After watching the behind the scenes on a DVD I noticed something that I always wondered about when I see it. If you notice on the reel to reel cameras there’s usually (always??) a peice of tape going from the center of one reel to the center of the other. I think sometimes it has something written on it but sometimes not. I would assume that it is to differentiate between one reel and another, (ie red tape for this scene, blue for that scene), but it always seems to go exactly from the center of one to the center of the other. Any ideas? Hopefully this makes sense, I’m tired and rambling.
I’m not pcturing this. Unexposed film is in reels, but in light-sealed compartments outside the body of the camera. So you don’t see reels.
What you seem to be referring to (:p) is simply a label as to what shots are contained on that particular bit of film. Or an identification number for it. etc.
The Loader, or 2nd Assistand Cameraperson on smaller jobs has to label each load. They do so as they load the raw stock into the film magazine. That’s the large curved thing above the camera, if you are looking at a Panavision camera, the magazine is fairly large and flat.
One must make a label that will be used on the magazine, so that when that magazine of exposed negative is taken OFF the movie camera, and back to the person who will download that roll of film back INTO another film can, that label can travel with it, and be placed onto the can lid. This information is also duplicated on Lab Reports and such. The data on each exposed roll is SO priceless that there is much duplication of information regarding it, as a failsafe.
On your average movie, the label would look something like this. Some shows will have labels pre-printed showing some data already, it saves time and time is everything. Some Assistants will have the Production buy 3 inch wide white camera tape which has a template form printed right into it, and they will use that. Some prefer to hand write it all out themselves. Here is the basics:
RED DRAGON ( Show title goes on every single can )
5272 ( Type of film stock )
CR A-204 ( Camera Roll 204, shot on the “A” Body- the camera body used to shoot the bulk of a movie’s scenes )
3/23/01
Dev. Norm. ( Do not alter the normal developing bath at all )
Prep For Video Dailies ( Do not print a film image work print- basically movie footage that might be projected. These days, a lot of films have their negative developed and then only transfer those images to video for editing. Many films are not ‘cut’ on film any more, but are cut on computer-based non-linear editing systems ).
C. Tooniverse ( Always put your name on every roll you handle ).
Now, there MIGHT be another reason you are seeing a strip of tape that goes from feed side of a magazine to take-up side of a magazine. It’s a long shot but I’ve seen it. Some camera assistants ( anal compulsive breed that they are 
) will not only tape the magazine closed along the seam where the lid mounts to the body of the magazine, they will also run a strip of tape across both lid locks. On a Panavision magazine ( akin to the one you can see in the link ), there are two twist-locks. Some assistants tape with two smaller strips of tape, some run a long strip along the magazine to cover both twist locks. It’s redundant paranoia but then, any foot of film that has been shot but not yet developed is priceless.
The cost of the film is meaningless next to the cost of creating the images captured upon it. Hope this answers your question. 
Cartooniverse, who badly misses the scent of film.
…and, checking the gate…gates clean, all right folks, thats a wrap for today! Call time for tomorrow has been pushed ONE hour!
Oh my lord, my hero. A 1st A.C. with the power to push call time one hour. Lemme just buy you a beer please???