The aspect ratio of a geometric shape is the ratio of its sizes in different dimensions. For example, the aspect ratio of a rectangle is the ratio of its longer side to its shorter side—the ratio of width to height, when the rectangle is oriented as a "landscape".
ISO 216 is an international standard for paper sizes, used around the world except in North America and parts of Latin America. The standard defines the "A", "B" and "C" series of paper sizes, including A4, the most commonly available paper size worldwide. Two supplementary standards, ISO 217 and ISO 269, define related paper sizes; the ISO 269 "C" series is commonly listed alongside the A and B sizes.
35 mm film is a film gauge used in filmmaking, and the film standard. In motion pictures that record on film, 35 mm is the most commonly used gauge. The name of the gauge is not a direct measurement, and refers to the nominal width of the 35 mm format photographic film, which consists of strips 1.377 ± 0.001 inches (34.976 ± 0.025 mm) wide. The standard image exposure length on 35 mm for movies is four perforations per frame along both edges, which results in 16 frames per foot of film.
An envelope is a common packaging item, usually made of thin, flat material. It is designed to contain a flat object, such as a letter or card.
Paper size standards govern the size of sheets of paper used as writing paper, stationery, cards, and for some printed documents.
An f-number is a measure of the light-gathering ability of an optical system such as a camera lens. It is calculated by dividing the system's focal length by the diameter of the entrance pupil. The f-number is also known as the focal ratio, f-ratio, or f-stop, and it is key in determining the depth of field, diffraction, and exposure of a photograph. The f-number is dimensionless and is usually expressed using a lower-case hooked f with the format f/N, where N is the f-number.
135 film, more popularly referred to as 35 mm film or 35 mm, is a format of photographic film used for still photography. It is a film with a film gauge of 35 mm (1.4 in) loaded into a standardized type of magazine – also referred to as a cassette or cartridge – for use in 135 film cameras. The engineering standard for this film is controlled by ISO 1007 titled '135-size film and magazine'.
120 is a film format for still photography introduced by Kodak for their Brownie No. 2 in 1901. It was originally intended for amateur photography but was later superseded in this role by 135 film. 120 film survives to this day as the only medium format film that is readily available to both professionals and amateur enthusiasts.
126 film is a cartridge-based film format used in still photography. It was introduced by Kodak in 1963, and is associated mainly with low-end point-and-shoot cameras, particularly Kodak's own Instamatic series of cameras.
Medium format has traditionally referred to a film format in photography and the related cameras and equipment that use film. Nowadays, the term applies to film and digital cameras that record images on media larger than the 24 mm × 36 mm used in 35 mm photography, but smaller than 4 in × 5 in.
Large format refers to any imaging format of 9 cm × 12 cm or larger. Large format is larger than "medium format", the 6 cm × 6 cm or 6 cm × 9 cm size of Hasselblad, Mamiya, Rollei, Kowa, and Pentax cameras, and much larger than the 24 mm × 36 mm frame of 35 mm format.
Panoramic photography is a technique of photography, using specialized equipment or software, that captures images with horizontally elongated fields of view. It is sometimes known as wide format photography. The term has also been applied to a photograph that is cropped to a relatively wide aspect ratio, like the familiar letterbox format in wide-screen video.
A hole punch, also known as hole puncher, or paper puncher, is an office tool that is used to create holes in sheets of paper, often for the purpose of collecting the sheets in a binder or folder. A hole punch can also refer to similar tools for other materials, such as leather, cloth, or plastic or metal sheets.
Letter or ANSI Letter is a paper size standard defined by the American National Standards Institute, commonly used as home or office stationery in the United States, Canada, Chile, Colombia, Costa Rica, Mexico, Panama, Guatemala, the Dominican Republic and the Philippines. It measures 8.5 by 11 inches and is similar in use to the A4 paper standard at 210 mm × 297 mm used by most other countries, defined in ISO 216 by the International Organization for Standardization.
In digital photography, the crop factor, format factor, or focal length multiplier of an image sensor format is the ratio of the dimensions of a camera's imaging area compared to a reference format; most often, this term is applied to digital cameras, relative to 35 mm film format as a reference. In the case of digital cameras, the imaging device would be a digital image sensor. The most commonly used definition of crop factor is the ratio of a 35 mm frame's diagonal (43.3 mm) to the diagonal of the image sensor in question; that is, . Given the same 3:2 aspect ratio as 35mm's 36 mm × 24 mm area, this is equivalent to the ratio of heights or ratio of widths; the ratio of sensor areas is the square of the crop factor.
The size of a book is generally measured by the height against the width of a leaf, or sometimes the height and width of its cover. A series of terms is commonly used by libraries and publishers for the general sizes of modern books, ranging from folio, to quarto (smaller) and octavo. Historically, these terms referred to the format of the book, a technical term used by printers and bibliographers to indicate the size of a leaf in terms of the size of the original sheet. For example, a quarto historically was a book printed on sheets of paper folded in half twice, with the first fold at right angles to the second, to produce 4 leaves, each leaf one fourth the size of the original sheet printed – note that a leaf refers to the single piece of paper, whereas a page is one side of a leaf. Because the actual format of many modern books cannot be determined from examination of the books, bibliographers may not use these terms in scholarly descriptions.
The ISO 217:2013 standard defines the RA and SRA paper formats.
Anamorphic format is the cinematography technique of shooting a widescreen picture on standard 35 mm film or other visual recording media with a non-widescreen native aspect ratio. It also refers to the projection format in which a distorted image is "stretched" by an anamorphic projection lens to recreate the original aspect ratio on the viewing screen. The word anamorphic and its derivatives stem from the Greek anamorphoo, compound of morphé with the prefix aná. In the late 1990s and 2000s, anamorphic lost popularity in comparison to "flat" formats such as Super 35 with the advent of digital intermediates; however, in the years since digital cinema cameras and projectors have become commonplace, anamorphic has experienced a considerable resurgence of popularity, due in large part to the higher base ISO sensitivity of digital sensors, which facilitates shooting at smaller apertures.
In 1992, the American National Standards Institute adopted ANSI/ASME Y14.1Decimal Inch Drawing Sheet Size and Format, which defined a regular series of paper sizes based upon the de facto standard 8+1⁄2 in × 11 in "letter" size to which it assigned the designation "ANSI A". This series also includes "ledger"/"tabloid" as "ANSI B". This series is somewhat similar to the ISO 216 standard in that cutting a sheet in half would produce two sheets of the next smaller size. Unlike the ISO standard, however, the arbitrary aspect ratio forces this series to have two alternating aspect ratios. ANSI/ASME Y14.1 has been revised or updated in 1995, 2005, 2012 and 2022. It had an accompanying standard, ANSI/ASME Y14.1M, that defined metric drawing paper sizes based upon ISO 216 and ISO 5457. ASME Y14.1 and ASME Y14.1M have now been revised and consolidated into one document, ASME Y14.1-2020, Drawing Sheet Size and Format, published on 18 December 2020.
The aspect ratio of an image is the ratio of its width to its height, and is expressed with two numbers separated by a colon, such as 16:9, sixteen-to-nine. For the x:y aspect ratio, the image is x units wide and y units high. Common aspect ratios are 1.85:1 and 2.39:1 in cinematography, 4:3 and 16:9 in television photography, and 3:2 in still photography.
