The main difference of course film compositing as image-based animation do not care about size of results, but Flash design cares, which mostly have to transmit through Internet but still keep a reasonable framerate. Visitors couldn’t suffer from long time loading, also, small screen or low quality of .flv, .rm, .avi movies are limited to be used in very few situation, as well as a back-end media server necessary.

What I’m talking about here is differences technically. Flash is another kind of movie, another kind of film, it could still have better quality in wide screen if smart organized. Flash can put layers, use media assets repeatedly, as well as coding effects with actionscript. But know first differences is necessary before think about what can we do in Flash design with film effects.

1. Flash have to use less size of media assets, and maybe change something-not-so-important to still image. We know even in film compositing, we could always use still images, while the results could be ‘animated’. But if in the scene of film some parts is not important to eyes, we can use still image in Flash instead especially if it’s too large like a background, we change position, rotate, resize, blur(moving further distance) and ignore small changes of those.
2. Film could use varies of effect plugins, Flash couldn’t, Flash use have to coding with actionscript, even when those plugins we can code (always but not all), we have to think about the CPU/Memory used at that time and frame.
3. Film could be very detailed while Flash design have to be neat. We should emphasize what important you want to show for eyes, make that detailed while simplify others. Because Flash also animated film, human’s eyes could only remember simple visual details, so in Flash we could benefit from this.