An Introduction Of RGB and CMYK
RGB vs. CMYK
Introduction: The simplest explanation of the difference between RGB and CMYK is that one describes how colors are displayed on a computer screen (RGB), and the other describes how colors are represented on inked paper (CMYK). An easy way to understand the difference between RGB and CMYK is to compare how an image looks when printed (CMYK), to how it looks on your computer monitor (RGB). Visible Light Spectrum Any discussion about color is based on how our eyes perceive light, so let’s take a quick look at light before we discuss RGB and CMYK. Light is composed of different wavelengths, which, grouped together, are called a spectrum. The human eye can only detect a portion of the entire light spectrum (i.e. we can’t see infrared and/or ultraviolet light). The portion we can see is what is referred to as the visible light spectrum. One end of the visible light spectrum contains short wavelengths of light which we see as violet. At the other end of the spectrum are the longer wavelengths we perceive as red. In between these two extremes are all the other colors we see in the natural world. If you look at the visible light spectrum below, you notice that when you divide it into thirds, the predominant colors are red, green and blue – the primary colors of the visible light spectrum. RGB RGB stands for red, green, and blue, the three primary colors of light. RGB is an ‘additive color’ process where color is produced by the light emitting from your monitor. In this process, the three primary colors of light are combined in various proportions to produce any color in the visible spectrum. For example, if green and blue are added together, cyan is produced Or, when blue and red are combined, magenta is the result. Combining the same amounts of all three primary colors - red, green, and blue light - produces white. An absence of all colors results in black. This is the principle behind how colors are displayed on computer monitors, TVs, image scanners, and mobile phone displays. Note: RGB is ‘device dependent’. In other words, the way colors are displayed on a screen depends on the hardware used to display it on that screen. So, colors in the same image might look slightly different when viewed on different monitors. CMYK CMY (Cyan, Magenta, and Yellow) are the primary colors used in printing inks - which are composed of dyes and pigments. These three colors are used in printing because virtually any visible color can be created simply by mixing them in various amounts. CMY is a ‘subtractive color’ process, which works by subtracting the colors of light reflected on a piece of white paper. In other words, each color of ink on the paper reduces the light that would otherwise be reflected and seen by our eyes. For example, when light falls on red ink printed on white paper, it absorbs (subtracts) all the colors from light except red. Hence this process is called a ‘subtractive color’ process. In theory, when combined, CMY (Cyan, Magenta, Yellow) should produce black. However, due to minor impurities contained in inks, the result is often a muddy dark brown. For this reason, black is added as a fourth printing ink. Black is also recognized as a ‘key’ color, hence it is designated with the letter ‘K”. CMYK is the color process used by both personal and commercial color printers. Color printers print images using just these four colors. (Some special-purpose "photo" printers use six colors - by adding a light cyan ink and a light magenta ink). Remember: Dyes and pigments do not produce as wide a range of colors as light. So, when an image is printed on paper, there is often an unwanted change in tones, and the colors may be more muted than they are on a computer monitor. |