Photographic Paper
   HOME

TheInfoList



OR:

Photographic paper is a paper coated with a light-sensitive chemical, used for making
photographic print Photographic printing is the process of producing a final image on paper for viewing, using chemically sensitized paper. The paper is exposed to a photographic negative, a positive transparency (or ''slide''), or a digital image file projected ...
s. When photographic paper is exposed to light, it captures a
latent image A latent image is an invisible image produced by the exposure to light of a photosensitive material such as photographic film. When photographic film is developed, the area that was exposed darkens and forms a visible image. In the early days of ...
that is then developed to form a visible image; with most papers the image density from exposure can be sufficient to not require further development, aside from fixing and clearing, though latent exposure is also usually present. The light-sensitive layer of the paper is called the
emulsion An emulsion is a mixture of two or more liquids that are normally Miscibility, immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloi ...
, and functions similarly to
photographic film Photographic film is a strip or sheet of transparent film base coated on one side with a gelatin photographic emulsion, emulsion containing microscopically small light-sensitive silver halide crystals. The sizes and other characteristics of the ...
. The most common chemistry used is gelatin silver, but other alternatives have also been used. The print image is traditionally produced by interposing a photographic negative between the light source and the paper, either by direct contact with a large negative (forming a
contact print A contact print is a photographic image produced from Photographic film, film; sometimes from a film negative (photography), negative, and sometimes from a film positive or paper negative. In a darkroom an exposed and developed piece of film or ...
) or by projecting the shadow of the negative onto the paper (producing an enlargement). The initial light exposure is carefully controlled to produce a
grayscale In digital photography, computer-generated imagery, and colorimetry, a greyscale (more common in Commonwealth English) or grayscale (more common in American English) image is one in which the value of each pixel is a single sample (signal), s ...
image on the paper with appropriate contrast and gradation. Photographic paper may also be exposed to light using digital printers such as the LightJet, with a camera (to produce a photographic negative), by scanning a modulated light source over the paper, or by placing objects upon it (to produce a
photogram A photogram is a Photography, photographic image made without a camera by placing objects directly onto the surface of a light-sensitive material such as photographic paper and then exposing it to light. The usual result is a negative shadow im ...
). Despite the introduction of digital photography, photographic papers are still sold commercially. Photographic papers are manufactured in numerous standard sizes, paper weights and
surface finish Surface finish, also known as surface texture or surface topography, is the nature of a interface (matter), surface as defined by the three characteristics of lay, surface roughness, and waviness.. It comprises the small, local deviations of a ...
es. A range of
emulsions An emulsion is a mixture of two or more liquids that are normally immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloids. Althoug ...
are also available that differ in their light sensitivity, colour response and the warmth of the final image. Color papers are also available for making colour images.


History

The effect of light in darkening a prepared paper was discovered by Thomas Wedgwood in 1802. Photographic papers have been used since the beginning of all negative–positive
photographic processes A list of photographic processing techniques. Color * Agfacolor ** Ap-41 process (pre-1978 Agfa color slides; 1978-1983 was a transition period when Agfa slowly changed their color slide films from AP-41 to E6) * Anthotype * Autochrome Lumière, ...
as developed and popularized by
William Fox Talbot William Henry Fox Talbot (; 11 February 180017 September 1877) was an English scientist, inventor, and photography pioneer who invented the salted paper and calotype processes, precursors to photographic processes of the later 19th and 20th ce ...
's 1841
calotype Calotype or talbotype is an early photographic process introduced in 1841 by William Henry Fox Talbot, using paper coated with silver iodide. Paper texture effects in calotype photography limit the ability of this early process to record low ...
. After the early days of photography, papers have been manufactured on a large scale with improved consistency and greater light sensitivity.


