You use actual to emphasize that you are referring to something real or genuine.
The segments are filmed using either local actors or the actual people involved.
这些片段是用当地的演员或真实的当事人拍摄的。
You use actual to contrast the important aspect of something with a less important aspect.
She had compiled pages of notes, but she had not yet got down to doing the actual writing.
她已辑录了多篇笔记,但她还没有着手实际的写作。