Darkroom glossary


Albumen print

A photograph printed on a paper base coated with egg white and sensitized with silver salts. The word albumen refers to the protein contained in egg white. Introduced in 1850, the invention became the most popular printing method of the 19th century. The paper base of an albumen print is thin, and therefore it is almost invariably mounted on a standard-sized cardboard backing board with decorations.

Analogue photography

The term analogue photography only came about in the age of digital photography and image processing, with the need to find an expression to refer to the traditional photographic methods of the film age. The term usually refers to photography that uses chemical methods to develop film exposed in an “analogue”, that is, a film camera, but it may also refer to all the photographic techniques that predate the digital age.


Atuloiksi kutsutaan valokuvien vedostuksessa käytettäviä pihtejä, joilla märkää valokuvavedosta siirretään kehitysnestealtaasta keskeytenesteeseen ja siitä edelleen kiinnitealtaaseen ja lopulta huuhtelutankkiin tai -altaaseen. Jokaista liuosta varten tarvitaan omat atulat. Atuloiden ansiosta vedokseen ei tarvitse tarttua käsin, joten vedostajan iho ei joudu suoraan kosketukseen haitallisten kemikaalien kanssa. Näin vältytään myös käsien epäpuhtauksien joutumiselta nesteisiin ja sormenjäljiltä vedoksissa. Atulat on yleensä valmistettu muovista tai metallista, ja niiden tarttumapinnat on pehmustettu kumilla.

The bromoil process

An early printing method that was popular particularly in the early decades of the 20th century. A Bromoil print is made by first printing the image on silver bromide paper. Next, the paper is bleached, and an oil-based ink is applied to the surface of the wet print using a squeegee or a brush. Often, the print is then transferred from the original paper to watercolor or lithographic paper, in which case the result is a Bromoil transfer print. The result is a painterly, soft-lined print that the printer can further enhance creatively using a brush.

Camera obscura

Camera obscura is based on an optical phenomenon in which light travels through a small aperture, gap or hole in a box or room, and forms an image on the wall opposite the hole. In the 16th century, the camera obscura was a device used to help with the drawing of perspective, being a mobile room with light coming through a hole in the front wall, forming an inverted image on the back wall. In the 17th century, the camera obscura was reduced to a small box, which was further developed by placing a glass lens in the pinhole, resulting in improved image quality. A mirror was placed inside the box that projected the image onto the focusing screen at the top. The same principle is in use, for example, in many of today’s cameras, whether disposable, system or digital.

Carbon print

A print in which the image is created using carbon pigment. A carbon print is made by exposing the image onto paper through a negative, with light hardening the pigment gelatin containing chrome salts. The non-exposed areas are rinsed off in the final wash, and the carbon black pigment of the hardened areas forms the image. The carbon process requires special skill from the printer, and it fell out of use in the 1910s. However, it has, from time to time, interested photographic artists of later times.

Chromogenic colour print

The most common printed colour photographs are chromogenic colour prints. The chromogenic colour process is what is known as a subtractive colour process. The base of a colour print is a paper that has three surface layers of silver salts that are sensitive to different wavelengths of light. Each layer is sensitive to just one of the three primary colours: blue, green or red. The colours appear during the development process. At the end of the process, all the silver is removed from the print. Chromogenic colour paper is commonly used to print colour negatives.

Contact print

A print the size of a negative that has been exposed through the negative, directly onto paper. During printing, the surfaces of the negative and the photographic paper are in contact. In the 19th century and the early 20th century, photographs were typically contact prints, created using a printing frame. With small frame 35-mm film, contact prints are too small for most applications, so larger prints are usually created using an enlarger. Of course, you can create contact prints from 35-mm film, for example, for the preliminary selection of images to enlarge.

Collodion print

A silver image that has been printed on collodion emulsion paper. The collodion process was one of the popular printing methods of the late 19th century. Collodion papers are printing-out papers, that is, they are exposed in daylight and in contact with a negative, and no developer is required. Finally, all the unexposed silver is removed from the paper using a fixer.

