We use a digital audio recorder for our Stubborn Old Gardeners videos. It provides noticeably better sound than we would get from the onboard microphone on our camcorder, but it requires a separate step, namely that the sound from the recorder be synchronized with the video picture. That’s where the slate board comes in.
Slate boards are s-o-o 20th century in professional film production today, because all the video and audio equipment is seamlessly integrated, and slating happens digitally. But for Stubborn Old Gardeners, the slate board provides a simultaneous visual cue (the picture of the boards popping together) and an audible cue (the slapping sound of the boards hitting each other). Using the two together, the videographer can quickly synchronize the camcorder video with the recorder audio.
Because we often need to stop, start, and re-record scenes, the slate board (together with the production assistant’s recording of the take we end up using) gives the videographer a quick way to locate the right audio and video, sync them up, and insert them into the video so they look and sound great.