In photography, toning is a method of changing the colour of black-and-white photographs. In analog photography, toning is a chemical process carried out on silver-based photographic prints. The effects of these processes can be emulated with software in digital photography.
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Beginning in the 1880s, sepia was produced by adding a pigment, made from the Sepia officinalis cuttlefish found in the English channel[1], to the positive print of a photograph. The term 'sepia' comes from the name of the pigment.
Most toners work by replacing the metallic silver in the emulsion with a silver compound, such as silver sulfide (Ag2S) in the case of sepia toning. The compound may be more stable than metallic silver and may also have a different colour or tone. Different toning processes give different colours to the final print. In some cases, the printer may choose to tone some parts of a print more than others.
Toner also can increase the range of visible shades visible in a print without reducing the contrast. Selenium toning is especially effective in this regard. Some toning processes can improve the chemical stability of the print, increasing its potential longevity. Other toning processes, such as iron and copper toners, can make the print less stable. Many chemical toners are highly toxic. It is extremely important that the chemicals are used in a well ventilated area. Rubber gloves and face protection should be worn when handling them. Some toners contain chemicals that are carcinogenic.
Selenium toning is a popular archival toning process, converting metallic silver to silver selenide. In a diluted toning solution, selenium toning gives a red-brown tone, while a strong solution gives a purple-brown tone. The change in colour depends upon the chemical make-up of the photographic emulsion being toned. Chlorobromide papers change dramatically, whilst pure bromide papers change little. Fibre-based papers are more responsive to selenium toning.[2]
Selenium toning may not produce prints quite as stable as sepia or gold toning. Recently, doubts have surfaced as to the effectiveness of selenium toner in ensuring print longevity.[3]
Sepia toning is a specialized treatment to give the photograph a warmer tone and to enhance its archival qualities. Chemicals are used to convert the metallic silver in the print to a sulfide compound, which is much more resistant to the effects of environmental pollutants such as atmospheric sulfur compounds. Silver sulfide is at least 50% more stable than silver.[4]
There are three types of sepia toner in modern use;
Except for polysulfide toners, sepia toning is done in three stages. First the print is soaked in a potassium ferricyanide bleach to re-convert the metallic silver to silver halide. The print is washed to remove excess potassium ferricyanide then immersed into a bath of toner, which converts the silver halides to silver sulfide.
Incomplete bleaching creates a multi-toned image with sepia highlights and grey mid-tones and shadows. This is called split toning. The untoned silver in the print can be treated with a different toner, such as gold or selenium.[5]
Metal replacement toners replace the metallic silver, through a series of chemical reactions, with a ferrocyanide salt of a transition metal. Some metals, such as platinum or gold can protect the image. Others, such as iron (blue toner) or copper (red toner) may reduce the lifetime of the image.[citation needed]
Metal replacement toning with gold alone results in a blue-black tone. It is often combined with a sepia toner to produce a more attractive orange-red tone. The archival Gold Protective Solution (GP-1) formula uses a 1% gold chloride stock solution with sodium or potassium thiocyanate.[6] It is sometimes used to split tone photographs previously toned in selenium for artistic purposes.[7]
Dye toners replace the metallic silver with a dye. The image will have a reduced lifetime compared with an ordinary silver print.[citation needed]
Toning can be simulated digitally, either in-camera or in post-processing. The in-camera effect, as well as beginner tutorials given for software like Photoshop or GIMP, use a simple tint. More sophisticated software tends to implement sepia tones using the duotone feature. Simpler photo-editing software usually has an option to sepia-tone an image in one step.
The examples below show a digital colour photograph, a black and white version and a sepia-toned version.
 Colour image |
 Grayscale image |
 Sepia-toned image |
The following are examples of the three types using film:
 Colour photograph |
 Black-and-white photograph |
 Sepia toning |
   | Sepia-toning - Sepia Toning with The GIMP |
| | Sepia-toning in Photoshop. - Digital Black and White Conversion in Photoshop |
| | How To: Create sepia toned images - Create sepia toned images |
| | .NET Matters, Sepia Tone - .NET Matters: Sepia Tone, StringLogicalComparer, and More |
| | Sepia-toning - Sepia toning - a digital imaging guide |
| | Large version of the Native American photo - Welcome to HistoryNYC + Historical Maps, Poster, Books and Custom Framing. |
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