Home Assignment

Subject :- Computer Graphics

Title of Home Assignment : COLOR MODEL

Type of Assignment  : BLOG

Name of Group Members :-   

1. Prathamesh Sunil Gathadi - 119C0023
2. Govinda Darade  - 119C0027 
3. Sanket Borkar - 119C0028
4. Paras Barhate - 119C0030
5. Vandan Kulkarni - 119C0047

COLOR MODEL

How do we actually see colors ?

In our retina there are cones and rods. With around 5 million cones we will observe colors and with about 120 million rods we observe clarity. We have separate cones for light with low frequencies (red tones), medium frequencies (green tones) and high frequencies (blue tones). So in fact you could say that the human eye is already working with RGB.

But in order to be able to perceive those colors, there must be sufficient light. If there's insufficient light, we don't perceive colors. However, we can still observe silhouettes and figures in the dark. Because we have 24 times as many rods as cones, we can no longer perceive colors at night, but we still see silhouettes and shapes in the form of shades of gray.

Color Model

A color model may be a thanks to describe colors during a color system. Most color models have 3 dimensions, like the simplest known: RGB. From Red, Green and Blue. And because of the three dimensions, a color system can be represented with 3 axes, so in 3D.

You could say that each one models ultimately all begin at RGB. But usually we don't distinguish one, but two main color models, which also are the simplest known; RGB and CMY. These color models can be further subdivided into sub-color models. For example, RGB has for instance sub-models HSL and HSV. More about that later.

For now here's just a list of some well-known color models:

• RGB
• HSV/HSB
• HLS/HSL
• CMY(K)
• LAB
• NCS

Additive color mixing and light

Light is thus perceived by the R, G and B cones and brightness rods in our eyes. Ultimately, everything we call color is actually just light. Different colored light rays can be mixed together by overlapping each other. Just think of two spots where the rays intersect. This method of color mixing is named additive, because colored lights that overlap/mix are added together and that we then observe the results of that addition with our eyes.

The basic colors for additive color mixing are normally red, green and blue. Just like the cones in our eyes. Red, green and blue are therefore the first colors for additive color mixing, or light mixing. And if you add all three together (overlapping each other) you get...

Subtractive color mixing and paint

        So color is in fact light. But not every ray of sunshine directly reaches our eye. Most of the sunshine finishes up on objects around us. Some parts of this light can get absorbed by these objects, so that we only perceive the remaining light as color.

If we have a theoretical lamp that emits perfect white light, this means that this lamp emits all possible colors that together make up white light. With this lamp shining on a white sheet of paper that paper will reflect all the colors of the white light and we see a white sheet of paper.

If we now hold the same white light above a red sheet of paper, the green and blue hues will be absorbed by the paper and we will only see the red part of the light so that we see a red sheet of paper. A colored object therefore filters incoming light and reflects only the light that remains, so that we perceive the object colored. A black object does not reflect light at all, so we perceive a black object.

That's how it works with paint. And you can mix paint. A child quickly understands that if you mix yellow paint with cyan paint (a child could call it light blue) you get green. Yellow paint absorbs from the incoming white light all the blue light rays and therefore the cyan paint absorbs all the red rays from the sunshine , so we perceive green.

For everything that's not light itself, but filters light and reflects, so for instance ink and paint, the first colors are Cyan, Magenta and Yellow (CMY). When blending paint or ink, it doesn't add up as with mixing light, but it's subtracted from each other. That is why we call this subtractive mixing. Thus, with subtractive color mixing, exactly the opposite happens to additive color mixing. The colors cyan, magenta and yellow overlapping one another don't form white, but...?

Primary, secondary and tertiary colors

          To build and describe a color system, three primary colors are usually mixed further until a color palette arises. The secondary colors are created by mixing two primary colors. By mixing three primary colors the tertiary colors are created, and so on. So:

·          Primary colors

The basic colors with which you (in theory) can mix all colors. With RGB these are red, green and blue. With CMY these are cyan, magenta and yellow.

·         Secondary colors

The colors you get when you mix two primary colors.

·         Tertiary colors

The colors you get when you mix three primary colors.

By playing with the following interactive you get more insight per color model into the primary, secondary and tertiary colors and how they are put together. You can rotate the wheel for a different perspective if you like

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In the wheel you can see that the primary, secondary and tertiary colors of the CMY model are always the opposite of those of the RGB model. And that is understandable, of course, given that one model adds colors and the other subtracts them.

The RGB color model

            In many graphic software programs, like Photoshop, Illustrator, Affinity Designer or Affinity Photo, you'll mix colors within the RGB model with sliders for Red, Green and Blue. But to offer you more insight, below is an interactive 3D view of the RGB color model as a cube, because it is usually displayed.
The cube has three axes; Red, Green and Blue. And every point within the cube may be a unique mixed color. You will find all possible mixed colors. Turn the cube around to get more insight into the model.

The HSV color model

            HSV stands for Hue, Saturation and Value. This model is also sometimes called HSB, where the B stands for Brightness. But that is exactly the same model. If I write about HSV below, the same applies to HSB.

If you use the HSV model in graphics software, you often see three sliders and a graphical representation to instantly choose a color with the corresponding brightness and saturation:

• Hue:

Color tint. The rotation on the cone edge between 0 to 360 degrees. 0 degrees is red, 120 degrees is green and 240 degrees is blue.

• Saturation:

From 0% for grayscale (no color) to 100% for complete pure color. 0% is that the center of the cone and 100% the outer circumference.

• Value:

Brightness. 0% is totally dark, 100% is totally light. Where 0% is the bottom of the cone and 100% the top.