Photographer's Note

Rio de Janeiro has the best blue sky of the world!
A romantic sentence? Not at all!
This is the U.K. National Physical Laboratory Report conclusion in july 2006.
This report describes the science and experiments behind the Blue Sky Explorers trip of a lifetime, to travel around the world, to discover where in the world has the ‘Best Blue Sky’!!
NPL is the UK's national measurement institute and is responsible for the establishment and maintenance of all physical measurement quantities e.g. the kilogram, second and the metre. Any measurement made in the UK is ultimately traceable to NPL. It is not only these well-known quantities that NPL is responsible for however, but also things like light and colour.
What is colour?
Colour is defined using a combination of three numbers (representing the colour selective receptors of the human eye, analogous to the Red, Green and Blue emitters of a television screen). By combining these three primaries, all colours can be realised or detected (perceived).
Colour fills our lives and affects our choices and preferences of objects as diverse as cars, clothes and food. It is used to promote corporate identity, to camouflage and provide information. Colour is among the ‘newest’ of measurements and significant advances are still taking place today.
The brain uses the sensation of colour to code proportions of different wavelengths of light. The colour of objects depends on: how they are illuminated, how they absorb or scatter light, and how our eyes and brains react.
As spectral information is encoded by the eye and brain into three signals, only three numbers are needed to represent all possible colours.
How do we measure colour?
To measure colour, instruments attempt to replicate the extremely complicated human visual function. They start by evaluating the relative amounts of spectral light emitted, reflected, or transmitted by objects, and convert these to colour values such as Hue, Brightness and Colourfulness using a model of the human visual system known as the ‘Standard Observer’.
The results from the NPL spectrophotometer analysis show that the Best Blue Sky ranking took the following order:
2-New Zealand
5-South Africa
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Photo Information
  • Copyright: Alberto Piubello (albertopiubello) Gold Star Critiquer/Silver Workshop Editor/Gold Note Writer [C: 331 W: 41 N: 881] (2623)
  • Genre: Luoghi
  • Medium: Colore
  • Date Taken: 2004-05-23
  • Categories: Natura
  • Esposizione: f/5.3
  • More Photo Info: view
  • Versione Foto: Versione Originale, Workshop
  • Date Submitted: 2007-03-02 17:13
Viewed: 3412
Points: 34
Additional Photos by Alberto Piubello (albertopiubello) Gold Star Critiquer/Silver Workshop Editor/Gold Note Writer [C: 331 W: 41 N: 881] (2623)
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