English Colour
Lancy Luitel
The Colour Contrast Check Tool allows to specify a foreground and a background colour and determine if they provide enough of a contrast "when viewed by someone having color deficits or when viewed on a black and white screen"[W3C].
The tool will indicate that the colours pass the test if both the colour difference and the brightness difference exceedtheir threshold. It will indicate that it sort of passes if only one of the two values exceed their threshold. And finally, it'll failto pass if neither value exceeds its threshold.
The tool will also indicate if the colours pass the newer WCAG 2.0 contrast ratio formula. The WCAG 2.0 formula differentiates between text smaller than 18pt text larger than 18pt (or text that is bold and larger than 14pt). For AA compliance, text should have a ratio of at least 4.5:1 (larger text, at least 3:1). For AAA compliance, text should have a ratio of at least 7:1 (larger text, at least 4.5:1).
While scientists, photographers, businessmen and experimenters laboured, the public became impatient. Photographers, eager to give their customers what they wanted, soon took the matter, literally, into their own hands and began to add colour to their monochrome images. As the writer of A Guide to Painting Photographic Portraits noted in 1851:
Several different processes and materials were used for hand-colouring, which proved to be a cheaper, simpler alternative to early colour processes. It provided studio employment for miniature painters who had initially felt threatened by the emergence of photography.
In skilled hands, effects of great subtlety and beauty could be achieved. However, even at its very best, hand-colouring remained an unsatisfactory means of recording colour; it could not reproduce the colours of nature exactly.
The scientific investigation of colour began in the 17th century. In 1666, Sir Isaac Newton split sunlight with a prism to show that it was actually a combination of the seven colours of the spectrum.
While this work was scientifically important, it was of limited practical value at first. Exposure times were long, and photographic materials sensitive to the whole range of the colour spectrum were not yet available.
The American photographer and inventor Frederic Ives devised a system based on three colour-separation negatives taken through coloured filters. From these negatives, positive transparencies were made which were placed in a special viewer, called a Kromskop. Mirrors in the Kromskop superimposed the images on the three transparencies and a second set of filters restored the colours.
The first process to use this method was devised by Dr John Joly of Dublin in 1894. Joly covered a glass plate with very fine red, green and blue lines (less than 0.1mm wide) in order to create a three-coloured filter screen.
When taking a photograph, this screen was placed in the camera in front of the plate. After exposure and reversal processing, the black-and-white positive image was carefully placed in register with another filter screen. The result was a colour transparency which could be viewed by transmitted light (light that passes through an object).
Next, charcoal powder was spread over the plate to fill any gaps between the coloured starch grains. A roller, using a pressure of five tons per square centimetre, was used to flatten out and spread the grains. The plate was then varnished to make it waterproof.
The final plate was a three-coloured filter screen: there were around four million transparent starch grains on every square inch of it, each grain effectively acting as a coloured filter. The final stage was to coat the plate with a panchromatic emulsion.
Following exposure, autochrome plates were reversal-processed to produce a positive image. When viewed by transmitted light passing through the plate, the millions of tiny red, green and blue-violet grains combined to give a full-colour photograph, accurately reproducing the colours of the original subject.
The commercial success of the process prompted the appearance of many other colour processes based on the concept of screens made up of microscopic colour filters. These screens used either a random grain pattern or, more commonly, different geometric patterns of lines and squares.
The original theory for subtractive colour reproduction can be traced back to the French physicist and inventor Louis Ducos du Hauron, who explained the method in his book Les couleurs en photographie, solution du problème (1869). Du Hauron proposed that colour separation negatives should be used to produce three positive images, which would then be dyed the complementary colours of cyan (bluegreen), magenta (blue-red) and yellow.
With subtractive colour, white, for example, is represented by clear glass or white paper rather than by light passing through three filters. This means that subtractive processes are much less wasteful of light.
To exploit the Vivex process, a company called Colour Photographs (British & Foreign) Ltd. was formed with a factory in Willesden, north London. This was the first laboratory to offer a colour print making service to professional photographers.
