Film perforations
Encyclopedia
Film perforations, also known as perfs, are the holes placed in the film stock
during manufacturing and used for transporting (by sprocket
s and claws) and steadying (by pin registration
) the film
. Films may have different types of perforations depending on film gauge
, film format
, and the intended usage. Perforations are also used as a standard measuring reference within certain camera systems to refer to the size of the frame.
Some formats are in fact referred to as (perforations per frame/gauge size) to give an easy way of denoting this. For instance, VistaVision
is also known as (8/35), while standard 70 mm film
is (5/70) as compared to IMAX
, which is (15/70). This system does not indicate whether the film transport is horizontal or vertical, but there are currently no horizontal systems using the same number of perforations on the same gauge as a vertical one.
and 16 mm film
, there are two different pitches - short pitch (camera stocks intended for duplication or printing, most intermediate applications) and long pitch (camera stocks intended for direct projection, print stocks, special intermediate applications). For 35 mm these are 0.1866" and 0.1870" (4.740 mm and 4.750 mm); for 16 mm they are 0.2994" and 0.3000" (7.605 mm and 7.620 mm).
work as these specific applications demand the more accurate registration which is only possible with BH or DH perforations. KS perfs are rectangular with rounded corners, and measure 0.0780" (1.981 mm) high by 0.1100" (2.794 mm) wide.
KS perforations were once recommended for negative and intermediate films, too, but only the Eastern Bloc countries (the Soviet Union and its Satellites) adopted KS for these uses. The Western Bloc countries maintained BH perforations for negative and intermediate films, but adopted KS perforations for positive print films and for amateur films which were on a 35mm wide base.
This is perhaps one of the very few instances where a Western Bloc recommendation and standard was adopted by the Eastern Bloc, but was soundly rejected by the very Bloc which proposed its adoption. To this day, all Western Bloc professional cameras employ BH perforations, and so also do its intermediate applications (interpositives and internegatives).
One aspect of this particular adoption was it effectively prevented amateur camera films from being "diverted" to professional uses, as KS-perforated camera film will indeed pass undamaged through a Western Bloc professional camera, but it cannot maintain the expected and required registration accuracy as the KS perforation is too tall, relative to the professional camera's BH-sized registration pin(s).
The increased height also means that the image registration was considerably less accurate than BH perfs, which remains the standard for negatives. The KS1870 perforation, or KS perforation with a pitch of 0.1870", is the modern standard for release prints, as well as for 135 still camera film
.
65/70mm, the other "professional" standard, was created many years after KS perforations had been recommended for negative as well as positive applications, and had been adopted for positive applications. Consequently, 65/70mm uses only KS perforations for all applications, negative, intermediate and positive.
's dye imbibition printing (dye transfer). The DH perf never caught on, and Kodak's introduction of monopack Eastmancolor film in the 1950s reduced the demand for dye transfer, although the DH perf persists in intermediate films to this day, such as long-pitch interpositives contact-printed from short-pitch negatives.
films were made by 20th Century Fox
). Their dimensions are 0.0780" (1.85 mm) in width by 0.0730" (1.98 mm) in height.
Due to the size difference, CS perfed film cannot be run through a projector with standard KS sprocket teeth, but KS prints can be run on sprockets with CS teeth (see VKF, below). Although CS perfs have not been widely used since the late 1950s, and only occasionally until the late 1970s, Kodak still retains CS perfs as a special-order option on at least one type of print stock.
and Universal
, for location dialogue recording and it was most often run at 45 feet/minute, one-half of the 35mm magnetic film speed, thereby achieving a 4-to-1 increase in economy although at a significant sacrifice in sound fidelity, but certainly adequate for monophonic dialogue. For stereophonic dialogue, 35mm magnetic film was used.
uses 16 mm film that is perforated twice as frequently (half the pitch of normal 16 mm) and then split down the middle after development. Super 8
uses slightly smaller perfs on film which is already 8 mm wide. Super 8 pitch is 0.1667" and perfs are 0.045" high by 0.036" wide.
Some obsolete formats such as 9.5 mm film
and some variants of 17.5 mm film used a single perforation in the middle of the frame line between each image. This is considered more of a liability however, since any sprocket or claw error will likely damage the center of the frame itself rather than the outer edges.