Types of photographic papers

Photographic papers fall into one of three sub-categories: * Papers used for negative-positive processes. This includes all current
black-and-white Black-and-white (B&W or B/W) images combine black and white to produce a range of achromatic brightnesses of grey. It is also known as greyscale in technical settings. Media The history of various visual media began with black and white, ...
papers and chromogenic colour papers. * Papers used for positive-positive processes in which the "film" is the same as the final image (e.g., the Polaroid process,
Imago In biology, the imago (Latin for "image") is the last stage an insect attains during its metamorphosis, its process of growth and development; it is also called the ''imaginal'' stage ("imaginal" being "imago" in adjective form), the stage in wh ...
direct positive paper). * Papers used for positive-positive film-to-paper processes where a positive image on a film slide is enlarged and copied onto a photographic paper, for example the Ilfochrome process.


Structure

All photographic papers consist of a light-sensitive
emulsion An emulsion is a mixture of two or more liquids that are normally Miscibility, immiscible (unmixable or unblendable) owing to liquid-liquid phase separation. Emulsions are part of a more general class of two-phase systems of matter called colloi ...
, consisting of
silver halide A silver halide (or silver salt) is one of the chemical compounds that can form between the Chemical element, element silver (Ag) and one of the halogens. In particular, bromine (Br), chlorine (Cl), iodine (I) and fluorine (F) may each combine wit ...
salts suspended in a
colloid A colloid is a mixture in which one substance consisting of microscopically dispersed insoluble particles is suspended throughout another substance. Some definitions specify that the particles must be dispersed in a liquid, while others exte ...
al material – usually
gelatin Gelatin or gelatine () is a translucent, colorless, flavorless food ingredient, commonly derived from collagen taken from animal body parts. It is brittle when dry and rubbery when moist. It may also be referred to as hydrolyzed collagen, coll ...
-coated onto a paper, resin coated paper or polyester support. In black-and-white papers, the emulsion is normally sensitised to
blue Blue is one of the three primary colours in the RYB color model, RYB colour model (traditional colour theory), as well as in the RGB color model, RGB (additive) colour model. It lies between Violet (color), violet and cyan on the optical spe ...
and
green Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 nm. In subtractive color systems, used in painting and color printing, it is created by a com ...
light, but is insensitive to wavelengths longer than 600 nm in order to facilitate handling under red or orange
safelight A safelight is a light source suitable for use in a photographic darkroom. It provides illumination only from parts of the visible spectrum to which the photographic material in use is nearly, or completely insensitive. Design A safelight usua ...
ing. In chromogenic colour papers, the emulsion layers are sensitive to
red Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–750 nanometres. It is a primary color in the RGB color model and a seconda ...
,
green Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 nm. In subtractive color systems, used in painting and color printing, it is created by a com ...
and
blue Blue is one of the three primary colours in the RYB color model, RYB colour model (traditional colour theory), as well as in the RGB color model, RGB (additive) colour model. It lies between Violet (color), violet and cyan on the optical spe ...
light, respectively producing
cyan Cyan () is the color between blue and green on the visible spectrum of light. It is evoked by light with a predominant wavelength between 500 and 520 nm, between the wavelengths of green and blue. In the subtractive color system, or CMYK c ...
,
magenta Magenta () is a purple-red color. On color wheels of the RGB color model, RGB (additive) and subtractive color, CMY (subtractive) color models, it is located precisely midway between blue and red. It is one of the four colors of ink used in colo ...
and
yellow Yellow is the color between green and orange on the spectrum of light. It is evoked by light with a dominant wavelength of roughly 575585 nm. It is a primary color in subtractive color systems, used in painting or color printing. In t ...
dye Juan de Guillebon, better known by his stage name DyE, is a French musician. He is known for the music video of the single "Fantasy Fantasy is a genre of speculative fiction that involves supernatural or Magic (supernatural), magical ele ...
during processing.


Base materials


Black-and-white papers

Modern
black-and-white Black-and-white (B&W or B/W) images combine black and white to produce a range of achromatic brightnesses of grey. It is also known as greyscale in technical settings. Media The history of various visual media began with black and white, ...
papers are coated on a small range of bases; baryta-coated paper, resin-coated paper or polyester. In the past, linen has been used as a base material.


