Film Leader and Timecode
Film Leader
 

The head leader, at the beginning of each reel of film, comprises of a thread-up section that contains information about the reel’s content (such as film title, reel number, etc.). The countdown section begins with one frame that reads "PICTURE START", followed by a countdown, totaling 8 seconds (12 feet). The last visible frame of the countdown is the number "2" to denote the 2 second mark (3 feet) before the beginning of the first frame of picture. Keep in mind that the first frame of picture may begin with black.

The Academy leader contains one number per foot following PICTURE START, with 11, 10, etc., leading to 3. As projected, numbers are upside down. The SMPTE Universal leader is designed to be used primarily with videotape and features a sweep hand counting down in seconds from 8 to 2.
Sync Pop
  A single frame of 1 kHz tone is used as a guide to synchronize sound and picture. This sync pop on the resulting track negative creates a visual guide to the negative cutter, who uses it to make a printing start mark. The sync pop occurs two seconds before the first frame of picture, and thus corresponds to the "2" frame on the sweep-hand SMPTE Universal Leader, which counts down in seconds. On standard film leaders, the number at the pop is "3," because they count down in film footages.
How To Set Up Your Reels For Audio
 

Set video timecode per reel as follows:

Reel 1ab - PICTURE START frame = 01:00:00:00

Reel 2ab - PICTURE START frame = 02:00:00:00, etc.

The sync or 2-pop should occur at 6 seconds past the hour, or 0x:00:06:00, which lines up with the last number of the countdown. (2 on a SMPTE leader)

The end of a reel must be marked with one frame of "tail pop", occuring 2 seconds (3 feet) from the last frame of picture. A single frame of picture for sync reference, typically an upside down "2", should accompany the audio tail pop.

First frame of the movie must start at 8 seconds (0x:00:08:00), with no picture or sound from the movie occuring prior to this point. So if a reel begins with sound over black, then a sufficient amount of black must accompany the sound starting from the 8 second mark.