Blog Entries

How to make this film – Part 3

6mb source file .zip

Optimising GIF Anims

Gif anims work with delta compression, that is to say, differences between frames. Video footage does not optimise well because of the noise which changes from frame to frame (brighter lighting will alleviate this problem, but not solve it)

For example, in this shot you can see the noise moving:

gifgrain

Because the gif compression sees the video noise moving it saves every frame, even though we know better. To counteract this you need to set up some rough masks that follow the action, leaving a static version of the background with no animated noise to make the gif compression work. This can be done in After Effects in the same way as the other masks, and as they are not visible it can be done very roughly. Alternatively it can be done in ImageReady by using the layers

Other big savings in memory come from:

  • Lower resolutions
  • Fewer frames
  • Fewer colours
  • No dithering

I usually try to keep my gifs to under 10 seconds, and use about 32 colours, noise or diffusion dithering and a resolution of 160 x 120

ir

I use a frame rate of 12.5fps (half PAL frame rate, i.e. discarding every other frame) or 15fps (from a digital camera or half NTSC frame rate). In Imageready, set the frame delay to 0.08 for 12.5fps and 0.06 for 15fps. If necessary, add longer pauses to slow the animation down and make sure the audience can take in the action

Dithering simulates more colours, but having a more colours in the palette is always preferable. Converting to black and white can save a lot of memory, as can adding scan lines. But make sure to alter the brightness of your animation accordingly, black scan lines will make the anim appear darker and white will make it lighter

headlossgifb&wgifscan

That’s it. But remember, this is just how I make my films. It’s not necessarily the best way of doing things but simply one that works for me. Experiment and play around with the scene I’ve given you to see how I’ve done it, then expand on the ideas and techniques to make your films uniquely yours

Good luck!

29 March, 2005