Tabular-grain film
Encyclopedia
Tabular-grain film is a type of photographic film
that includes nearly all color films, T-MAX
films from Kodak (with Kodak's T-grain emulsion), Delta
films from Ilford Photo
and the Fujifilm
Neopan
films. The silver halide
crystal
s in the film emulsion
are flatter and more tabular (hence T-Grain).
emulsions, the sensitivity of the silver halide
crystal is enhanced by sensitizing dyes that adsorb on the crystal surface. Therefore, sensitivity can be increased by adsorbing more sensitizing dye. This requires increasing the surface area of the crystal, and also improving the dye molecules to form a dense assembly of the dye molecules. Tabular grain emulsion solves the first part of this problem.
Tabular crystals tend to lie along the film's surface when coated and dried. This reduces scattering of light and increases resolution.
Tabular crystals usually have two twinned planes parallel to each other. They are formed at the very beginning of the crystallization. The crystal tends to grow at the edges and not on the main planes, forming very thin crystals of very large surface areas. Tabular crystals probably existed from very early days of silver-gelatin photography. However, it was about 1970 when emulsion engineers could make emulsions that consisted mainly of tabular crystals. Moreover, it was not until the 1980's that tabular crystals began to be used in production emulsions.
Tabular grain technology brought significant improvements to the image quality of the film, particularly in the improvement of resolution and granularity. However, several more key technologies were implemented into tabular grain products. Many of these concurrent improvements were applied to non-tabular grain products to improve image quality. Therefore, when tabular grain technology is described by uninformed writers, its advantage tends to be overemphasized. For example, excellent reciprocity law
is not an inherent property of tabular crystals but rather the result of other techniques introduced at about the same time.
.
Photographic film
Photographic film is a sheet of plastic coated with an emulsion containing light-sensitive silver halide salts with variable crystal sizes that determine the sensitivity, contrast and resolution of the film...
that includes nearly all color films, T-MAX
Kodak T-MAX
Kodak Professional T-MAX Film is a continuous tone, panchromatic, tabular-grain black and white negative film made by Eastman Kodak. It is sold in three speeds: 100, 400 and 3200...
films from Kodak (with Kodak's T-grain emulsion), Delta
Ilford Delta
Ilford Delta is a series of photographic films manufactured by Harman Technology Limited. Delta films are tabular-grain black-and-white films....
films from Ilford Photo
Ilford Photo
Ilford Photo is a manufacturer of photographic materials known worldwide for its black-and-white film and papers and chemicals, as well as its range of Ilfochrome and Ilfocolor colour printing materials. Ilfochrome was formerly called Cibachrome, developed in partnership with the Swiss company...
and the Fujifilm
Fujifilm
is a multinational photography and imaging company headquartered in Tokyo, Japan.Fujifilm's principal activities are the development, production, sale and servicing of color photographic film, digital cameras, photofinishing equipment, color paper, photofinishing chemicals, medical imaging...
Neopan
Neopan
Neopan is a family of black-and-white films from Japanese manufacturer Fujifilm.-Neopan 100 Acros:Acros is a brandname for an ISO 100 speed orthopanchromatic black-and-white photographic film produced by the Japanese company Fujifilm. As of early 2011, the film is available in 135 and 120 formats...
films. The silver halide
Silver halide
A silver halide is one of the compounds formed between silver and one of the halogens — silver bromide , chloride , iodide , and three forms of silver fluorides. As a group, they are often referred to as the silver halides, and are often given the pseudo-chemical notation AgX...
crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...
s in the film emulsion
Photographic emulsion
Photographic emulsion is a light-sensitive colloid, such as gelatin, coated onto a substrate. In silver-gelatin photography, the emulsion consists of silver halide crystals suspended in gelatin, and the substrate may be glass, plastic film, paper or fabric....
are flatter and more tabular (hence T-Grain).
Tabular crystals
In panchromaticPanchromatic
Panchromatic film is a type of black-and-white photographic film that is sensitive to all wavelengths of visible light. A panchromatic film therefore produces a realistic reproduction of a scene as it appears to the human eye. Almost all modern photographic film is panchromatic, but some types are...
emulsions, the sensitivity of the silver halide
Silver halide
A silver halide is one of the compounds formed between silver and one of the halogens — silver bromide , chloride , iodide , and three forms of silver fluorides. As a group, they are often referred to as the silver halides, and are often given the pseudo-chemical notation AgX...
crystal is enhanced by sensitizing dyes that adsorb on the crystal surface. Therefore, sensitivity can be increased by adsorbing more sensitizing dye. This requires increasing the surface area of the crystal, and also improving the dye molecules to form a dense assembly of the dye molecules. Tabular grain emulsion solves the first part of this problem.
Tabular crystals tend to lie along the film's surface when coated and dried. This reduces scattering of light and increases resolution.
Tabular crystals usually have two twinned planes parallel to each other. They are formed at the very beginning of the crystallization. The crystal tends to grow at the edges and not on the main planes, forming very thin crystals of very large surface areas. Tabular crystals probably existed from very early days of silver-gelatin photography. However, it was about 1970 when emulsion engineers could make emulsions that consisted mainly of tabular crystals. Moreover, it was not until the 1980's that tabular crystals began to be used in production emulsions.
Tabular grain technology brought significant improvements to the image quality of the film, particularly in the improvement of resolution and granularity. However, several more key technologies were implemented into tabular grain products. Many of these concurrent improvements were applied to non-tabular grain products to improve image quality. Therefore, when tabular grain technology is described by uninformed writers, its advantage tends to be overemphasized. For example, excellent reciprocity law
Reciprocity (photography)
In photography reciprocity refers to the inverse relationship between the intensity and duration of light that determines the reaction of light-sensitive material. Within a normal exposure range for film stock, for example, the reciprocity law states that the film response will be determined by the...
is not an inherent property of tabular crystals but rather the result of other techniques introduced at about the same time.
Fixing tabular crystals
Tabular crystals grow along the edges and not on the main planes. Similarly, tabular crystals dissolve mainly along the edges and this causes the crystals more difficult and slow to fix in the fixing stage. Users of tabular grain films are advised to ensure sufficient fixing time, at least twice the clearing time in rapid fixerPhotographic fixer
Photographic fixer is a chemical or a mix of chemicals used in the final step in the photographic processing of film or paper. The fixer stabilises the image, removing the unexposed silver halide remaining on the photographic film or photographic paper, leaving behind the reduced metallic silver...
.