I am new to learning After Effects, but have t good knowledge of Flash so I am familiar with the basic principles of motions graphics.
I am going through the book After Effects Apprentice.
I noticed that when I try to RAM Preview of the projects, some of them stop at 12 secoonds. I see the little green bar at the top stop at 12, when it should go to 30. It doesn't say anything about this in the book.
Though the entire 30 second movie will render fine.
I've cut and paste this answer by Todd Kopriva directly from another thread on the same topic:
RAM preview will only preview the number of frames that can fit into RAM---hence the name. The advantage is that the frames can be played back at (or near) real-time speed from RAM. If you want to preview more frames than can fit into RAM but sacrifice the speed of playback, use standard (spacebar) preview.
If you're just getting started with After Effects, I strongly recommend that you go through the materials linked to from the
After Effects Help and Support page, especially in the "Getting started" section.