Fiber-based papers (FB)

Fiber-based (FB or Baryta) photographic papers consist of a paper base coated with baryta.Salvaggio, ''Nanette L. Basic Photographic Materials and Processes.'' Taylor & Francis US, Oct 27, 2008. p. 362. Tints are sometimes added to the baryta to add subtle colour to the final print; however most modern papers use optical brighteners to extend the paper's tonal range. Most fiber-based papers include a clear hardened gelatin layer above the emulsion which protects it from physical damage, especially during processing. This is called a supercoating. Papers without a super coating are suitable for use with the bromoil process. Fiber-based papers are generally chosen as a medium for high-quality prints for exhibition, display and archiving purposes. These papers require careful processing and handling, especially when wet. However, they are easier to
tone Tone may refer to: Visual arts and color-related * Tone (color theory), a mix of tint and shade, in painting and color theory * Tone (color), the lightness or brightness (as well as darkness) of a color * Toning (coin), color change in coins * ...
, hand-colour and retouch than resin-coated equivalents.


Resin-coated papers (RC)

The paper base of resin-coated papers is sealed by two
polyethylene Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging (plastic bags, plastic films, geomembranes and containers including bott ...
layers, making it impenetrable to liquids. Since no chemicals or water are absorbed into the paper base, the time needed for processing, washing and drying durations are significantly reduced in comparison to fiber-based papers. Resin paper prints can be finished and dried within twenty to thirty minutes. Resin-coated papers have improved dimensional stability, and do not curl upon drying.


The baryta layer

The term ''baryta'' derives from the name of a common
barium sulfate Barium sulfate (or sulphate) is the inorganic compound with the chemical formula Ba SO4. It is a white crystalline solid that is odorless and insoluble in water. It occurs in nature as the mineral barite, which is the main commercial source of ...
-containing mineral,
barite Baryte, barite or barytes ( or ) is a mineral consisting of barium sulfate (Ba S O4). Baryte is generally white or colorless, and is the main source of the element barium. The ''baryte group'' consists of baryte, celestine (strontium sulfate), ...
. However, the substance used to coat photographic papers is usually not pure
barium sulfate Barium sulfate (or sulphate) is the inorganic compound with the chemical formula Ba SO4. It is a white crystalline solid that is odorless and insoluble in water. It occurs in nature as the mineral barite, which is the main commercial source of ...
, but a mixture of barium and
strontium Strontium is a chemical element; it has symbol Sr and atomic number 38. An alkaline earth metal, it is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is exposed to ...
sulfates. The ratio of strontium to barium differs among commercial photographic papers, so chemical analysis can be used to identify the maker of the paper used to make a print and sometimes when the paper was made. The baryta layer has two functions 1) to brighten the image and 2) to prevent chemicals adsorbed on the fibers from infiltrating the gelatin layer. The brightening occurs because barium sulfate is in the form of a fine precipitate that scatters light back through the silver image layer. In the early days of photography, before baryta layers were used, impurities from the paper fibers could gradually diffuse into the silver layer and cause an uneven loss of sensitivity (before development) or mottle (unevenly discolour) the silver image (after development).


Colour papers

All colour photographic materials available today are coated on either RC (resin coated) paper or on solid polyester. The photographic emulsion used for colour photographic materials consists of three colour emulsion layers (
cyan Cyan () is the color between blue and green on the visible spectrum of light. It is evoked by light with a predominant wavelength between 500 and 520 nm, between the wavelengths of green and blue. In the subtractive color system, or CMYK c ...
,
yellow Yellow is the color between green and orange on the spectrum of light. It is evoked by light with a dominant wavelength of roughly 575585 nm. It is a primary color in subtractive color systems, used in painting or color printing. In t ...
, and
magenta Magenta () is a purple-red color. On color wheels of the RGB color model, RGB (additive) and subtractive color, CMY (subtractive) color models, it is located precisely midway between blue and red. It is one of the four colors of ink used in colo ...
) along with other supporting layers. The colour layers are sensitised to their corresponding colours. Although it is commonly believed that the layers in negative papers are shielded against the intrusion of light of a different wavelength than the actual layer by colour filters which dissolve during processing, this is not so. The colour layers in negative papers are actually produced to have speeds which increase from cyan (red sensitive) to magenta (green sensitive) to yellow (blue sensitive), and thus when filtered during printing, the blue light is "normalized" so that there is no crosstalk. Therefore, the yellow (blue sensitive) layer is nearly ISO 100 while the cyan (red) layer is about ISO 25. After adding enough yellow filtration to make a neutral, the blue sensitivity of the slow cyan layer is "lost". In negative-positive print systems, the blue sensitive layer is on the bottom, and the cyan layer is on the top. This is the reverse of the usual layer order in colour films. The emulsion layers can include the colour dyes, as in Ilfochrome; or they can include colour couplers, which react with colour developers to produce colour dyes, as in type C prints or chromogenic negative–positive prints. Type R prints, which are no longer made, were positive–positive chromogenic prints.