Contact print

A print the size of a negative that has been exposed through the negative, directly onto paper. During printing, the surfaces of the negative and the photographic paper are in contact. In the 19th century and the early 20th century, photographs were typically contact prints, created using a printing frame. With small frame 35-mm film, contact prints are too small for most applications, so larger prints are usually created using an enlarger. Of course, you can create contact prints from 35-mm film, for example, for the preliminary selection of images to enlarge.

Contact printer

A device that professional users, such as photographic studios, use to create quick contact prints. This is an electric, box-like device that produces contact prints from negatives onto paper.


Photographic prints are also called copies. See printing-out print.


Also known as a blueprint, this is a photograph printed on paper that has been sensitised with blue-coloured iron salts. Paper sensitised in this way reacts to ultraviolet light, that is, daylight, so you do not need a darkroom to print it. Cyanotypes were made as early as in the second half of the 19th century, but the same process is still used today by some artists and photography enthusiasts.


The first publicly announced photographic process (1839), which was developed by the Frenchmen Joseph Louis Jacques Mandé Daguerre (1787–1851) and Nicéphore Niépce (1765–1833). A sheet of silver-plated copper is polished and fumed with iodine, producing a light-sensitive surface coating of silver iodide. The plate is exposed in the camera and then developed in mercury vapour: the mercury condenses on the exposed areas of the silver iodine surface, which means that the resulting image is formed from small drops of silver and mercury. The image is fixed in a sodium thiosulfate solution, washed in water, and toned with a gold chloride solution. The resulting daguerrotype has a mirror-like surface. When the light hits it at the right angle, at about 45 degrees, the negative image comes out as a positive.


Also known as a photographic laboratory, this is a darkened space in which you can process film or photographic paper so that it is not inadvertently exposed. Darkness is essential in the development of film and the printing of photographs. A darkroom can be a purpose-built space for photographic processing or a temporary unit set up in a barn, sauna, kitchen, bathroom or other domestic space. Darkrooms have been built since the late 19th century.

Darkroom clock

An exposure clock is used to adjust the required exposure time for a photographic print in the enlarger. Another clock can be used for timing the developing process.

Darkroom lamp/red light

In most cases, darkrooms feature a red working light, also known as a safelight, as black-and-white photographic paper is not sensitive to the wavelengths of red or reddish brown light. Other papers can also tolerate yellow or green light without being exposed. The earliest darkroom lamps included a candle or a gas light with a red glass cover around it.


A chemical used in photographic processes to develop out the latent image that is produced on film, photographic paper or another light-sensitive surface during exposure. In the development of black-and-white photographs, light-sensitive silver salt crystals reduce to metallic silver, which is no longer light-sensitive. There are different developers for each film and printing paper. Different types of developers are used to bring out different characteristics in a print, such as acutance or grain.

Developing tray

After exposure, a photographic print must be immersed in at least three solutions, in three different trays: the developer, stop bath, and fixer. The trays used today are typically shallow and made of plastic. They are agitated gently, so that the solution covers the image evenly.


Diapositive film, or reversal film, is a film type that produces a positive image on a transparent clear film. The developed film frames can be put in slide frames for viewing as slides, or transparencies, on a slide projector, projecting them onto a screen. Slides were very popular from the 1960s to the digital age. Diafilm is manufactured in 35-mm format, as roll film of different sizes, and as 8 × 10-inch sheet film, although with digital photography, the range is becoming narrower. Diafilm broke through especially in colour photography, although some black-and-white reversal films were manufactured, as well. Unlike black-and-white or colour negatives, a colour transparency is an original, and its reproduction is expensive and difficult. In practice, only so many copies of a high-quality colour transparency exist as there were successfully exposed frames at the time of taking the photographs.

Dye-diffusion print

Diffusion printing papers (or films) exploit the ability of silver to diffuse into a special receiving layer, the image layer, during the development process. On dye-diffusion paper, the image-forming dyes and silver remain invisible. The image layer of dye-diffusion prints is typically a fixed part of the exposed paper, while in dye-diffusion transfer prints, the dyes are transferred onto a separate image base. Dye-diffusion prints are often called Polaroids, after their most famous manufacturer.


For exposure, the photographic paper is placed on an easel on the enlarger base, to keep the paper flat and steady during exposure. The easel is also used to adjust the size of the area to be exposed on the paper.


