Film gate - Citizendia

The film gate is the rectangular opening in the front of a motion picture camera where the film is exposed to light. This article is about motion picture film cameras See Video camera for cameras which record images electronically The film gate can be seen by removing the lens and rotating the shutter out of the way. A photographic lens (also known as objective lens or photographic objective) is an optical lens or assembly of lenses used in conjunction with Motion picture cameras film is exposed as a pie-shaped mirror called a rotary disc shutter, rotates in front of the Film gate. The film is held on a uniform plane at a calibrated distance in the gate by a pressure plate behind the film.

As the film passes through the gate occasionally friction can cause small slivers of celluloid to break off and stick in the side of the opening. This debris is called hairs. A "hair in the gate" will remain in front of the film and create a dark line that sticks into the edge of the film frame as the camera is filming a shot. A hair can ruin the shot and is almost impossible to fix in post production without being painted out digitally. See also Filmmaking Post-production occurs in the making of motion pictures, television programs, Videos audio recordings

Because of the intractability of this problem the 1st Assistant Camera (in the UK this position is known as focus puller) will open the camera and examine the gate for hairs at the end of each shot. In Cinematography, a focus puller or first assistant camera (1st AC is the member of a Film crew responsible for keeping the Camera 's focus Normally the assistant director will call out "check the gate" when the director is ready to move on to the next shot. An assistant director (AD is a person who helps the director in the making of a Movie or Television show The crew will wait until the focus puller calls out "gate is clean". If the gate is not clean, it will be cleaned with orangewood sticks and canned air and the crew will take the shot again. A gas duster, also erroneously referred to as canned air, is a product consisting of liquefied Difluoroethane, trifluoroethane, or Tetrafluoroethane A good camera crew usually checks all cameras and magazines during equipment checkout with scratch tests using fogged film rolls - this will catch out any possible scratch or hair problems caused by faulty equipment. A camera magazine is a light-tight chamber or pair of chambers designed to hold and move Motion picture Film stock before and after it has been exposed in the camera However, a variety of other factors including environment, humidity, type of film stock, camera position, film ridging, and lacing can each be responsible for a "hair in the gate". Generally, skilled crew and regularly inspected tested equipment make this a rare occurrence, and it is not unheard of for assistants to go for months without seeing one, even on large-scale shoots. The cinematographer Oliver Stapleton recently praised his assisting team on Casanova for not having a single hair or scratch for the whole shoot, even though large portions were shot on dusty exteriors [1]. Casanova is a 2005 American Romantic comedy Film directed by Lasse Hallström based on the life of Giacomo

Video cameras do not have this problem, as any malfunction to the sensor will render the entire system useless. The new Arri D-20 system, however, does have removable lenses and a rotating optical shutter, which does mean that the CMOS sensor can be exposed in much the same way as a film gate and thus needs to be kept assiduously clean. The Arri Group has been the largest world wide supplier of high quality Motion picture film equipment since 1917

1 Methods of checking the gate
2 See also

Methods of checking the gate

There are three different commonly accepted ways to check a film gate for hairs. Some may be better for certain logistical reasons than others on particular shots, and different assistants have different preferences for which to use first. It should also be noted that if a hair is in the gate but outside of the aspect ratio being filmed (if for instance, there was a tiny speck at the bottom of a full 1. 37 ratio gate but it was framed for 1. 85 with common center), the hair may not always be considered enough of a problem, though usually any evidence of one is enough not to risk a lost shot.

Pulling the lens

In this method, the lens is taken off of the camera and the shutter is moved either with an automatic button (usually labeled "phase" or "dust check") or by manually inching it to an exposed position. The focus puller examines the gate with a flashlight, sometimes attached to a magnifying glass. A flashlight (also called an electric torch or torch) is a portable electric spotlight which emits light from a small incandescent Lightbulb

Through the lens

This method tends to be most useful on long lenses and zoom lenses, especially when larger lenses may be difficult to take on and off again quickly. The aperture is fully opened, with the shutter opened, focus set to infinity, and if a zoom, zoomed in as tight as possible. The lens itself acts as a large magnifying glass for the focus puller, who only needs to position the flashlight and his line of sight properly to scan the gate.

Pulling the gate

Many cameras, though not all, allow for the gate itself to be removed from the camera and examined under a light by the focus puller.

Contents

Methods of checking the gate

Pulling the lens

Through the lens

Pulling the gate

See also