The Darkroom
« Not explaining science seems to me perverse. When you're in love, you want to tell the world. »
- Carl Sagan (American Scientist 1934-1996)
Cypress Ridge High School darkroom, accessed while substitute teaching
« Do not lose sight of the essential importance of craft; every worthwhile human endeavor depends on the highest levels of concentration and mastery of basic tools. »
-Ansel Adams (American Photographer 1902-1984)
The Enlarger
Super Chromega D Dichroic II enlarger with Chromegatrol power supply (ca.1980s)
This enlarger is capable of printing up to 4x5 inch film, and as small as 35mm. It is capable of making prints larger than 40x40 inches
The Film Developer
Rodinal (film developer)
4-amenophenol and potassium hydroxide are the main ingredients in this century+ old german formula. These chemicals act to catalyze the generation of elemental silver in a film emulsion around the latent silver particles formed during exposure in camera. Rodinal is currently the oldest photographic chemical developer still in production, having been created in 1892 (it is likely the oldest photographic material in continuous production).
(concentrations of 1+25 - 1+50 are generally used)
The Paper Developer
Ilford Multigrade (paper developer)
Sodium Sulphite and Potassium Carbonate form the primary ingredients in this developer from the British photographic company Ilford. This chemical acts to catalyze the generation of elemental silver in a paper emulsion around the latent silver particles formed during exposure under the photographic enlarger.
(concentrations of 1+9 or 1+14 can be used)
The Photographic Fixer
Ilford Rapid Fixer
Ammonium thiosulphate is the active ingredient in many modern day photo fixers. This chemical washes the light sensitive silver salts from a film or final print, keeping them from darkening upon further exposure to light.
(concentrations of 1+4 or 1+9 can be used)
Ilford Photographic materials
A staple of my darkroom, and darkrooms the world over.
Since the marked decline of the film industry, following the development of digital cameras, and the all but dissolution of Kodak after the turn of the millenium, British photographic materials producer Ilford has risen to the forefront and now holds an 80% market share in black and white materials distributed globally.
Since the marked decline of the film industry, following the development of digital cameras, and the all but dissolution of Kodak after the turn of the millenium, British photographic materials producer Ilford has risen to the forefront and now holds an 80% market share in black and white materials distributed globally.
Film Stocks & Paper
Kodak
B/W
Tmax 3200, 400, 100
Color
Portra 400, 800
Ektar 100
Ilford
HP5+ & FP4+ Ilford Multigrade IV (Pearl)
Delta 100 & 400
Ortho 80
Pan F 50
SFX 200
Foma Bohemia
Foma 100
Foma 200
Foma 400
Scanning.Electron.Microscope imagery of silver halide crystals within an emulsion.
Units are in micrometers.
Worlds first photograph of a person,
By: Louis Daguerre, Paris
How it Works
This section will very briefly explain the subatomic properties and mechanism by which photography works, the same chemical reactions that allow us to take photos on film today and have for nearly 2 centuries now.
Key Terms:
Aperture:
Camera Obscura:
A dark box, or room, with a hole in one side through which light is allowed to project onto the opposing side of the interior, forming an image.
Developer:
Chemical agent used in the process of photo development, acts as a catalyst in the chemical reaction that brings a visible image out of the latent image formed during exposure in camera. In other words, these chemicals cause the crystalization of billions of atoms of silver around the invisible image centers formed in the emulsion when the film was exposed while capturing photographs, the silver crystals form the basis for what we see in a black and white photograph.
Note: More about physics and photochemistry can be found in sections below, research documents describing the science in detail can be found in the "Research" tab.
Emulsion:
The gelatine base (produced from cow bones) that modern photographic materials are coated with. This gelatin has in it an emulsion of very fine silver salt crystals, forming the light sensitive chemical agent within the emulsion.
Film:
A thin transparent plastic, cut into rolls or sheets, made light sensitive with the addition of a photographic emulsion to one or both sides.
