Darkroom (photography)
A darkroom is a room that is absolutely light-tight, so that no light can penetrate from the outside, but can certainly allow (artificial) special lighting inside. In chemical photography, such a space serves as a sub-unit of the photo laboratory or photocopier .
Areas of application
Absolute darkness or restriction to light of a special spectral range is required to work where light-sensitive materials or photo emulsions are handled. Here light-sensitive black and white and color emulsions come into question, which can be on various carrier materials, e.g. B. on a thin film of polyester or cellulose , on glass , on somewhat thicker plastic sheets or on foil or fabrics and cardboard.
The darkroom in the photo lab
Many light-sensitive emulsions are only sensitive to certain types of light, ie to light of a certain wavelength . This has the advantage that you can safely use light to which the photo emulsion is not sensitive. See also: light spectrum and wavelength.
The darkroom is by no means permanently dark. Rather, the darkroom fulfills the task of using light in an absolutely controlled manner.
In the case of unintentionally uncontrolled light penetrating from the outside, one also speaks of “scattered light”, “incidence of light”, “ingress of light”, “light leak”.
Light locks and light labyrinths
To avoid light entering the darkroom, a light lock is used. A light lock basically consists of two doors. It can also be black, heavy curtains. If you now enter this lock from the outside, you close the first door behind you, so that you are now inside the lock in absolute darkness. Then you open the second door and you can enter the actual darkroom.
Light mazes for ventilation
If you have darkened a room (a so-called changing bag is sufficient for many purposes ), you have to ensure good ventilation at the same time, as the air in a tight room can quickly become stuffy. To do this, a light-tight fan can be built into windows and doors. A labyrinth is used for such purposes . It is understood as a system of multiple channels diverted at right angles, the insides of which are painted black. The angles help to avoid direct incidence of light. The black color prevents reflection of penetrating light into the darkroom. The darkroom is thus open to fresh air, but light cannot penetrate.
Light labyrinths in development boxes
Such labyrinths have also been found on a small scale since the 1950s, namely in film developing tanks . The labyrinths are used there to allow the chemical solutions necessary for film development to reach the photographic materials in a light-tight manner. Processing tanks are extremely popular in the area of 35mm and roll film processing. This reduces the duration of absolute darkness in the processing of the photosensitive material to the duration of the insertion of the material into the tank. The actual development can then take place in daylight .
Lighting in the darkroom
At the time of working with emulsion-coated glass plates (before the invention of 35mm film and roll film ), the recording material had to be developed in dishes. There were light-sensitive emulsions that were insensitive to red light. These emulsions are called orthochromatic (as opposed to panchromatic ). One could develop this recording material in red light and observe the development progress in statu nascendi .
This is where an essential purpose of the darkroom becomes apparent: Because today's photo papers, onto which a negative is enlarged, are also insensitive to certain types of light in the case of black and white processing, even beginners can observe and control the image impression resulting from chemical processing by using the open Shell is developed longer or shorter depending on the appearance, or by heating certain image areas separately while the development is in full swing, or by controlled external light, e.g. B. by switching on the main lighting, hits the image under development to create a so-called pseudo-solarization . See also: photographic effect .
Color film processing
When processing color films, which are mostly sensitized to all types of light ( wavelength ), many of these control options are no longer available . Here, even with large image formats, the tank development is used instead of using the bowls. After all, the result cannot be viewed so easily while it is being created. In addition, when working in absolute darkness and with liquids, which are mostly harmful to health, there is a risk of spilling them, which can contaminate other chemical baths as well as cause large and ugly, difficult-to-remove stains on clothing. Sensitive mechanical-electronic devices such as B. the enlarger (enlarger) or the dry press are at risk.
Digital darkroom
With the spread of digital photography , darkrooms are losing popularity. The post-processing of digital images on the computer is also known as a digital darkroom. The term includes both the devices used ( scanner , computer , photo printer ) and the software necessary for image processing or image processing , such as scan programs, RAW converters, image management and image manipulation software, and effect programs.
See also
literature
- Kisselbach, Theo: Darkroom manual . Seebruck: Heering-Verlag 1971.
- Langford, Michael: Darkroom manual Hallwag Verlag Bern and Stuttgart 1983
