Editing 35 mm movie film (section)

===KS perforations===
Because BH has sharp corners, the repeated use of the film through intermittent movement projectors creates strain that can easily tear the perforations. Furthermore, they tended to shrink as the print slowly decayed. Therefore, larger perforations with a rectangular base and rounded corners were introduced by [[Kodak]] in 1924 to improve steadiness, registration, durability, and longevity. Known as "Kodak Standard" (KS), they are {{convert|0.0780|in|mm}} high by {{convert|0.1100|in|mm}} wide.<ref name="smpte139">{{cite book|title=ST 139:2003 - SMPTE Standard - For Motion-Picture Film (35-mm) — Perforated KS|date=12 November 2003|publisher=[[SMPTE]]|isbn=978-1-61482-313-1|doi=10.5594/SMPTE.ST139.2003}}</ref> Their durability makes KS perfs the ideal choice for some (but not all) intermediate and all release prints, and [[original camera negative]]s which require special use, such as high-speed filming, but not for [[Chroma key|bluescreen]], [[front projection]], [[rear projection]], or [[Matte (filmmaking)|matte]] work as these specific applications demand the more accurate registration which is only possible with BH or DH perforations. The increased height also means that the image registration was considerably less accurate than BH perfs, which remains the standard for negatives.<ref name="JSMPE May 1930">{{cite journal |author=Society of Motion Picture Engineers |date=May 1930 |title=Standards Adopted by the Society of Motion Picture Engineers |url=https://archive.org/stream/journalofsociety14socirich#page/552/mode/2up |journal=Journal of the Society of Motion Picture Engineers |volume=XIV |issue=5 |pages=545–566}}</ref><ref name="screensound">{{cite web |work=ScreenSound Australia |url=http://www.nfsa.afc.gov.au/preservation/audiovisual_terms/audiovisual_item.php?term=Perforations |title=Technical Glossary of Common Audiovisual Terms: Perforations |access-date=August 11, 2006 |archive-url=https://web.archive.org/web/20071031093815/http://www.nfsa.afc.gov.au/preservation/audiovisual_terms/audiovisual_item.php?term=Perforations |archive-date=October 31, 2007}}</ref> The KS1870 perforation, or KS perforation with a [[Film perforations#Pitch|pitch]] of {{convert|0.1870|in|mm}}, is the modern standard for release prints.<ref name="Kodak motion film specs" />

These two perforations have remained by far the most commonly used ones. BH perforations are also known as ''N'' (negative) and KS as ''P'' (positive). The Bell & Howell perf remains the standard for camera negative films because of its perforation dimensions in comparison to most printers, thus it can keep a steady image compared to other perforations.<ref name="Kodak motion film specs" /><ref name="gray">{{cite web |url=http://www.jkor.com/peter/perfs.html |title=Perforations/Sprocket Holes: Peter Gray - Director of Photography |year=1997 |access-date=March 14, 2012 |last=Gray |first=Peter |archive-url=https://web.archive.org/web/20080412041026/http://www.jkor.com/peter/perfs.html |archive-date=April 12, 2008}}</ref>