Clapper loader

The specific responsibilities and division of labor within the department will almost always vary depending on the circumstances of the shoot.

[1] Clapper loaders have a very important role as practically the only people on set who directly and physically oversee the state of the undeveloped negative.

Additionally, the loader usually controls all records with regard to the film stock – from when it is received until when it is sent out to the lab; if this information is miscommunicated or missing, this too can destroy an expensive shoot.

[2] Noted director of photography Oliver Stapleton has written on his website: The LOADER loads the camera, oddly enough, with film made by either Kodak or Fuji.

Kubrick fired one loader I know on his first day of work for walking across the set holding a magazine upside down.

Clapper loader operating the clapperboard during the filming of A Place in the Caribbean (2017, Honduras)
Panavision R-200 movie camera (through-the-lens Reflex, 200 degree shutter, hence R-200). The camera magazine is inside the lighter color "blimp" on the top of the camera; the camera head is inside the darker color "blimp" on the bottom; the camera magazine can be removed to be reloaded by the clapper loader
A strip of undeveloped 35 mm color negative film from a roll; B&W negative film is similar; "Negative" may be inferred from the BH style perforations.
Each 35 mm roll contains a maximum of 2,000 feet, or 22.22 minutes of running time at 24 fps , with a customary maximum of 18–19 minutes.
Digital Clapperboard