An optical device that is used to enlarge a negative or positive image captured on transparent material, and then projected onto light-sensitive material, typically paper or film. In its simplest form, an enlarger includes a light source, a film carrier, and a lens. Typically, the enlarger structure includes a vertical bar. The light source is a lamp, from which light travels through the film in the carrier and the objective below it. The size of the image can be adjusted by raising and lowering the objective, and the image is focused on the enlarger base by adjusting the objective.

Exposure time

A period during which light reaches an image sensor, film, or photographic paper. The exposure time affects the darkness of the resulting image. Exposure time, then, is related to both photography and photographic printing. When photographing, a longer exposure time makes the image lighter: if the exposure time is long and the image is overexposed, areas in the image “burn out”, that is, show as all white. With the enlarger in the darkroom, the length of exposure has the opposite effect: if you expose the image for too long, it turns black.


When printing a photograph, different parts can be highlighted or hidden. The more light the film or printing paper receives, the darker the result. The exposure is often adjusted by hand or by “feathering”, using a “whisk” made of wire and a piece of paper or cardboard. See mask.


A photographic process that became common starting from the 1850s and remained popular until the 1930s. The base material of a ferrotype is a thin sheet of metal coated with a black or reddish-brown lacquer. The sensitized sheet of metal is exposed in the camera – this is the moment when the photograph is taken – and then it is quickly developed, rinsed, and dried. The ferrotype image looks positive against its dark background, although it is actually a negative. As it is not transparent, it cannot be used for printing, and so each ferrotype is a one-off. In America, the ferrotype is referred to as the ‘tintype’


Film is light-sensitive plastic that is used as a base for photographs and motion pictures. One side of black-and-white film is coated with a lightsensitive emulsion, consisting of silver salts and a binder. The size and other characteristics of the silver salt crystals influence the sensitivity, contrast and resolution of the film. Colour film has at least three lightsensitive layers. Each of these layers is sensitive to light of a specific colour: blue, green or red. Together, these three layers produce all the colours perceived by the eye. Film can be either negative or positive, as diafilm. Films are manufactured in different sizes and from a variety of materials.

Film developing spiral

For the duration of development, film is loaded onto a spiral. The spiral holds the roll of film in place while the developing tank is being agitated during the process of development. This enables the developing, stopping and fixing solutions to evenly reach all of the film. The spirals are manufactured from plastic and metal, and each film size has its own.

Film developing tank

Modern films are sensitive to all the wavelengths of light, and therefore they must be developed in complete darkness, in a lightproof developing tank. The roll or pack film loaded onto the developing spiral is placed in the tank in a dark room. Once the lid of the tank is closed tightly, the processing can continue in daylight, because the structure of the tank prevents the film from being exposed. The first step in the film development process is to pour water into the tank to make the film wet. You then pour liquids into and out of the developing tank: developer, stop bath and fixer. Finally, the film is removed from the tank, rinsed and dried. Film developing tanks come in different sizes; some can hold one developing spiral, while others can hold several spirals of different sizes. The tanks are typically made of metal or black plastic.


When printing black-and-white photographs in the darkroom, a red filter is placed in front of the enlarger lens, to prevent the paper from being exposed while it is being put in place and the image is being focused. In creating colour prints, again, the colour filters placed in the enlarger are used to adjust the final tones of the image.


Once the film or print has been developed, it still contains some light sensitive material that must be removed in order for the image to remain intact when exposed to light. Different fixing chemicals are used for this purpose, most commonly sodium thiosulfate.

Focus finder

A loupe-like instrument used in the darkroom to check the definition of an image projected onto paper from an enlarger. With the focus finder, you can discern details in an image at the level of silver grains.

Gum printing or gum-bichromate process

Gum printing is a non-silver photographic process based on the use of chromium salts. A mixture of gum arabic, pigments and bichromate is applied to the printing paper. The dried paper is exposed to ultraviolet light as a contact copy, which hardens the gum arabic. Next, the image is rinsed to wash off the unexposed mixture. The print often requires several exposures, and it needs to be sensitized again after each exposure. Finally, it is rinsed, washed and dried. This multi-step process requires precision and skill. Gum printing was very popular among the Pictorialists, and in Finland particularly in the 1920s.