Film stock
Film stock is photographic film on which filmmaking of motion pictures are shot and reproduced. The equivalent in television production is video tape.-1889–1899:...
during manufacturing and used for transporting (by sprocket
Sprocket
A sprocket or sprocket-wheel is a profiled wheel with teeth, cogs, or even sprockets that mesh with a chain, track or other perforated or indented material. The name 'sprocket' applies generally to any wheel upon which are radial projections that engage a chain passing over it...
s and claws) and steadying (by pin registration
Registration pin
A registration pin is a device intended to hold a piece of film, paper or other material in place during photographic exposure, copying or drawing....
) the film
Film
A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects...
. Films may have different types of perforations depending on film gauge
Film gauge
Film gauge is a physical property of photographic or motion picture film stock which defines its width. Traditionally the major film gauges in usage are 8 mm, 16 mm, 35 mm, and 65/70 mm...
, film format
Film format
A film format is a technical definition of a set of standard characteristics regarding image capture on photographic film, for either stills or movies. It can also apply to projected film, either slides or movies. The primary characteristic of a film format is its size and shape.In the case of...
, and the intended usage. Perforations are also used as a standard measuring reference within certain camera systems to refer to the size of the frame.
Some formats are in fact referred to as (perforations per frame/gauge size) to give an easy way of denoting this. For instance, VistaVision
VistaVision
VistaVision is a higher resolution, widescreen variant of the 35mm motion picture film format which was created by engineers at Paramount Pictures in 1954....
is also known as (8/35), while standard 70 mm film
70 mm film
70mm film is a wide high-resolution film gauge, with higher resolution than standard 35mm motion picture film format. As used in camera, the film is wide. For projection, the original 65mm film is printed on film. The additional 5mm are for magnetic strips holding four of the six tracks of sound...
is (5/70) as compared to IMAX
IMAX
IMAX is a motion picture film format and a set of proprietary cinema projection standards created by the Canadian company IMAX Corporation. IMAX has the capacity to record and display images of far greater size and resolution than conventional film systems...
, which is (15/70). This system does not indicate whether the film transport is horizontal or vertical, but there are currently no horizontal systems using the same number of perforations on the same gauge as a vertical one.
Pitch
One of the characteristics of perforations is their "pitch". This is the measurement of the distance between the top of two perforations in sequence. For motion picture 35 mm film35 mm film
35 mm film is the film gauge most commonly used for chemical still photography and motion pictures. The name of the gauge refers to the width of the photographic film, which consists of strips 35 millimeters in width...
and 16 mm film
16 mm film
16 mm film refers to a popular, economical gauge of film used for motion pictures and non-theatrical film making. 16 mm refers to the width of the film...
, there are two different pitches - short pitch (camera stocks intended for duplication or printing, most intermediate applications) and long pitch (camera stocks intended for direct projection, print stocks, special intermediate applications). For 35 mm these are 0.1866" and 0.1870" (4.740 mm and 4.750 mm); for 16 mm they are 0.2994" and 0.3000" (7.605 mm and 7.620 mm).
Shapes
BH
Additionally, in 35 mm, only, there are several different shapes for these perforations. BH (Bell and Howell) perforations are used in camera negative film and have straight top and bottom with outward curving sides and have been in use since the very beginning of the 20th century. The BH perforation's dimensions are 0.110" (2.79 mm) from the middle of the side curve to opposite top corner by 0.073" (1.85 mm) in height. The corners used to be sharp, but were slightly rounded in 1989 by 0.005" (0.127 mm) to give them greater strength. The BH1866 perforation, or BH perforation with a pitch of 0.1866", is the modern standard for negative and intermediate (interpositive and internegative) films, and the BH1870 perforation, or BH perforation with a pitch of 0.1870", was the original standard for positive prints for direct projection (release prints).KS
KS (Kodak Standard) perforations were introduced in the 1920s to improve steadiness, registration, durability, and longevity and thus are occasionally used for high-speed filming, but not for bluescreen, front projection, rear projection, or matteMatte
Matte may refer to:In film:* Matte , filmmaking and video production technology* Matte painting, a process of creating sets used in film and video* Matte box, a camera accessory for controlling lens glare...
work as these specific applications demand the more accurate registration which is only possible with BH or DH perforations. KS perfs are rectangular with rounded corners, and measure 0.0780" (1.981 mm) high by 0.1100" (2.794 mm) wide.
