Natura e Concetto del Colore

• Color perception integrates human experience, crucial in aesthetics and conveying information (e.g., traffic lights).

Nature and Concept of Colour

• Color's nature has been debated for centuries, lacking a universally accepted definition.
• It is typically accepted that color exists within the observer's mind / psyche, not as an objective entity.
• Color is seen as an attribute of visual experience and the mechanism involves an external physical agent (light), an internal physiological process (retina's cones and rods), and intellectual processing at a psychic level.
• The subjective nature of color sensation doesn't negate a scientific approach, focusing on objectively measurable physical quantities.

Additive Composition: Grassmann's Law

• Two physical quantities determine chromatic sensation: incident beam power and spectral composition.
• Color intensity expresses the physical stimulus's quantitative effect, measured photometrically (e.g., luminous flux).
• Hue expresses the physical stimulus's qualitative properties, characterized by the dominant wavelength.
• Saturation expresses the percentage importance of the dominant wavelength relative to other wavelengths in the beam.
• The human eye's response to luminous radiation is primarily qualitative, depending on both power and spectral composition.
• A monochromatic beam's chromatic sensation is not uniquely tied to that beam.
• A given color can be reproduced by mixing three primary colors, which are conventionally chosen.
• Algebraically, R, G, B represent primary colors and r, g, b represent their respective quantities in a mixture to realize a quantity of the desired color C.
• The symbolic representation is c(C) = r(R) + g(G) + b(B), additive composition where R, G, and B are taken in quantities r, g, and b, reproducing the chromatic sensation of quantity c of color C.
• Practically, additive composition can be achieved with three projectors, projecting R, G, and B light beams.
• Adjusting each projector's luminous flux allows quantity determination of each beam to reproduce the desired color C at quantity c.
• The equation 20.1 cannot be interpreted in a strictly algebraic sense.
• Equality between the equation's two terms indicates the observer judges the chromatic sensations produced by the radiation C to be equivalent to those produced by the additive combination of the three primary colors R, G, and B.
• Symbols R, G, and B express selected primary colors' quality, while r, g, and b express radiated amount to realize color equivalence.
• Primary color selection is arbitrary in principle.
• While a broad color range can be imitated with additive mixing, some colors are impossible to imitate, which is irrespective of primary triad choice.
• Changing the primary triad could reproduce formerly unobtainable colors, but at the cost of losing replicability for others.
• Even with increasing primary components, some colors will remain unreproducible, therefore, it is not justified to say red, green and blue can be used to reproduce all colours.
• Additive composition of red, green and blue gives the most extensive possible range of colours
• Combining two primary colors produces yellow (red + green), cyan (green + blue), and magenta (red + blue).
• Combining all three in equal measure reproduces white, instead of which you might get colour C according to equation 20.1.
• It is impossible to distinguish each component inside the colours in a mixture as the eye is a synthetic organ, unlike the ear
• When a certain colour C is irreproducible from a mixture of three primary colours, mix the colour C with a colour from the three components in order to reproduce the mixture of the other two. Expressed in a symbolic way c(C) + r(R) = g(G) + b(B) either to c(C) + g'(G) = r'(R) + b'(B) or even c(C) + b"(B) = r"(R) + g"(G).
• The quantities of each colour to use in order to attain an equality can be miniscule
• Sometimes it can be necessary to mix two colours to obtain colour C with the third component.
• Primary luminous flux levels added to the inimitabile color c(C) for chromatic equivalence are considered negative.
• Introducing this specification enables identifying any color via three numbers (±r, ±g, ±b), each representing the luminous flux level.
• Final relation gives a colour that can be represented with three numbers i.e. (+r"; -g"; -b").
• The colorimetric equations represent Grassmann's Law.
• When additive method is used and there are no projectors, quantities r, g, and b can have a different physical meaning that luminous flux.
• For instance, using colour quantities mean how much each colour from the three to obtain the desired colour.
• The relation c=r+g+b has to be taken with its value in an algebraical sense as well.

