In one of his instructive books on comics--sadly, I forget which--Scott McCloud shows different ways that artists have developed to show a character moving fast. Naturally, the artists behind Flash were especially creative in this area. It's one way that comics-style illustrations, unlike drawings in other genres, show the invisible.
Among the choices are:
- motion lines, of two sorts: either paralleling the outline of the moving character or parallel to the direction of movement. The latter has led to some drawings showing a crackling path left behind by the character as he or she moves really, really fast.
- blurring the back of the character while keeping the front crisp and recognizable.
- multiple images of the same character in a single panel; sometimes all but one are "ghost images" to indicate where the character just was.
- keeping the character in focus, but blurring the background as if it's zooming by--a technique favored in Japan.
I noticed last week that Photoshop and similar programs have made yet another technique available to artists. It appears in this detail from art by Alé Garza from Ninja Boy: Faded Dreams, published in 2003.
It looks like Garza and his colleagues first drew the character Nakio and his little target crisply, with motion lines, on one layer of a Photoshop image. Then they blurred Nakio's fast-moving fist and foot, and much of the little creature he's punching (I don't remember why), to replicate the effect of fast movement in a photograph.
The sound effects of "KRAK" and "POOM" were apparently created as a separate layer in the image, and thus remain crisp. (They're another example of comics showing the invisible.) The background may also be its own layer.
At the upper left you can also see how blurring and/or layering creates the illusion of hazy sunlight on this gentle scene.
I'd welcome better insight from anyone who's used this technique or others like it.