Latent image

An invisible image. When a photograph is taken, light travels through the lens of the camera onto film, which has a coating that contains silver salts that react chemically to light. A latent, “invisible” image forms on the surface of the film. In the same way, when a photographic print is being made in the darkroom, the image is exposed on light-sensitive photographic paper, where it is first formed latent. The latent image is made visible by developing the film or print.


A workspace equipped for film and photograph development is often referred to as a photographic laboratory. See darkroom.

Lith film

Film with lower light sensitivity, often orthochromatic, also known as slow film, designed for printing applications. Lith film has been used in photographic art especially for creating photographics works. It is useful in maximising the solarisation effect.


A self-made printing aid used to adjust the relative darkness of details in an image. The darkness of a photographic print depends on the amount of light it receives at the time when the photograph is taken, and the amount of light the photographic paper receives in the enlarger. It is often the case that even when you find the best exposure time for the image as a whole, certain details still remain too light or too dark. If this happens, you can correct the exposure in the darkroom using a special “mask” or “whisk”. A mask can be a piece of cardboard or a photographic print that has been cut into a suitable shape, which is moved over the photographic paper, so that that particular area receives less exposure from the enlarger. Alternatively, the mask can cover the entire image field apart from a hole that only allows light to reach a desired area. For smaller details, you can make a small “whisk”, which is basically a piece of paper that has an arm made of wire so you can move it. Instead of using a mask, photographers have adjusted exposure in the darkroom by shading with a hand or even by blowing cigarette smoke over the photographic paper at the right moment. See feather/whisk.


When photographing with a film camera, the image is captured on a transparent base as a negative, which is then used to create a photographic print in the darkroom. The tonal range of a negative is the reverse of the photographed subject: for example, light sky comes out dark in the negative and vice versa. Correspondingly in a colour negative, green grass comes out as red, but when the image is printed on colour photographic paper, the colours are reversed again to appear “right”. You can use a negative to make unlimited copies, that is, photographic prints. Many of the first photographs (for example, daguerrotypes or ferrotypes) did not use transparent negatives, so they could not be copied. The material of the earliest printable negatives was thin, light-sensitised paper. Later, glass, and eventually different types of plastic, negatives were used. Negatives are not needed in a digital camera, but instead, the image is stored on a memory card as a positive.

Non-silver printing processes

Photographic printing processes that were invented in the early days of photography, but that have since become rare, with images created using materials other than silver. Non-silver printing processes are used to produce, for example, Bromoil, gum-bichromate and carbon prints. Non-silver printing processes, also referred to as pigment processes, are distinguished from silver-based processes in that they are not based on the light sensitivity of silver. The main inspiration behind the development of these historic printing processes was the need to find more stable methods to create photographs than the silver-based processes, but there were also aesthetic reasons. These processes are often laborious and challenging, but they were a perfect match with the artistic objectives of the late-19th-century Pictorialists.

Orthochromatic film

Black-and-white film that is sensitive to blue and green. The earliest negatives were sensitive mainly to the blue wavelength of light. The orthochromatic films developed in the 1870s were the first improvement: they were now also sensitized to green, but not yet to the red and orange wavelengths of light. Consequently, reddish areas in the images were reproduced as black, and the blue areas often came out too light. In order for all areas of an image to be evenly exposed, red and yellow filters were required, or red dye was added to the negatives. This problem was resolved with the introduction of panchromatic film, which gradually replaced orthochromatic film. Today, orthochromatic film is used especially as a means of artistic expression.

Palladium/platinum print

A non-silver photographic print that uses platinum, or the less expensive palladium, as the image material. Paper sensitized with iron and platinum, or palladium salts is exposed in daylight and in contact with a negative. A developer is not necessarily needed, but it is often used in order to achieve a starker image. The unexposed iron salts are removed using a fixer (hydrochloric acid). The process was favoured by the Pictorialists because of the soft prints it produces.

