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:

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

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

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!

Import the footage into Adobe After Effects. The scene file above will only load into After Effects version 5.5 or above. The techniques mentioned below will work in earlier versions though

Set up the back plate shot behind the main action. Edit all the shots to get the timing right. You should end up with something like this:

We’re going to start on the shot called behind chair. It only needs a static mask. Create a mask by clicking on Rectangle Mask and dragging over the area you want to mask. Use the Selection Tool to move the mask points around and invert it so that it masks out my body. Increase Mask Feather to soften the boundary between the main action and the backplate

Repeat this for the other shots of me appearing

The next stage is to remove my head from the shot where I walk in. I made this easy by wearing a rather attractive green collar. That way all I need to do is key out the collar and create a garbage matte (a rough mask) to get rid of my head without having animate the mask frame by frame round my neck

Select the head less layer and choose Effect > Keying > Color Range. The Effect Controls window should pop up. This part is a little fiddly (especially because the footage is on it’s side – damn!). Click on the Key Color eyedropper icon and select the green collar in the Effect Control preview window. Then select the Plus (+) eyedropper icon below and click on the slightly different greens.

Eventually you’ll end up with this:

Now you need to add a mask to remove my head. As I’m moving you will need to animate the mask using keyframes. Do this by clicking on this icon on your new mask:

A little diamond will appear on the mask on that frame in the timeline. Move the Time Marker through the frames until you find a big change in speed and/or direction. Move the mask points to the new position. Notice this creates a new keyframe automatically. If you move the Time Marker between these two points you’ll notice the mask moves from the first position to the second

Repeat this until my head is rubbed out. Set a few keys to begin with, then go inbetween these keys and adjust accordingly, making the mask follow my head

Eventually you’ll finish, perhaps adding more masks with more feathering as you see fit. Make sure you’re constantly previewing and tweaking as necessary. If the movement is fast and blurs, keyframe an increase in the feathering and add more mask keys. Below is a GIF anim of the keys I used (without the inbetweens):

Now select Composition > Make Movie and note the name of the output file. You can then load this into your GIF anim creator, e.g. ImageReady . Alternatively, if you click on Output Module in the Render Queue window you can choose to output your film as an Animated GIF rather than Video For Windows. Selecting this option does not give you the control a dedicated GIF optimiser has, but is useful nonetheless

Don’t worry about some of the keys in my example file falling between frames, this is because I had to halve the frame rate of the rushes to make the file small enough to download. The original used the 25fps PAL resoulution video straight from my camcorder

The Camera
Frame the action so that you can see everything. Use a tripod and keep the camera still for the duration of the shooting

The most important aspect of my films is having a background without me in, so I can rub parts of myself out. This is called a backplate. So the first step is to film the backplate, without me/any props that will change in it

Be careful of changes in the lighting, as it will affect the backplate. The easiest is to either black the room out or film it at night time using artificial light. That way the light will stay exactly the same. Digital camera chips need a lot of light to stop the footage being noisy so the brighter the lights the better

It’s important to either use lamp shades or bounce the lights off walls to diffuse it – lots of harsh shadows can potentially make a five minute masking job take hours. For this film I used two lights, the main light and a little halogen light pointing at the wall:

When it comes to filming, don’t be afraid to reshoot as necessary. A bit of thought can save you a lot of time when it comes to doing the special effects. Notice in the rushes I did a few takes, just in case one wasn’t right

Use the best quality camera you can, a camcorder is best as it has a higher resolution and frame rate than the movie function on most digital cameras. Try to use the frame feature on your camcorder to remove the interlaced fields, otherwise you will need to use the deinterlace function in your editing program

If you haven’t got much room to shoot your action, try the same technique I used on this film of rotating the camera through 90º. This is only really useful for making gif anims or videos for the computer screen, as no one is going to be willing to rotate their television round 90º just to watch your one film (unless they all tilt their heads of course). You can potentially letterbox your film, but it’s not ideal