What is called color gamut? It defines the specific range of the spectrum visible to the human eye. Because the colors that imaging devices such as digital cameras, scanners, monitors, and printers can produce vary, a specific gamut is used to match them.
Additive and subtractive types
There are 2 main types of color gamut - RGB and CMYK.
Additive gamma is formed by mixing light of different frequencies. Used in displays, TVs and other devices. The RGB name is made up of the initial letters of the red, green and blue light used for this generation.
Subtractive gamma is obtained by mixing dyes that block the reflection of light, resulting in the desired color. Used for publishing photographs, magazines and books. The abbreviation CMYK is made up of the names of the pigments (cyan, magenta, yellow and black) used in printing. The CMYK color gamut is significantly smaller than the RGB space.
Standards
Color gamut is regulated by a number of standards. Personal computers often use sRGB, Adobe RGB, and NTSC. Their color models are shown on the color chart as triangles. They are RGB peak coordinates connected by straight lines. The larger the area of the triangle, the more shades the standard can display. For LCD monitors, this means that a product compatible with a larger model can display a wider range of colors on the screen.
sRGB
The color gamut for personal computers is defined by the sRGB international standard established in 1998 by the International Electrotechnical Commission (IEC). It has taken a strong position in the Windows environment. In most cases, displays, printers, digital cameras, and various applications are calibrated to reproduce the sRGB model as accurately as possible. As long as the devices and programs used to input and output image data are compliant with this standard, discrepancies between input and output data will be minimal.
Adobe RGB
The chromatic diagram shows that the range of values that can be expressed using the sRGB model is rather narrow. In particular, the standard excludes highly saturated colors. This, and the development of devices such as digital cameras and printers, has led to the widespread use of technology capable of reproducing tones that are not in the sRGB range. In this regard, the Adobe RGB standard has attracted general attention. It is characterized by a wider color gamut, especially inarea G, that is, due to the ability to display brighter green tones.
The Adobe RGB standard was established in 1998 by Adobe Systems, which created the famous Photoshop photo retouching software series. While not international (like sRGB), thanks to Adobe's high market share of graphics applications in the professional imaging environment, as well as in the print and publishing industries, it has become de facto so. An increasing number of monitors can reproduce most of the Adobe RGB color gamut.
NTSC
This analog television standard was developed by the US National Television Systems Committee. Although the NTSC color gamut is close to Adobe RGB, its R and B values are slightly different. sRGB takes up about 72% of the NTSC range. Monitors capable of displaying the NTSC model are essential for video production, but are less important for individual users or still image applications. sRGB compatibility and the ability to reproduce the Adobe RGB color gamut are key to displays used for photography.
Illumination technologies
In general, modern monitors used with PCs, due to the specifications for their LCD panels (and controls), have a color gamut that includes the entire sRGB space. However, given the growing demand for wider gamut reproduction, the monitors' color space has been expanded. In this case, the Adobe RGB standard is used as the target. But how does this happenextension?
This is largely due to improved backlighting. There are 2 main approaches. One of them is to expand the color gamut of cold cathodes, which is the main backlight technology, and the other is to affect the LED backlight.
In the first case, a quick solution is to increase the color filter of the LCD panel, although this reduces the brightness of the screen at the expense of light transmission. Increasing the brightness of the cold cathode to counteract this effect tends to shorten the life of the device and often results in illumination disturbances. The efforts of engineers to date have largely overcome these shortcomings. In many fluorescent-backlit monitors, range extension is achieved by modifying the phosphor. It also reduces the cost as it allows you to expand the color gamut without major changes to the existing design.
The use of LED lighting has been on the rise relatively recently. This allowed higher levels of brightness and color purity to be achieved. While there are some disadvantages, including poorer image stability (due to radiant heat issues, for example) and difficulties in achieving white uniformity across the entire screen due to the RGB LED blend, these issues have been addressed. LED backlighting costs more than fluorescent lamps and has been used less, but because of its effectiveness in widening the display's color gamut, adoption of this technology has increased. This is trueand for LCD TVs.
Ratio and coverage
Manufacturers often indicate the monitor's color gamut (i.e. triangles on the color chart). Many of you have probably seen in the catalogs the ratio of the gamma of any device to the Adobe RGB or NTSC model.
However, these figures only speak of area. Very few products cover the entire Adobe RGB and NTSC space. For example, the Lenovo Yoga 530 has a color gamut of 60-70% Adobe RGB. But even if the display shows 120%, it is impossible to tell the difference in values. Since such data leads to misinterpretation, it is important to avoid confusion with product characteristics. But how to check the color gamut of the monitor in this case?
To eliminate specification issues, some manufacturers use "coverage" instead of "area". It is obvious that, for example, an LCD monitor with 95% Adobe RGB color gamut can reproduce 95% of the gamut of this standard.
From the user's point of view, coverage is a more convenient and understandable characteristic than area ratio. Although there are difficulties, showing the color gamut of the monitors that will be used for color control on graphs will certainly make it easier for users to form their own judgments.
Gamma conversion
When checking the color space of a monitor, it is important to remember that wide color gamut does not necessarily translate into high image quality. This may causemisunderstanding.