Black and white emulsion types

The emulsion contains light sensitive
silver halide A silver halide (or silver salt) is one of the chemical compounds that can form between the Chemical element, element silver (Ag) and one of the halogens. In particular, bromine (Br), chlorine (Cl), iodine (I) and fluorine (F) may each combine wit ...
crystals suspended in gelatin. Black-and-white papers typically use relatively insensitive emulsions composed of agb
silver bromide Silver bromide (AgBr), a soft, pale-yellow, water-insoluble salt well known (along with other silver halides) for its unusual sensitivity to light. This property has allowed silver halides to become the basis of modern photographic materials. AgB ...
,
silver chloride Silver chloride is an inorganic chemical compound with the chemical formula Ag Cl. This white crystalline solid is well known for its low solubility in water and its sensitivity to light. Upon illumination or heating, silver chloride converts ...
or a combination of both. The silver halide used affects the paper's sensitivity and the image tone of the resulting print.


Chloride papers

Popular in the past, chloride papers are nowadays unusual; a single manufacturer produces this material. These insensitive papers are suitable for contact printing, and yield warm toned images by development. Chloride emulsions are also used for printing-out papers, or POP, which require no further development after exposure.


Chlorobromide papers

Containing a blend of silver chloride and silver bromide salts, these emulsions produce papers sensitive enough to be used for enlarging. They produce warm-black to neutral image tones by development, which can be varied by using different developers.


Bromide papers

Papers with pure silver bromide emulsions are sensitive and produce neutral black or 'cold' blue-black image tones.


Contrast control

''Fixed-grade'' – or ''graded'' – black-and-white papers were historically available in a range of 12 grades, numbered 0 to 5, with 0 being the ''softest'', or least contrasty paper grade and 5 being the ''hardest'', or most contrasty paper grade. Low contrast negatives can be corrected by printing on a contrasty paper; conversely a very contrasty negative can be printed on a low contrast paper. Because of decreased demand, most extreme paper grades are now discontinued, and the few graded ranges still available include only middle contrast grades. ''Variable-contrast'' – or "VC" – papers account for the great majority of consumption of these papers in the 21st century. VC papers permit the selection of a wide range of contrast grades, in the case of the brand leader between 00 and 5. These papers are coated with a mixture of two or three emulsions, all of equal contrast and sensitivity to
blue Blue is one of the three primary colours in the RYB color model, RYB colour model (traditional colour theory), as well as in the RGB color model, RGB (additive) colour model. It lies between Violet (color), violet and cyan on the optical spe ...
light. However, each emulsion is sensitised in different proportions to
green Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 nm. In subtractive color systems, used in painting and color printing, it is created by a com ...
light. Upon exposure to blue light, all emulsions act in an additive manner to produce a high contrast image. When exposed to green light alone, the emulsions produce a low contrast image because each is differently sensitised to green. By varying the ratio of blue to green light, the contrast of the print can be approximately continuously varied between these extremes, creating all contrast grades from 00 to 5. Filters in the enlarger's light path are a common method of achieving this control.
Magenta Magenta () is a purple-red color. On color wheels of the RGB color model, RGB (additive) and subtractive color, CMY (subtractive) color models, it is located precisely midway between blue and red. It is one of the four colors of ink used in colo ...
filters absorb green and transmit blue and red, while
yellow Yellow is the color between green and orange on the spectrum of light. It is evoked by light with a dominant wavelength of roughly 575585 nm. It is a primary color in subtractive color systems, used in painting or color printing. In t ...
filters absorb blue and transmit green and red. The contrast of photographic papers can also be controlled during processing or by the use of bleaches or toners.


