Updated: a day ago
This blog assumes you know the basics of After Effects! If not, do consider learning it. It’s an incredible program.
But for those of you who understand the basic terminology, start by making a composition based on HDTV 1080 25 with a black fill, a length of 10 seconds, and a frame rate of 25 fps.
Then double-click on the Text tool. This automatically puts a cursor in the middle of the screen. Type the words ‘BLACK – WHITE’. I think this is most effective if you use a fairly bold typeface (Arial Black?), and give it a white fill. Size: somewhere around 135 pixels. The leading (space between the lines) doesn’t matter, as this project only uses a single line of text. It’s probably sitting on a baseline that runs through the centre of the screen, which means it’s a bit high. Drag it down slightly (with the Selection tool) to make it more central. You don’t have to do this, but you might think it looks a bit more balanced in the end if you do.
NOTE: When you move the text, make sure ‘caps lock’ isn’t on, or you’ll have all kinds of trouble.
Normally, type is measured in point size, but not in After Effects. Everything in AE is intended for screen viewing. That makes pixels a much more reasonable unit of measurement.
Then choose ‘layer > new > solid’. Make it white, 600 x 400 pixels. It will appear in the middle of the composition screen.
Press ‘P’ to open its position settings. Put the playhead right at the start of the animation, drag the solid so it’s just off the screen to the left, and click on the little stopwatch to the left of the word ‘position’ to create a keyframe.
Then move the playhead to the 5 second marker and drag the rectangle until it’s just off the screen on the right hand side. If you hold down the ‘shift’ key after you start dragging, it’s constrained to follow a horizontal line. But that won’t work if you hold down the ‘shift’ key before you start dragging.
Because you already created a keyframe by clicking on the stopwatch, another is automatically created at this point.
Now hold down the ‘alt’ key and click on the stopwatch again. A new line appears in the Timeline (the area to the right of the layers) in which you should type the following:
It’s got to be exact. If it’s not exactly as shown here, it won’t work. So, only the ‘O’ of ‘Out’ is capitalised. The quotes are double quotes, not single quotes. This is action script: either it’s perfect, or it’s wrong. In After Effects, things like this are called ‘expressions’, and this one makes the animation repeat backwards and forwards. in a loop.
Drag the playhead back to the start and press the spacebar to start it running.
The white rectangle appears and moves right across the screen and off, then re-appears and moves from right to left, and off. Again and again. If you hadn’t added the expression, the rectangle would just move in from the left, travel across the screen, and...it would be gone. It wouldn’t return.
Press the spacebar again to stop the animation running. Then change the ‘blending mode’ of the text layer from ‘normal’ to ‘subtract’.
Where it’s touched by the white rectangle, it becomes black. And as the rectangle moves away from it, it becomes white again.
And that’s it! It’s an interesting and effective little animation, and it uses a very simple mix of blending modes and expressions, both of which are normally quite advanced features.