Panchromatic film

Panchromatic black-and-white film is sensitive to all wavelengths of visible light. For this reason, it produces a more realistic reproduction of the tones of the photographed subject than the previously used orthochromatic films. Panchromatic materials were introduced in the mid-1930s, but they did not become popular until after the wars. These materials gained popularity slowly because they were expensive and their development required complete darkness. The development of panchromatic film requires sealable, light-tight film-developing tanks.


Resembling fine art prints but created in the darkroom through exposure, photographics prints often required a laborious process in many phases. First, you use the black-and-white negative and create a positive on lith film. This is then copied and made into a hard negative, which can be further retouched and processed as desired. A photographer constructs a photographics work in the darkroom, often combining several negatives and different techniques.


Photogram is a general term for photographs created without a camera or a lens. When creating a photogram, you first place, for example, an object directly onto the surface of a light-sensitive material, and then expose and process the material in the same way as a normal photograph. In a photogram, the object appears light against a dark background, or dark against a light background, because the material has not been exposed in the areas covered by the object. If the object is transparent or semi-transparent, the resulting photogram will also include tones between light and dark.

Photographic/printing paper

Photographs are printed on light-sensitive paper. Because of its sensitivity, the paper must be kept in a light-tight package until the time of use, so as to prevent it from darkening. In the early days of photography, printers sensitized the paper themselves, just before printing, and bought the required chemicals at a pharmacy. The earliest photographic papers were printing-out papers exposed with daylight. The early 20th century saw the introduction of photographic papers to be developed in artificial light (gas light). Later, these were replaced by silver bromide and gelatin silver papers. Plastic-coated paper gained popularity in the 1960s, but still, the most stable result is achieved using fibre-based paper. Colour-sensitive paper is required for colour printing. In black-and-white prints, too, the differences in the tone and surface of the paper influence the end result.

Pigment print

A print in which the image is formed by pigments. Currently, the term is commonly used to refer to inkjet prints that use the printer’s pigment inks. A ‘pigment print’, however, was in use in earlier times as a term for a photographic process that was popular in the 19th century but is currently rare. The original pigment prints were made using a non-silver process that uses a paper negative as its base. If carbon black is used as the pigment, we are dealing with a subtype of a pigment print, called a carbon print.

Pinhole camera

A simple camera that works on the camera obscura principle, which is basically a lightproof box. At one end of the box, you have light-sensitive film, unexposed photographic paper, and at the other end, you have a lens, or a hole created with a pin that projects an image upside down onto the back wall of the box. When you want to stop the exposure, you cover the hole, for example, with tape. You can make a pinhole camera yourself from an old film canister, cardboard box or, say, a sauna with covered windows.


The opposite of a negative: an image with a tonal range that matches that of the photographed subject. An ordinary photograph is a positive that has been printed from a negative. Transparencies are also positives.


Creation of a photograph on photographic paper. The main steps in the printing process are paper exposure, developing, halting, fixing, and finally washing. A print can also be toned. Finally, the print is dried using a dryer or left to dry in a ventilated space.

Printing frame

Printing frames were used starting from the 19th century, up until the early 20th century, for contact-printing paper photographs. Printing papers of that time were only sensitive to ultraviolet (UV) rays, that is, daylight. Examples of these are salt, albumen, collodion, and gelatin papers, and different types of printing papers for non-silver photographic processes. In the dark, a negative was placed in the frame against a glass plate, and a printing paper that is sensitive to ultraviolet light was placed under it. At the back of the frame was a two-part hinged wooden plate that pressed the printing paper and the negative tightly against each other using a spring mechanism. The frame was taken into daylight to expose the paper, and the image appeared during exposure. You could monitor the progress of the exposure by taking the frame out of the daylight, and by opening one side of the wooden back plate and peeking in to see the relative darkness of the printing paper. Once the print had become dark enough, the paper was removed and placed in a fixing solution, and then washed and dried. Printing frames are still used today when prints are created on the papers mentioned above.

Printing-out print

A contact print that is made without the use of an enlarger and exposed in daylight. In the printing-out paper, the image appears already during exposure. Finally, the image is fixed and the unexposed silver is removed from the paper using a fixer.

