In display electronics, LED calibration plays an important role in maintaining picture quality, color and brightness. An uncalibrated LED screen produces significantly poor image quality, which is disadvantageous for professional uses such as advertising, photography and digital signage. This article will help you understand the key aspects of LED calibration, the types of LED calibration and its role in the industry.
The Role of LED Calibration
The process of adjusting the LED levels in a display to produce uniform color wavelength, brightness and contrast is known as LED calibration. LED calibration ensures that the various LED modules in a display produce colors with minimal variation, thus producing the highest quality image. In order to achieve LED calibration, special cameras known as colorimeters are used in combination with software tools such as Novastar or Colorlight.
LED CalibrationIn large screen LED displays, outdoor signage and broadcast media, LED calibration has become a necessary performance measure. It is often done after manufacturing and before delivery. Without LED calibration, the visual quality of a display may suffer drastically. Images may appear washed out, colors may be inaccurate and viewing may cause eye strain.
LED calibration has become a standard process in various industries. In consumer electronics, it is done to ensure high quality end-user entertainment. In the medical field it is used to make sure that imaging tools meet the DICOM standards. In commercial and outdoor settings, it is performed to make sure that visual quality remains unchanged in varying weather and light conditions.
Types of LED Calibration
There are several types of LED calibration that address different aspects of image quality or use different methods. Let us discuss the fundamental types of LED Calibration.
Relative Calibration
Relative calibration is the process of calibrating LED displays in order to ensure uniformity of color and brightness, while minimizing the amount of variation across the various LED modules. The Relative calibration is performed by display manufacturers after manufacturing the screen. Tools like colorimeters, spectrometers and light meters are used along with calibration software.
First, the variation in color and intensity is measured across the various LED modules. Thereafter, the LED levels are adjusted to bring the LED intensity down to a common level for all the modules. The objective of relative calibration is to bring the CV value of the LEDs from 7-10% down to less than 1%.
After comparison is done across all the LED modules, adjustment is done using calibration software that fine-tunes the settings across the entire LED array. This entire process is repeated iteratively in order to achieve the ideal CV value of 0.5% across all LED modules.
LED Screen CalibrationAbsolute Calibration
Absolute calibration is a method of LED calibration that is aimed at achieving not only brightness uniformity but also color realism. In absolute calibration, the LEDs of a screen are not only optimized for relative brightness, but also adjusted in reference to an external color standard. This means that the LED levels can be reproduced across different devices.
Absolute calibration is done using high-precision tools such as spectrophotometers, photometers and colorimeters. These devices are used to measure various LED parameters such as luminous intensity, color temperature, chromaticity coordinates, luminous flux and spectral power distribution. These are then adjusted using reference values from standardized color spaces.
Absolute calibration is a complex and expensive process that is usually recommended for professional LED displays. In high end televisions, broadcast systems and large displays, absolute calibration can produce true-to-life color realism.
Common Parameter Calibration
The common parameters of LED calibration are brightness, color, uniformity and gamma. Daily maintenance is another important aspect of LED display calibration, and it helps increase the life of the device significantly. Let’s discuss these calibration parameters in detail.
Brightness Calibration
In a newly manufactured LED display, the typical variance of brightness ranges from 10 to 20 per cent. After undergoing calibration for brightness, the various LEDs in your display are turned down to the brightness value for the weakest portion of your screen. For example, if the least bright module of your LED screen is 1000 nits, then other modules will be turned down to the same value for calibration.
Brightness calibration is important because it not only affects the quality of the image but also the lifespan of the LED. The heat produced by LEDs cause the panel to depreciate over time. Panels that are not calibrated are quicker to undergo deprecation, which greatly reduces visual quality.
Color Calibration
The acceptable range of variance in color wavelength between the LEDs in a display is 5nm. However, when your LED is manufactured, this value is much greater. Calibrating an LED for color is trickier than calibrating an LED for brightness, since there are thousands of pixels in each panel. Each pixel has three colors: red, green and blue which must be matched.
Color mixing is a technique used to calibrate an LED for its color. A small amount of one color is introduced to all the LEDs, which causes the color shift to be reduced. This creates a tighter color tolerance for all the LEDs. Since we have added a color to all the LEDs, the color gamut of the screen reduces. Therefore, it must be decided by the user to what extent they want to calibrate their screen for color.
Daily Maintenance Calibration
With age, an LED screen undergoes depreciation, as has been described above. The heat produced by LED bulbs damages the screen over time. This causes the panels to deteriorate in different ways. The spectral peaks of the LED are affected, which ultimately reduces the color and contrast of the screen. As chromaticity deteriorates, the overall image quality reduces. Regular maintenance of the LED, along with recalibration, can greatly increase its lifespan and reduce the effects of deterioration.
Temperature and power management are the most important factors when it comes to long-term LED performance. You must ensure that your LED screen has proper ventilation and cooling.
In order to avoid damage by power surges, install surge protection devices or a UPS. Ensure that hardware and software drivers are up to date. Brighter segments in an LED panel can overheat and damage the screen over time. Recalibration of LEDs helps protect the screen by maintaining uniform brightness levels.
While brightness of LEDs will decrease over time, regular maintenance and recalibration will help mitigate color inconsistencies and spectral loss. Since large scale LED screens are expensive to install, regular maintenance ensures a good return of investment. The effectiveness of recalibration greatly depends upon the quality of the LED; therefore, it is a good idea to invest in premium LED screens.
FAQs About LED screen calibration
Do old LED screens need to be recalibrated?
Yes, old LED screens need to be recalibrated to give better image quality and preserve uniformity. Over time, an LED suffers from depreciation, which causes a loss of color and brightness. Recalibration of an LED helps in mitigating the negative effects of LED depreciation. Regular maintenance and calibration of an LED screen can extend the lifespan of the screen substantially.
What tools and software are used for LED screen calibration?
LED calibration is a meticulous process which involves the use of several hardware and software tools. Colorimeters are special types of cameras that measure the color characteristics of the light emitted by displays. Spectrophotometers are used when precise information about the spectra of an LED is required. Light Meters are devices which measure the intensity of emitted light.
Calibration software is interfaced with hardware tools to analyze measured data and apply necessary adjustments to the LED. Novastar and Colorlight are examples of popular calibration software. Color Management Systems are another kind of software used in LED calibration. They ensure that color is displayed consistently, in spite of the device used to view the image.