Color gamut is a characteristic used to measure the image quality of an LCD monitor, but it alone does not define it. The quality of the controls used to realize the full potential of the display is critical. As such, the ability to generate accurate tones suitable for specific needs outweighs having a wider color gamut.
When evaluating a monitor, you need to determine if it has a color space conversion function. It allows you to control the display gamma by setting a target model such as Adobe RGB or sRGB. For example, by selecting the sRGB mode from the menu, you can set your monitor to Adobe RGB so that the colors displayed on the screen fall within the sRGB range.
Displays that offer color gamut conversion functions are compatible with Adobe RGB and sRGB standards at the same time. This is essential for applications that require accurate tone generation, such as photo editing and web production.
For purposes that require accurate color reproduction, in some cases the disadvantage is that the monitor with wide color gamut does not have a conversion function. Such displays display each tone of the 8-bit gamut in full color. As a result, the generated colors are often too bright to display sRGB images (i.e. sRGB cannot be reproduced accurately).
Converting an Adobe RGB photo to sRGB results in loss of highly saturated color data and loss of tonal subtleties. Thus, the pictures becomefaded and jumps in tone appear. The Adobe RGB model can produce richer colors than sRGB. However, colors actually displayed may vary depending on the monitor used to view them and the software environment.
Improve image quality
Where the monitor's wider color gamut allows for a greater range of tones, more control over tones, and finer adjustments to screen images, problems such as tonal gradation distortion, color variations caused by narrow viewing angles, and display unevenness, less visible in the sRGB gamuts, have become more pronounced. As mentioned earlier, the mere fact of having a wide color gamut display does not guarantee that it will provide high quality images. It is necessary to take a closer look at the various technologies for using the extended RGB color gamut.
Gradation increase
The key here is the built-in gamma correction function for multi-level tonal transitions. The 8-bit input signals for each RGB color that come from the PC side are dithered to 10 or more bits per pixel on the monitor, and then assigned to each RGB color. This improves tonal transitions and reduces color gaps, improving the gamma curve.
Viewing angles
Larger screens usually make it easier to see the difference, especially in devices with a wide color gamut, but they can have color problems. Mostly color variation due to viewing angledetermined by LCD panel technology, with the best of them showing no tone shift even when viewed from a wide angle.
Without getting into the specifics of display manufacturing, they can be divided into the following types, listed in ascending order of color change: in-plane switching (IPS), vertical alignment (VA) and twisted nematic crystals (TN). Although TN technology has advanced to the point where its viewing angle performance has improved significantly, there remains a significant gap between it and VA and IPS technologies. If color accuracy is important, VA and IPS panels are the best choices.
Uneven color and brightness
The non-uniformity correction function is used to reduce display unevenness regarding screen color and brightness. A well-performing LCD monitor produces little unevenness in brightness or tone. In addition, high-performance displays are equipped with systems that measure brightness and color at each point on the screen and correct them by their own means.
Calibration
In order to fully realize the capabilities of a wide gamut LCD monitor and display tones according to the user's needs, it is necessary to consider the use of adjustment equipment. Display calibration is the process of measuring the colors on the screen using a special calibrator and reflecting the characteristics in the ICC profile (file that determines the color characteristics of the device) used by the operating system.system. This ensures that the information processed by graphics software and other software and the tones generated by the LCD monitor are consistent and highly accurate.
Keep in mind that there are 2 types of display calibration: software and hardware.
Software tuning is performed using specialized software that sets parameters such as brightness, contrast and color temperature (RGB balance) through the monitor menu and brings the image closer to the original tone using manual settings. In some cases, graphics drivers take over these functions instead of the program. Software calibration is low cost and can be used to adjust any monitor.
However, color accuracy may fluctuate due to human error. This can affect RGB gradation, as display balance is achieved by increasing the number of RGB output levels using software processing. However, it is easier to achieve accurate color reproduction with software than without it.
On the contrary, hardware calibration provides a more accurate result. It requires less effort, although it can only be used with compatible LCD monitors, and comes at a cost.
In general, calibration includes the following steps:
- program start;
- matching screen color characteristics with their target values;
- Direct control of brightness, contrast and gammadisplay correction at the hardware level.
Another aspect of hardware customization that shouldn't be overlooked is its simplicity. All tasks, from preparing the ICC profile for the adjustment results and writing them to the OS, are performed automatically.
In conclusion
If your monitor's color reproduction is important, you need to know how many colors it can actually represent. Manufacturers' specs listing the number of tones are generally useless and inaccurate when it comes to what a display actually displays versus what it's theoretically capable of. Therefore, consumers should be aware of the color gamut of their monitor. This will give a much better idea of its capabilities. You need to know the monitor's gamma coverage percentage and the model it's based on.
Below is a short list of common ranges for different levels of displays:
- Medium LCD covers 70-75% of NTSC gamut;
- Professional LCD monitor with 80-90% extended coverage;
- LCD display with cold cathode backlight - 92-100%;
- Wide-gamut LCD monitor with LED backlight - over 100%.
Finally, remember that these numbers are correct when the display is fully calibrated. Most monitors go through a basic setup and have slight deviations in some indicators. As a result, those who need highly accurate color must correct it with the appropriate profiles and settings using a special color calibration tool.tool.
