(Redirected from Orthochromatic)

In chemistry, orthochromasia is the property of a dye or stain to not change color on binding to a target, as opposed to metachromatic stains, which do change color. The word is derived from the Greek orthos (correct, upright), and chromatic (color). Toluidine blue is an example of a partially orthochromatic dye, as it stains nucleic acids by its orthochromatic color (blue), but stains mast cell granules in its metachromatic color (red).

In spectral terms, orthochromasia refers to maintaining the position of spectral peaks, while metachromasia refers to a shift in wavelength, becoming either shorter or longer.

In photography, an orthochromatic light spectrum is one devoid of red light.

Orthochromatic photography edit

This WW II British Hawker Tornado prototype's 'Type A.1' RAF roundel's outermost, chrome yellow ring renders as dark gray, due to orthochromasia.
The Union Jack on orthochromatic emulsion at the South Magnetic Pole in 1909.

Orthochromatic photography refers to a photographic emulsion that is sensitive to only blue and green light, and thus can be processed with a red safelight. The increased blue sensitivity causes blue objects to appear lighter, and red ones darker. A cyan lens filter (which removes red light) can be used with standard panchromatic film to produce a similar effect. This type of emulsion was a significant advancement in early photography, as it allowed for the production of images with more accurate tonal reproduction than the earlier blue-sensitive emulsions. [1]

The development of orthochromatic films can be traced back to the work of Hermann Wilhelm Vogel in 1873. Vogel experimented with adding small amounts of certain aniline-based dyes to photographic emulsions to extend their sensitivity beyond blue light. This breakthrough allowed for the production of emulsions that could capture a broader spectrum of colors and tones including Josef Maria Eder, who introduced the use of the red dye erythrosine in 1884.[2]

Comparison between orthochromatic and panchromatic film.

In addition to their use in still photography, orthochromatic films also played a significant role in the early days of motion pictures. The improved tonal range provided by orthochromatic emulsions allowed filmmakers to create more visually compelling and realistic moving images.

One interesting technique used with orthochromatic films involved the use of a cyan lens filter. By using a cyan filter that removes red light, photographers could achieve a similar effect to orthochromatic films with standard panchromatic emulsions. This technique allowed photographers to manipulate the tonal range of their images without relying on specialized orthochromatic films.

Despite the advancements in photographic technology that have occurred since the introduction of orthochromatic films, they continue to be appreciated by some photographers for their unique tonal qualities and artistic potential.

See also edit

References edit

  1. ^ Hulfish, David Sherrill (1970) [first published 1915]. Motion-Picture Work: The Literature of Cinema. Ayer Publishing. p. 206. ISBN 978-0405016172.
  2. ^ Glossary: Photography: Orthochromatic. Archived from the original on 2006-09-24. Retrieved 2012-09-27. {{cite book}}: |work= ignored (help)