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Reels: Difference between revisions
Added section on reel capacity
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'''[[Split reel|Split reels]]''' are used when working with film on [[core|cores]] — for example, to transfer film from a core to a reel for exhibition. Split reels are not recommended for projection, but you should have one on your bench. They exist for all [[film gauges]]. | '''[[Split reel|Split reels]]''' are used when working with film on [[core|cores]] — for example, to transfer film from a core to a reel for exhibition. Split reels are not recommended for projection, but you should have one on your bench. They exist for all [[film gauges]]. | ||
==Reel Capacity== | |||
[[File:Goldberg film length indicator.JPG|right|thumb|300px|A 14” Golderg reel marked to indicate film length for acetate film.]] | |||
Reels are typically referred to by the length of film they can hold (ex., 35mm house reels are called 2,000’ reels). However, this nominal value is only an approximation. The actual capacity of a reel is determined by its hub size, flange diameter, and the thickness of the film. | |||
While the variation between reels that have a nominal capacity of 2,000’ is not great, this can become a factor when reels are overfilled beyond 2,000'. For example, when building up a reel of trailers, you may be able to fit more on the feed reel you’ve prepared than can fit on the take-up reel if it’s a different style, even though both are nominally 2,000’ reels. This variation is most easily demonstrated when dealing with split reels, since the capacity of the reel will vary based on core size selected. As an example of the range in capacity of nominal 2,000’ reels, a 15” split reel with a 2” core can hold roughly 2,729’ of polyester film, while a 15” Goldberg house reel with a 5” core can only hold 2,470’, and an older Goldberg house reel with a 14” diameter and a 4” hub can only hold 2,223’ of film. | |||
This becomes more of a factor when building up film to larger reels, or when handling prints that have been improperly broken down from large reels or platters, as some projectionists had the bad habit of breaking down a print by spooling onto each shipping reel until it seemed full (potentially overfilling it) and then cutting it at an arbitrary point instead of finding and separating the splices between reels. It is common for projectionists to refer to any reel that can fit 3-4 shipping reels as a 6,000’ reel, but the actual capacity can vary significantly. For example, a 25” Goldberg E-Z hub reel with an 8” hub can hold 6,938’ of polyester film while the same reel with a 5” hub can hold 7,409’. | |||
The variance from nominal capacity is also more of a consideration when comparing reel capacity for different film bases, since polyester is thinner than acetate, and acetate is thinner than nitrate. To a lesser extent there is also variation in base thickness between manufacturers. The thickness of the emulsion layer is another factor (this can be observed during projection when the change in depth causes the focus to drift between stocks). Magnetic tracks will also add to film thickness. | |||
===Roll Size Calculation=== | |||
The diameter of a roll of film can be devised using the following formula: | |||
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[[File:Film roll diameter formula.gif|left]] | |||
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Where: | |||
*D is roll diameter in inches | |||
*L is length of film roll in feet | |||
*t is film thickness in inches (about 0.0053 for Kodak 2383) | |||
*C is core/hub diameter in inches | |||
Alternatively, the total length of a roll of film or the total capacity for a reel can be calculated as: | |||
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[[File:Film roll length formula.gif|left]] | |||
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Examples of film thickness: | |||
*Kodak 2383 | |||
**Kodak 35mm polyester base thickness = 0.0047” | |||
**Kodak 2383 emulsion thickness = 0.0006” | |||
**Total thickness of Kodak 2382 stock = 0.0053” | |||
*Kodak 35mm triacetate base thickness = 0.0056” | |||
*Kodak 16mm triacetate base thickness = 0.00525” | |||
==Reels & film damage== | ==Reels & film damage== | ||