KS perforations were once recommended for negative and intermediate films, too, but only the Eastern Bloc countries (the Soviet Union and its Satellites) adopted KS for these uses. The Western Bloc countries maintained BH perforations for negative and intermediate films, but adopted KS perforations for positive print films and for amateur films which were on a 35mm wide base.
This is perhaps one of the very few instances where a Western Bloc recommendation and standard was adopted by the Eastern Bloc, but was soundly rejected by the very Bloc which proposed its adoption. To this day, all Western Bloc professional cameras employ BH perforations, and so also do its intermediate applications (interpositives and internegatives).
One aspect of this particular adoption was it effectively prevented amateur camera films from being "diverted" to professional uses, as KS-perforated camera film will indeed pass undamaged through a Western Bloc professional camera, but it cannot maintain the expected and required registration accuracy as the KS perforation is too tall, relative to the professional camera's BH-sized registration pin(s).
The increased height also means that the image registration was considerably less accurate than BH perfs, which remains the standard for negatives. The KS1870 perforation, or KS perforation with a pitch of 0.1870", is the modern standard for release prints, as well as for 135 still camera film
135 film
The term 135 was introduced by Kodak in 1934 as a designation for cartridge film wide, specifically for still photography. It quickly grew in popularity, surpassing 120 film by the late 1960s to become the most popular photographic film format...
.
65/70mm, the other "professional" standard, was created many years after KS perforations had been recommended for negative as well as positive applications, and had been adopted for positive applications. Consequently, 65/70mm uses only KS perforations for all applications, negative, intermediate and positive.
DH
The Dubray Howell (DH) perforation was first suggested in 1931 to replace both the BH and KS perfs with a single standard perforation which was a hybrid of the two in shape and size, being like KS a rectangle with rounded corners and a width of 0.1100" (2.79 mm), but with BH's height of 0.073" (1.85 mm). This gave it longer projection life but also improved registration. One of its primary applications was usage in TechnicolorTechnicolor
Technicolor is a color motion picture process invented in 1916 and improved over several decades.It was the second major process, after Britain's Kinemacolor, and the most widely used color process in Hollywood from 1922 to 1952...
's dye imbibition printing (dye transfer). The DH perf never caught on, and Kodak's introduction of monopack Eastmancolor film in the 1950s reduced the demand for dye transfer, although the DH perf persists in intermediate films to this day, such as long-pitch interpositives contact-printed from short-pitch negatives.
CS
In 1953, the introduction of CinemaScope required the creation of a different shape of perforation which was nearly square and smaller to provide space for four magnetic sound stripes for stereophonic and surround sound. These perfs are commonly referred to as CinemaScope (CS) or "Fox hole" perforations, or simply "Foxholes" (because, initially, all CinemascopeCinemaScope
CinemaScope was an anamorphic lens series used for shooting wide screen movies from 1953 to 1967. Its creation in 1953, by the president of 20th Century-Fox, marked the beginning of the modern anamorphic format in both principal photography and movie projection.The anamorphic lenses theoretically...
films were made by 20th Century Fox
20th Century Fox
Twentieth Century Fox Film Corporation — also known as 20th Century Fox, or simply 20th or Fox — is one of the six major American film studios...
). Their dimensions are 0.0780" (1.85 mm) in width by 0.0730" (1.98 mm) in height.
Due to the size difference, CS perfed film cannot be run through a projector with standard KS sprocket teeth, but KS prints can be run on sprockets with CS teeth (see VKF, below). Although CS perfs have not been widely used since the late 1950s, and only occasionally until the late 1970s, Kodak still retains CS perfs as a special-order option on at least one type of print stock.
