Understanding the background color

I thought it would be helpful to explain the significance of the background color to After Effects. This composition has a black background color. The background color indicates which areas are transparent. You can also see which areas of the comp are transparent by selecting the alpha channel from the RGB channels pop-up. Any areas that are solid white are fully opaque. Any areas that are black indicate full transparency. Wherever you see shades of gray, you are looking at shades of transparency.

I will toggle off the alpha channel and turn off the transparency grid. Now sometimes the black background color is not that useful. You can change it in CS5 under Composition settings; in CS4, Background Color is a menu item under Composition. So if I change the background color to white, I can clearly see the drop shadow effects on the video layers and the title. Just to make it clear that the background color is transparency, let me create a new solid layer.

I will make this white, and any size will do. There is my white solid. If I align the solid to the top of the comp, I can't see the difference between the white solid and the white background, unless I turn on the transparency grid, or view the alpha channel. Now, you can see the white solid exists in RGB color space, just like the videos.

So by all means, go ahead and change the background color to whatever color is most useful, but be aware that if you render with an alpha channel, the background color will be the transparent areas. Let me delete the white solid, and show you one more example. In my second composition, I have a row of snowflakes on a blue background. The blue was created with the background color. Now we haven't done nesting yet; we will do that in a later lesson. But all I mean by nesting is that I can take the Snowflake composition in the Project panel and simply drag it to the main composition, just as if I'd drag in a movie.

However, you'll notice the blue background color has disappeared. That's because the blue background is transparency. So when I nest it, it drops out. If I want to see that blue background, I need to create it in RGB color space. I can do that with a solid layer or a shape layer. Now we will get to shape layers in the future lesson, so let's just create a solid layer since you know how to do that. On problem I found with eyedropper-ing a color is that it won't eyedropper the background color.

So if want this exact color, this is simple trick. I can open the Composition settings, click on the color swatch, and copy the value for that color. Now when I create a new solid, I can click on the color swatch and paste that value. The solid appears at the top of the comps, so I will just drag it down to the bottom. When I toggle on and off the solid, there is no difference in this comp between viewing the solid blue color and the background blue color. But there is a big difference when I return to the main composition.

Unlike the background color, the solid layer will be visible in the next comp. So I hope that explains a little more about background colors versus solid layers, and when you might need to use one versus the other.