film leader is what you use to splice to the start and end of your reels to protect the film and attach it to its core. its papery texture on the painted/emulsion side makes it a happy medium for sharpies so you can identify what’s hiding on that core.
white painted leader is usually used as the head (beginning) leader. it’s spliced to the outside of the reel and identifying information, such as reel #, slate, take, etc, can be written on the leader itself. you can also write the information on paper tape stuck to the leader. paper tape is good to use because it can be easily removed and replaced with new information, allowing you to re-use the leader indefinitely.
red leader is typically used for the tail (end) of the reel. if the red leader is wrapped around your film, you know you’re gonna have to rewind that reel.
other colors of leader can be used to denote different uses/formats, for example, green for sound or blue for vistavision 8-perf. every film room has their own color code.
you can also use leader to indicate any gaps in your reel. say you’ve taken 12 frames out of your dailies roll so you can put those frames into your cut. first you cut out those 12 frames from your reel…
…and then you can then swap in 12 frames of leader with a little note as to where the frames went. later, when you get to that section in your reel, you’ll know at a glance how much is missing and where it went. this allows you to ctrl-z back to your missing footage.
thank you, painted leader, for protecting and defending our film from the elements!