Basically the question is how many frames is enough for simple things like walking, taking things, talk, ect. and when it is too much?
Personally speaking I try to have a "high-frame rate" which I try for at least twelve frames per second for slow animations (walking and grabbing things) and about five-eight (sometimes even four) frames for fast frames. Anything after that I just get kind of bog down, I could aim for sixteen some times but I get tired and distracted easily (hey, a duck).
On the other end I also believe that anything going over 30 fps is kind of a waste, and maybe a little insane and going over 60 is utterly out of one's mind.
That is all I really got to say, what's your opinion?
I do my walking animations in 6 frames, talking animations in more, around 15-20, depends on the character. I think going over 15 in walking can be already waste of time, but it really depends on the overall "quality" of the game, I mean - it would look weird if character walked in 6 frames in a 640 game, while it is OK in 320 one.
More frames doesn't mean that the animation automaticly looks more natural and smooth. The first Super Mario Bros. had a walk cycle of 2 frames... So 2 is enough.
Also the slower the animation the more frames you need to make it look natural.
I have a answers for you.
The human eye loses the ability to notice rude changes in a form (related to size, shape, color or position) with 25 frames per second. This means that, just in theory, every animation, regardless of its lenght of complexity must have 25 frames for each second it lasts. This is a pain in the ass when you're an amateur game developer, I know, but I have some good news.
The human brain can obviate some things. If you're looking an animation made with real photography, it will look strange if it has less than 25 or 24 fps, but if you're looking at an animation made with drawings, the brain loses the quality to notice the lack of frames. This and the ability of our brain to complete visual information makes it possible to make an animation of 12 frames per second something aceptable. In fact, traditional animation is made just with 12 fps, maybe some movies are made with 24 fps, but usually it's just 12 fps.
So, does any animation should have 12 frames per second it lasts? Again, yes in theory.
If we're talking of a videogame with high-res (640x640 or higher) Yes, as the sprites are bigger and movement is more recognizable. But in a low-res game (our beloved retro-traditional 320x240) you can use less frames per second. How many less frames? It depends on your skills, your patience, and of course the animation itself.
One hint. The human brain starts to recognize a correct walkcycle at 7 frames per second. Less frames makes it look weird.
End of the animation class, boys and girls. Now go home and remember to do your homework.
7 frames actually looks weird to most people visually. I prefer even frame numbers in animation, 6-8 is usually ideal for most adventure games (though I use 4 from time to time when I do c-64 art). Basically, the higher the resolution/larger the sprite, the more effort you should put into the animation to create something convincing.
You can usually cover the bases with just six or so. That's all that matters really, inbetweens are overrated.
I mean, just look at Bill Plympton (http://plymptoons.com)
Never really thought about this before.
I usually draw as many as I think it takes, test it, then add/subtract what's needed until it looks right and it smooth enough without being "glunky".
--Snake