended in The Illusion of Life (IOL, 230) not to take it below "4 frames apiece and no more than 24." This keeps everything simple (an acronymn thrown around a lot in this industry is K.I.S.S.- Keep It Simple, Stupid) and allows you to see whether your poses are working, whether they're "strong enough, or too strong, and if the amount of time allowed for the scene is going to be right" (IOL, 230) . That is reason number one.
Reason number two is based on something talked about in The Illusion of Life, although I'm making a liar of myself, as I can't seem to find it anywhere in here. Should somebody know the page number, I'd be very appreciative if you could send it my way (It is entirely possible that this was actually from The Animator's Survival Kit by Richard Williams. [Frank and Ollie, or Richard, perhaps] mention that they tended to animate in such a way that it broke things down for their in-betweeners to much more managable segments. If, for example, I was to animate a ball bounce, and I started on frame 1, then I did the key poses, and handed it off to my assistant to take care of the 'tweening, but I keyed it at 4, then at 7, then at 10 (on threes), he's now got TWO drawings to make instead of three, which is not a good thing, because it makes it more difficult for him to decide where those poses go. Imagine taking a piece of paper and being told "Fold this into thirds or fourths, to make 3 or 4 equal-length rectangles." Given the option, chances are, you'd go with fourths. Why? Because it's easier to fold it in half, then in half again, than it is to estimate where one-third of the paper is. The animator (who has an assistant) has created the paper. The two ends of the paper represent the keyframes that he/she's set, and the assistant now has to break it down. If the animator set those keys at 1 and 4 (or 0 and 3, in our case), they've told their assistant "fold this in thirds," because they've only got 2 frames to figure out the 'tweening, or two "creases to make in the paper." On the other hand, if they set those keys at 1 and 5 [0 and 4], they've told their assistant "fold this in quarters." That gives the assistant 3 keys to play with. A central key on which to base their timing, and one on either end.
*EDIT* In reading this myself, I think I oversimplified something: When you are animating, your poses will not be directly at half-and-half. You will seldom have a shot where in between frame 0 and frame 5, 3 is exactly halfway. You must, of course, incorporate easing in and easing out, overlap, follow through, and a dozen other principles that will sell the shot. My "fold this paper" analogy is meant strictly to demonstrate how it's easier to break something up by having a frame that comes at halfway (time-wise).Now, obviously, in our case, we don't have an assistant, but the principle still holds true: if you break down your shot in such a way that you're allowing yourself to "fold this in quarters" down the road when it comes time for cleanup, you're making your own life (or the life of whoever might take over the shot) a whole lot easier. Si?