VKF
LaVezzi Precision Inc (999 Regency Drive, Glendale Heights, IL 60139) has developed a composite sprocket design, dubbed VKF ("Very Kind to Film"), which is at home driving CinemaScope-perforated films as it is driving Kodak Standard-perforated films. The sprocket teeth are shaped in a proprietary way to reduce print film wear while ensuring smooth engagement and disengagement of the perforated edge with the tooth surface, whether CS or KS perforations are employed. VKF sprockets are available for most projectors.17.5 mm
17.5 mm magnetic film corresponds to 35mm magnetic film which had been slit lengthwise into two equal widths and lengths. The "heads" of the 35mm donor became the "heads" of one 17.5mm length while the "tails" of the 35mm donor became the "heads" of the other 17.5mm length. 17.5mm magnetic film was occasionally used as a secondary "shop standard", perhaps most notably at ParamountParamount Pictures
Paramount Pictures Corporation is an American film production and distribution company, located at 5555 Melrose Avenue in Hollywood. Founded in 1912 and currently owned by media conglomerate Viacom, it is America's oldest existing film studio; it is also the last major film studio still...
and Universal
Universal Pictures
-1920:* White Youth* The Flaming Disc* Am I Dreaming?* The Dragon's Net* The Adorable Savage* Putting It Over* The Line Runners-1921:* The Fire Eater* A Battle of Wits* Dream Girl* The Millionaire...
, for location dialogue recording and it was most often run at 45 feet/minute, one-half of the 35mm magnetic film speed, thereby achieving a 4-to-1 increase in economy although at a significant sacrifice in sound fidelity, but certainly adequate for monophonic dialogue. For stereophonic dialogue, 35mm magnetic film was used.
16 mm
All 16 mm perforations are rectangles with rounded corners and are 0.0500" high by 0.078" wide. The tolerance for these perforation dimensions was reduced to 0.01 mm in 1989, which allowed 16 mm camera manufacturers to slightly enlarge their registration pins and thus improve image registration and steadiness tolerances to less than 1/750th of the image height of the 16 mm frame.8 mm
Standard 8 mm film8 mm film
8 mm film is a motion picture film format in which the filmstrip is eight millimeters wide. It exists in two main versions: the original standard 8mm film, also known as regular 8 mm or Double 8 mm, and Super 8...
uses 16 mm film that is perforated twice as frequently (half the pitch of normal 16 mm) and then split down the middle after development. Super 8
Super 8 mm film
Super 8 mm film is a motion picture film format released in 1965 by Eastman Kodak as an improvement of the older "Double" or "Regular" 8 mm home movie format....
uses slightly smaller perfs on film which is already 8 mm wide. Super 8 pitch is 0.1667" and perfs are 0.045" high by 0.036" wide.
Placement
All of the systems described above place the perforations down either one side (Standard and Super 8, Super 16) or both sides (35 mm and 65/70 mm). Standard 16 mm can be either (single or double perf); some older cameras require double perf, but most can handle either. Because most cameras can handle both and increased popularity of Super 16, most 16 mm stock manufactured today is single perf unless requested otherwise.Some obsolete formats such as 9.5 mm film
9.5 mm film
9.5 mm film is an amateur film format introduced by Pathé Frères in 1922 as part of the Pathé Baby amateur film system. It was conceived initially as an inexpensive format to provide copies of commercially-made films to home users, although a simple camera was released shortly afterwards.It...
and some variants of 17.5 mm film used a single perforation in the middle of the frame line between each image. This is considered more of a liability however, since any sprocket or claw error will likely damage the center of the frame itself rather than the outer edges.
Damage and inspection
Damaged or broken perforations can lead to a tear in the film as it runs through the projector. Film is commonly checked for broken sprocket holes before presentation, a process known as "spooling". Mechanical devices exist for this, but the classic method is to place finger and thumb of a gloved hand on the edges of the film mounted on a winding bench and slowly run the film through the fingers, feeling for snags.See also
- 3-perf and 2-perf pulldown
- 35mm film
- List of film formats
- Super 35 mm filmSuper 35 mm filmSuper 35 is a motion picture film format that uses exactly the same film stock as standard 35 mm film, but puts a larger image frame on that stock by using the negative space normally reserved for the optical analog sound track.Super 35 was revived from a similar Superscope variant known as...