Print tongs

An instrument used in photographic printing to transfer a wet photographic print from the developing bath to the stop bath, and then to the fixing bath, and finally to the rinsing tank. Each bath should have their own tongs. With the tongs, you do not need to grab the print with your hands, so your skin does not come into direct contact with the harmful chemicals. In this way, you also avoid getting impurities from the hands in the liquids and getting fingermarks on your prints. The tongs are typically made from plastic or metal, and the gripping surfaces are padded with rubber.


A chemical used to reduce the density of a silver gelatin negative or positive. With a reducer, you can lighten an opaque film after the development process, by changing its metallic silver to easily soluble compounds that can then be rinsed off. A reducer can also be used to repair prints that appear too dark.


A chemical used to replace the chemicals that have been exhausted in the various developing baths. This means that you do not have to completely replace the developer, but its strength can be kept constant using a replenisher.

Sabatier effect

Pseudo-solarisation, see solarisation.

Salted paper process

One of the earliest photographic processes, dating from the 1830s. Fibre-based paper that has been sensitized with a salt solution and silver nitrate can be used either as a negative or as printing paper. The print is exposed in daylight and in contact with a negative. The resulting image is a contact print. Salted paper is printing-out paper, which means that there is no need for a developer in the printing process. At the end, all the unexposed silver is removed from the paper using a fixing solution and the image is rinsed. The salted-paper negative, however, needs to be developed. In the middle of the 19th century, the ability to produce copies was a definite advantage of the salted paper process, compared to earlier processes: one negative could be used to print many positive images.

Silver-dye-bleach print

Silver-dye-bleach paper has three layers of silver salts, each of which has been sensitised to one of the three primary colours: blue, green or red. Dye-bleach printing is a “reversal process”, whereby a colour transparency is developed into a colour print. The dyes are contained in the photographic paper, which finally undergoes a chemical process to remove all the silver and the extra dyes.

Silver gelatin print

Black-and-white photographs are usually gelatin silver prints. The print is exposed on photographic paper, which has silver salts mixed with gelatin in its light-sensitive emulsion. In development and fixing, the exposed silver salts are converted into metallic silver, and the unexposed silver is removed from the print using a fixer. Silver gelatin emulsions have been used in both printing-out and developing papers. Today, plastic paper is commonly used alongside the traditional fibre-based or baryta paper.


A graphical stylistic device in photographic printing in which the tones of an image are reversed. Actual solarisation occurs when the film is overexposed up to a thousand times, and, as a result, the dark areas in an image begin to turn light. However, in most cases ‘solarisation’ refers to the Sabattier effect, or pseudo-solarisation, in which a print or negative is exposed to extra light while immersed in the developer. This may also happen if standard white light is accidentally used in the darkroom during development. If you maximise the effect, the result is an image that only shows the contours of the photographed subjects. This requires lith film or film with high contrast, and several interim stages during which the tones of the image are reduced and made sharper.


A tool with a rubber blade, used to remove excess moisture from prints after they have been washed.

Stop bath

A stop bath is used in the processing of film or photographs and takes place between development and fixing. The stop bath immediately halts the development of the film. If the stop bath is not used, the development of the film will continue until the developer has been rinsed off the film and out of the developing tank. Using a stop bath, it is easier to reach exactly the desired development time. You can use diluted acetic acid, citric acid or plain water as a stop bath.


Bathing a print in a solution that changes its tone. Many toners (such as sulphide, selenium, and gold-based solutions) increase the longevity of the image, but they are also used as a stylistic device. Toning usually takes place at the end of the printing process. It is possible to use many toners for a single image at the same time.

Van dyke brown

A brown-toned contact print, exposed in daylight and made on paper sensitized with iron salts (ferric ammonium citrate) and silver, or on another surface as a printing-out print.

Wet plate

A photograph that is exposed and developed while the emulsion coating is still moist. A wet plate process using a collodion emulsion was introduced by the Englishman Frederick Scott Archer in 1851. The process involves coating and sensitising a glass plate with a light-sensitive silver emulsion just before use. The negative must be exposed and developed immediately before the emulsion dries. Ferrotypes, which are directly exposed on a metal plate, are also made using a wet plate process. Dry plates replaced the inconvenient wet plate processes starting from the 1870s.



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