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The majority of black-and-white infrared art, landscape, and wedding photography is done using orange (Wratten #15 or 21), red (#23, 25, or 29) or visually opaque (#72) [d] filters over the lens to block the blue visible light from the exposure. Very dark-red (#29) filters block out almost all blue, and visually opaque (#70, 89b, 87c, 72 ...
Dispersive prisms are used to break up light into its constituent spectral colors because the refractive index depends on wavelength; the white light entering the prism is a mixture of different wavelengths, each of which gets bent slightly differently. Blue light is slowed more than red light and will therefore be bent more than red light.
An example of this phenomenon is when clean air scatters blue light more than red light, and so the midday sky appears blue (apart from the area around the Sun which appears white because the light is not scattered as much). The optical window is also referred to as the "visible window" because it overlaps the human visible response spectrum.
Generally, longer wavelengths (red) undergo a smaller deviation than shorter wavelengths (blue). The dispersion of white light into colors by a prism led Sir Isaac Newton to conclude that white light consisted of a mixture of different colors. Triangular prisms are the most common type of dispersive prism.
Blue light is absorbed by the structural proteins, enzymes, and protein metabolites found in the lens. [9] The absorption of blue light creates yellow pigments in the lens's protein. The lens progressively darkens and turns yellow. [9] Blue light is absorbed by the lens, preventing blue light from reaching the retina at the back of the eye. [12]
In a triangular prism, dispersion causes different colors to refract at different angles, splitting white light into a rainbow of colors. The blue color is more deviated (refracted) than the red color because the refractive index of blue is higher than that of red. The variation of refractive index with wavelength for various glasses.
If an image is recorded in tristimulus coordinates (or in values which can be converted to and from them), then the white point of the illuminant used gives the maximum value of the tristimulus coordinates that will be recorded at any point in the image, in the absence of fluorescence. It is called the white point of the image.
In optics, chromatic aberration (CA), also called chromatic distortion, color aberration, color fringing, or purple fringing, is a failure of a lens to focus all colors to the same point. [ 1 ] [ 2 ] It is caused by dispersion : the refractive index of the lens elements varies with the wavelength of light .