Panchromatic papers

Panchromatic black-and-white photographic printing papers are sensitive to all wavelengths of visible light. They were designed for the printing of full-tone black-and-white images from colour negatives; this is not possible with conventional orthochromatic papers. Panchromatic papers can also be used to produce paper negatives in large-format cameras. These materials must be handled and developed in near-complete darkness. Kodak Panalure Select RC is an example of a panchromatic black-and-white paper; it was discontinued in 2005.


Non Silver papers

Numerous photo sensitive papers that do not use silver chemistry exist. Most are hand made by enthusiasts but
cyanotype The cyanotype (from , and , ) is a slow-reacting, photographic printing formulation sensitive to a limited near-ultraviolet and blue light spectrum, the range 300 nm to 400 nm known as UVA radiation. It produces a monochrome, blu ...
prints are made on what was commonly sold as
blueprint A blueprint is a reproduction of a technical drawing or engineering drawing using a contact print process on light-sensitive sheets introduced by Sir John Herschel in 1842. The process allowed rapid and accurate production of an unlimited number ...
paper. Certain precious metal including
platinum Platinum is a chemical element; it has Symbol (chemistry), symbol Pt and atomic number 78. It is a density, dense, malleable, ductility, ductile, highly unreactive, precious metal, precious, silverish-white transition metal. Its name origina ...
and other chemistries have also been in common use at certain periods.


Archival stability

The longevity of any photographic print media will depend upon the processing, display and storage conditions of the print.


Black-and-white prints

''Fixing'' must convert all non-image silver into soluble silver compounds that can be removed by washing with water. ''Washing'' must remove these compounds and all residual fixing chemicals from the emulsion and paper base. A hypo-clearing solution, also referred to as hypo clearing agent, HCA, or a washing aid, and which can consist of a 2% solution of
sodium sulfite Sodium sulfite (sodium sulphite) is the inorganic compound with the chemical formula Na2SO3. A white, water-soluble solid, it is used commercially as an antioxidant and preservative. It is also suitable for the softening of lignin in the pulping an ...
, can be used to shorten the effective washing time by displacing the thiosulfate fixer, and the byproducts of the process of fixation, that are bound to paper fibers.Kachel, David
Fixing, Washing & Toning Fine B&W Photographs: Processing Your Materials Correctly
''Toners'' are sometimes used to convert the metallic silver into more stable compounds. Commonly used archival toners are:
selenium Selenium is a chemical element; it has symbol (chemistry), symbol Se and atomic number 34. It has various physical appearances, including a brick-red powder, a vitreous black solid, and a grey metallic-looking form. It seldom occurs in this elem ...
,
gold Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...
and
sulfide Sulfide (also sulphide in British English) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to large families o ...
. Prints on fiber-based papers that have been properly fixed and washed should last at least fifty years without fading. Some alternative non-silver processes – such as
platinum prints Platinum prints, also called ''platinotypes'', are photographic prints made by a monochrome photographic printing, printing process involving platinum. Platinum tones range from warm black, to reddish brown, to expanded mid-tone grays that are ...
– employ metals that are, if processed correctly, inherently more stable than gelatin-silver prints.


Colour prints

For colour images, Ilfochrome is often used because of its clarity and the stability of the colour dyes.


See also

* Standard AD size * Film format#Still photography film formats *
Paper size Paper size refers to Technical standard, standardized dimensions for sheets of paper used globally in stationery, printing, and technical drawing. Most countries adhere to the ISO 216 standard, which includes the widely recognized A series ( ...
* Photo print sizes


References

{{Authority control Coated paper Photography equipment Photographic processes