Specification Curves

• Assuming a primary triad R, G, B is selected, indicated by dominant longitudes AR, AG, λβ, now we try to reproduce a colour C whose colour is characterised by a dominant longitude.
• To attain this goal from each ingredient in the equation a quantity has to be taken corresponding to ra, ga, b. Which is C₂(C) = r(R) + g(G) + b₂(B).
• Is a colour the same as C' whose colour is characterised by a longitude d', quantities of each triad's primary color have to be taken different from the previous ones.
• This operation needs to repeated ideally for all colours whose colour is characterised by a longitude which varies from 400 nm to 700 nm.
• In that case, for each component of the selected primary triad it's possible to outline a scheme where the absinthe indicates the longitude that characterises each colour C and the level indicates each component which has to be taken from the colour C.
• If regulators of the three projectors' luminous flux are set in a way that, on a screen, a quantity corresponding to 235 lumen is projected in red (650 nm), 180 lumen in green (530 nm) and 0 lumen in blue (425 nm), a mix will be obtained with 415 lumen whose colours corresponds to a 600 nm longue d'unde.
• A colour C whose colour is comprised in the interval is unattainable with the current triads but may be realised using mixing in a method that is c(C) + r(R) = g(G) + b(B)
• To avoid negative regulators, the International Illumination Commission (CIE) set a primary triad in 1931, the longue d'unde of which are respectively
  • red: 700nm
  • green: 546,1 nm
  • bleu : 435,8 nm

Tricromatic Coefficients: Chromatic Diagram

• The preceding curves are called universal CIE curves for coloring.
• Quantities r, g, b indicate the trickomatic coordinates.
• The Universal CIE curves are expressed in arbitrary units, the areas of which are equal.
• Dominant longitude 460 nm means the curves of 20.7 are determined by the triad: r=0,3 g=0,07 b=0,85
• Color identification through tricromatic coordinates makes the three- dimensional graphic representation difficult. In order to get around this difficulty, is used the following mathematical artifice:
  • x=r/r+g+b' y=g/r+g+b' z=b/r+g+b (20.2)
  • Note that the adimensional quantities x, y, z, which we call tricromatic coefficients, are linked together by the rapport x+y+z=1
  • Known quantities x and y the third part it can be determined immediately, given that z=1-(x+y)
• In short a colour the determination of a colour now can be set in the following method;
  • the first thing to do is mark down the dominant wavelength longitude, then the values of the three coordinates r,g,b are found on the curves CIE
  • Second, the values of the coefficients are calculated xy with the above equation 20,2 and on a two-dimensonal graphic on a XY plain it is reported, then that is the graphic representation of certain length longitude.

Purity and Tint of Colour

• In the colour scheme the colours whose coefficients x and y show dots of the chromatic curve are told spectral colour it even are named spectral colours.
• Real colours on the other hand indicate all the colours on the diagram.
• Now W is the point of the white colour and xw, yw, are the trickromatic equations.
• Let’s take a generic color C with coefficients cx, cy as in the figure 20.11.
• To join W with C until the pure colour on the point A of coefficient xa, ya
• colour C can be seen such way which is an addition of W e A secondo la relanotte:
  • k, the position of the dot C is such which is closer to the incoming mixture and with a high percentage
  • This is done because such way (i.e.) if i am mixing and i want to attain A which is 60%, then dot C is closer to A then W
  • Made the above, the we can set an equation either purity or an unsaturation of a colour
    • P=WC/WA.
• From the above equation, an equation that shows the purity
• When colour C is on the side is evident the degree of purity is 1, as indeed, wa/wa equals one!
• This is something to keep an affirmed such that we a have a clear view of pure or fully saturation.

The porpoises - the compliments

• If the dot of while is added at the point representative from the colour pure(400 nm) and the point from 700 nm, there will be a triangle of wbr.
• Let P be the internal point within a trianf and add P with W then C is not to be considered as mix of and w because and if colour does not show on he tria
• The colours here referred are given name of porpoise.
• the longitude of the porpoise P it is obtainable at the intersection of what is on the part on side ofw.

Color of the Bodies

• Is one to forget, then its either a solar radiation source or other, the colours are achieved through the objects.
• A colours attributed at the objects, therefore, it is not to say is an intrinsic, unless not its a combination of the lights.
• If said that, if the thing, the object is light its still the case, and still the colour is there is light, and so its there as will its most likeable.