The basic idea of the tripack system was to construct a multi-layer unit, where each plate was coated with an emulsion sensitive to one of the primary colours. Light would pass through the first plate in order to reach the second emulsion layer and, in turn, pass through that plate to register on the third emulsion.
However, despite extravagant claims, the results were disappointing. The negatives from the second and third emulsion layers were so blurry that the company was reduced to hand-colour black-and-white prints made from the sharpest (front) element of the tripack. Unsurprisingly, Colour Snapshots Ltd went bankrupt in December 1929.
Kodachrome was the invention of Leopold Mannes and Leopold Godowsky. Both earned their living as professional musicians (Mannes played the piano and Godowsky the violin) while spending their spare time experimenting with colour photography. Despite their best efforts, there came a point when they were unable to progress without outside support.
Like Fischer, Mannes and Godowsky had great difficulty in preventing the coloured dyes spreading between the emulsion layers. They overcame this by putting the colour couplers in the developer rather than the emulsion.
There is growing interest in skin colour prediction in the forensic field. However, a lack of consensus approaches for recording skin colour phenotype plus the complicating factors of epistatic effects, environmental influences such as exposure to the sun and unidentified genetic variants, present difficulties for the development of a forensic skin colour predictive test centred on the most strongly associated SNPs. Previous studies have analysed skin colour variation in single unadmixed population groups, including South Asians (Stokowski et al., 2007, Am. J. Hum. Genet, 81: 1119-32) and Europeans (Jacobs et al., 2013, Hum Genet. 132: 147-58). Nevertheless, a major challenge lies in the analysis of skin colour in admixed individuals, where co-ancestry proportions do not necessarily dictate any one person's skin colour. Our study sought to analyse genetic differences between African, European and admixed African-European subjects where direct spectrometric measurements and photographs of skin colour were made in parallel. We identified strong associations to skin colour variation in the subjects studied from a pigmentation SNP discovery panel of 59 markers and developed a forensic online classifier based on naïve Bayes analysis of the SNP profiles made. A skin colour predictive test is described using the ten most strongly associated SNPs in 8 genes linked to skin pigmentation variation.
From around 1960 a more purely abstract form of colour field painting emerged in the work of Helen Frankenthaler, Morris Louis, Kenneth Noland, Alma Thomas, Sam Gilliam and others. It differed from abstract expressionism in that these artists eliminated both the emotional, mythic or religious content of the earlier movement, and the highly personal and painterly or gestural application associated with it. In 1964 an exhibition of thirty-one artists associated with this development was organised by the critic Clement Greenberg at the Los Angeles County Museum of Art. He titled it Post-Painterly Abstraction, a term often also used to describe the work of the 1960 generation and their successors.
Promoting development and applications of science and technology that underpin remote sensing of ocean colour across all aquatic environments (in-land, coastal, open ocean), through coordination, training, liaising between providers and users, advocacy, and provision of expert advice.
The International Ocean Colour Coordinating Group (IOCCG) is an international committee of experts comprised of representatives from national space agencies and research scientists from the aquatic radiometry user community. It was established in 1996 under the auspices of the Intergovernmental Oceanographic Commission of UNESCO, following a resolution endorsed by the Committee on Earth Observation Satellites (CEOS). IOCCG promotes development and applications of science and technology that underpin remote sensing of ocean colour across all aquatic environments (in-land, coastal, open-ocean) through coordination, training, liaison between providers (space agencies) and users (scientists), advocacy, and provision of expert advice. Objectives include developing consensus and synthesis at the world scale in the subject area of satellite ocean colour radiometry (OCR), establishing specialised scientific working groups to investigate various aspects of ocean colour technology and its applications, and addressing continuity and consistency of ocean colour radiance datasets through the CEOS OCR-Virtual Constellation. The IOCCG also has a strong interest in capacity building, and conducts and sponsors advanced ocean colour training courses in various countries around the world.
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