Latent Image:
The invisible image formed in a photographic material upon exposure to light in a camera (or in the case of photo paper, from a photographic enlarger). This image consists of many thousands of Silver atoms separated from a halogen (Iodine, Chlorine, Bromine) by the action of light.
Lens:
A (generally compound) glass element used in directing light into a camera at varrying levels of optical zoom.
Lippmann Plate:
Used to capture the first full color photographs in a single photograph.
Photon:
Identified by Albert Einstein as individual packets of energy, this energy is seen to travel through space as either a particle or a wave.
Photo Paper:
Paper coated or soaked with a light sensetive material, typically halides of silver
Pinhole Camera:
Chemistry:
Collodion:
Fixer:
Ammonium Thiosulfate; used to remove the residual light sensetive silver salts following the full development and washing of a photographic material. Silver salts are soluble in Thiosulfates, and are thus washed out of a material when bathed during processing.
NOTE: Prolonged fixation will result in the bleaching of silver and will reduce the overall density and sharpness of a final negative or print.
Sensitizeing Dye:
Chemical dyes used to increase the sensetivity of a film. These dyes can either increase the overall sensitivity of an emulsion, by requiring fewer photons to generate an acceptable image, or can increase the spectral range over which a film will be photosensitive.
NOTE: All panchromatic photographic emulsions require sensitization to light other than blue. This is done with the addition of dyes that increase the red sensitivity of a layer, and dyes that increase the green sensitivity of another layer.
Silver Halide:
The key chemical responsible for the light sensitivity of the most successful and widely used photographic processes.
(Many other metal salts have been found to have light sensitive properties such as Platinum, Gold, Iron, and even Uranium. However, the sensitivity of silver salts are the only viably fast acting reactions found with currently avaliable photochemical knowledge and research.)
Note: More about physics and photochemistry can be found in sections below, research documents describing the science in detail can be found in the "Research" tab.
Stop Bath:
Stops the chemical reaction of the developer and the film, this is done to quickly halt the development and formation of silver crystals in a photograph once the desired density has been reached.
Note: Typically very acidic agents are used in stop baths, however, these prove to have detrimental effects on the long term archivability of photographic materials (which are better kept at neutral pH) and as such should be avoided. Rinses of 30 seconds are typical of acidic stop baths, but a bath in tap or distilled water of only twice the length of time will suffice to clear the developer to a similar extent.
How Does a Camera Obscura Work:
Optics: First described by scientists in china during the first millenia BC, the optical properties of cameras differ very little from our own eyes. As light enters through a pinhole it is directed to the opposing corner of a scene, when imagined as a projection by the viewer. This property of light results in an image that is both upside down and backwards in camera. This same thing is true in our own vision, a thing our brains automatically correct for.
Silver Halide Physics
(Film & Paper):
Exposure:
To very briefly summarize this process, when a photon hits a crystal of silver halide the energy added to the halide is sufficient to dislodge an electron from the orbital of one of the component elements, the resultant unbalanced force of which splits the molecule into metallic silver and halogen gas (Chlorine, Bromine, or Iodine). This halogen dissipates into the emulsion and the residual silver halide crystal, measuring as few as less than a dozen atoms, forms what is known as the latent image.
(The latent image formed by these miniscule amounts of silver can lay dormant for decades before being developed, however, this duration is dependant on the migration speed of silver atoms within the emulsion layer.)
Development:
In developing this latent image into a processed photo, a chemical agent must act upon the film to catalyze the further crystalization of metallic silver onto these latent silver atom centers. This chemical is known as a developer, as it unveils or de-velops the image seemingly from the ether; popular ingredients are Metol, Hydroquinone, Sodium Hydroxide, & Borax.
Fixation:
Following the desired development of the film or paper, a chemical is used which removes the remaining undeveloped silver halide. This is done with a chemical silver halides are known to be soluble in, primarily thiosulfate salts. Once fixing is completed, film or prints are then thoroughly washed to remove any remaining chemicals.
Proper care and archiving of photographic materials requires a neutral pH, low humidity, and stable temperatures preferably below that of generally accepted room temperature.
