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Sprockets: Difference between revisions
→Sprocket Design By Film Gauge: Added images of VKF and Posi-Trol sprockets.
JesseCrooks (talk | contribs) (→35mm) |
JesseCrooks (talk | contribs) (→Sprocket Design By Film Gauge: Added images of VKF and Posi-Trol sprockets.) |
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[[File:KS as CS sprockets (standing).JPG|right|thumb| | [[File:KS as CS sprockets (standing).JPG|right|thumb|400px]] | ||
Sprockets are toothed drums that engage with the [[perforations]] (also called '''sprocket holes''') to advance the film through the projector. | Sprockets are toothed drums that engage with the [[perforations]] (also called '''sprocket holes''') to advance the film through the projector. | ||
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====LaVezzi Posi-Trol==== | ====LaVezzi Posi-Trol==== | ||
After the use of CS perfs died out in the early 1980s, LaVezzi redesigned their VKF sprockets to only accommodate film with KS perforations. They recentered the sprocket teeth to align with KS perfs and widened the teeth on one side to fill more of the width of the perforation. This “positive control” resulted in increased horizontal stability. However, these sprockets cannot be used with CS perfs, and can present issues with shrunken KS perfs. As a result, they are not recommended for archival projection. | After the use of CS perfs died out in the early 1980s, LaVezzi redesigned their VKF sprockets to only accommodate film with KS perforations. They recentered the sprocket teeth to align with KS perfs and widened the teeth on one side to fill more of the width of the perforation. This “positive control” resulted in increased horizontal stability. However, these sprockets cannot be used with CS perfs, and can present issues with shrunken KS perfs. As a result, they are not recommended for archival projection. | ||
<gallery widths=150px heights=150px mode=packed> | |||
File:CS and VKF sprocket teeth.png|A comparison of CS and VKF sprocket teeth, shown within a CS perf (black) and KS perf (white). | |||
File:Posi-Trol sprocket teeth.png|Posi-Trol sprocket teeth, shown within KS perfs. | |||
</gallery> | |||
===16mm=== | ===16mm=== | ||
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===Dual-Gauge=== | ===Dual-Gauge=== | ||
[[File:Century JJ Intermittent.JPG|right|thumb| | [[File:Century JJ Intermittent.JPG|right|thumb|400px|The dual-gauge intermittent sprocket on a Century JJ, attached to the intermittent mechanism.]] | ||
Sprockets designed for [[dual-gauge projectors]] have two sets of teeth. Teeth for the larger gauge are located on the outside edge of the sprocket, while teeth for the smaller gauge are recessed in the center of the sprocket at a smaller diameter. The difference in diameter allows the film to be transported at the correct speed without adjusting the projector’s drive speed. For example, the combined intermittent sprocket for a 35/70 projector will advance 35mm film by four perforations per step while 70mm film is advanced five perforations per step. | Sprockets designed for [[dual-gauge projectors]] have two sets of teeth. Teeth for the larger gauge are located on the outside edge of the sprocket, while teeth for the smaller gauge are recessed in the center of the sprocket at a smaller diameter. The difference in diameter allows the film to be transported at the correct speed without adjusting the projector’s drive speed. For example, the combined intermittent sprocket for a 35/70 projector will advance 35mm film by four perforations per step while 70mm film is advanced five perforations per step. | ||