Editing 135 film (section)

== Characteristics ==
{{More references needed|section|date=June 2023}}

=== Cassette ===
[[file:Kodak-Max-400-35mm-Film.jpg|upright|thumb|A roll of [[Kodak]] 135 film for cameras]]

Individual rolls of 135 film are enclosed in single-spool, light-tight, metal cassettes to allow cameras to be loaded in daylight. The film is clipped or taped to a spool and exits via a slot lined with [[Flocking (texture)|flocking]]. The end of the film is cut on one side to form a leader. It has the same dimensions and perforation pitch as [[35 mm movie film|35&nbsp;mm movie print film]] (also called "long pitch", [[Film perforations#KS|KS-1870]], whereas 35&nbsp;mm professional motion picture camera films are always "short pitch", [[Film perforations#BH|BH-1866]]).

Most cameras require the film to be rewound before the camera is opened. Some motorized cameras unwind the film fully upon loading and then expose the images in reverse order, returning the film to the cassette; this protects all exposed frames (except the last one or two), should the camera back be accidentally opened; unexposed film gets spoiled, however. [[Disposable camera]]s use the same technique so that the user does not have to rewind.

[[File:DX-Codierung asb PICT3739.JPG|thumb|right|This modern film canister uses [[DX encoding]]; it is marked with a six-digit barcode which embeds the [[DX number]] below a silver-and-black conductive DX Camera Auto Sensing pattern.]]
Since 1983, most film cassettes have been marked with a [[DX encoding]] six-digit [[barcode]] pattern, which uses a [[DX number]] to identify the manufacturer and film type (and thus processing method), and the number of exposures, for the use of photofinishing laboratories. The cassettes are also manufactured with a Camera Auto Sensing code constructed as two rows of six rectangular areas on the metal cassette surface which are either conductive or insulating, representing 32 possible film speeds, eight possible film lengths, and four possible values of exposure tolerance or latitude. Conforming cameras detect at least some of these areas; only three contacts are needed to set a light meter for the four most popular film speeds.

=== Film type and speed ===

The 135 film has been made in several emulsion types and sensitivities (film speeds) described by [[International Organization for Standardization|ISO]] standards. Since the introduction of digital cameras the most usual films have colour emulsions of ISO 100/21° to ISO 800/30°. Films of lower sensitivity (and better picture quality) and higher sensitivity (for low light) are for more specialist purposes. There are colour and monochrome films, negative and positive. Monochrome film is usually [[panchromatic]]; [[orthochromatic]] has fallen out of use. Film designed to be sensitive to infrared radiation can be obtained, both monochrome and with [[false-colour]] (or pseudocolour) rendition. More exotic emulsions have been available in 135 than other roll-film sizes.

=== Image format ===
[[file:135 film perforations.jpg|thumb|135 frame and perforations]]
[[file:Half-Frame 4442.jpg|thumb|Half-frame negatives (left and right) with standard 35&nbsp;mm (centre)]]

The term ''135 format'' usually refers to a 24×36&nbsp;mm [[film format]], commonly known as 35&nbsp;mm format. The 24×36&nbsp;mm format is common to higher-end digital [[image sensor]]s, where it is typically referred to as ''full-frame'' format.

On 135 film, the typical cameras produce a frame where the longer dimension of the 24×36&nbsp;mm frame runs parallel to the length of the film. The perforation size and pitch are according to the standard specification [[Film perforations#KS/P|KS-1870]]. For each frame, the film advances 8 perforations. This is specified as 38.00&nbsp;mm. This allows for 2&nbsp;mm gaps between frames. Camera models typically have different locations for the sprocket which advances the film. Therefore, each camera model's frame may vary in position relative to the perforations. The film is approximately 0.14&nbsp;mm thick.

Other image formats have been applied to 135 film, such as the [[Half-frame camera|half-frame]] format of 18×24&nbsp;mm which earned some popularity in the 1960s, and the 24×24&nbsp;mm of the [[Robot camera]]s. The successful range of [[Olympus Pen F]] cameras utilized the smaller half-frame size, allowing the design of a very compact SLR camera. Unusual formats include the 24×32&nbsp;mm and 24×34&nbsp;mm on the early Nikon [[rangefinder camera|rangefinders]], and 24×23&nbsp;mm for use with some [[stereo camera]]s. In 1967, the Soviet [[Krasnogorskiy Zavod|KMZ factory]] introduced a 24×58&nbsp;mm [[panoramic format]] with its Horizont camera (descendants of which are called, in the Roman alphabet, [[Horizon (camera)|Horizon]]). In 1998, [[Hasselblad]] and [[Fujifilm|Fuji]] introduced a 24×65&nbsp;mm panoramic format with their XPan/TX-1 camera. There is also a 21×14&nbsp;mm format used by Tessina subminiature camera.

=== Length ===
[[file:Ilford HP5 Autowinder film.jpg|thumb|A 72 exposure cartridge of Ilford HP5 film]]

The film is available in lengths for varying numbers of exposures. The standard full-length roll has always been 36 exposures (assuming a standard 24×36 frame size). Through about 1980, 20 exposure rolls were the only shorter length with widespread availability. Since then, 20 exposure rolls have been largely discontinued in favour of 24- and 12-exposure rolls. The length of the film provided includes the length required for the indicated number of exposures plus sufficient additional length for the film spoiled by being exposed to ambient light when it is drawn out of the canister, across the back of the camera, and securely engaged with the film advancing spool before the camera back is closed. A camera that uses less than the maximum distance between the spools may be able to make one additional exposure. Self-loading cameras that load the film after being closed don't spoil the additional length provided for conventional loading and can make that additional length available for two or three additional exposures. The same length can be available for exposure in any camera if it is loaded without exposing the film to light, e.g. in a dark room or a dark bag. A 27-exposure disposable camera uses a standard 24-exposure cassette loaded in the dark.

Other, mostly shorter, lengths have been manufactured. There have been some 6-, 8-, 10-, and 15-exposure rolls given away as samples, sometimes in disposable cameras, or used by insurance adjusters to document damage claims. Twelve-exposure rolls have been used widely in the daily press. Photographers who load their own cassettes can use any length of film – with a thinner film base, up to 45 exposures will fit.

The [[Ilford HP]] black-and-white film, on a thin polyester base, allowed 72 exposures in a single cassette.<ref>{{cite journal|title=Popular Photography|journal = Popular Photography |url=https://books.google.com/books?id=KXOfbgilEOAC&pg=PA68|date=February 1981|page=68|issn = 1542-0337}}</ref> They produced special reels and tanks to allow this to be processed.