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When it comes to dealing with monitor uniformity issues, there are a few relatively easy ways to test for and correct the “dirty screen effect” that sometimes happens on LCD screens and other top computer monitors on the market.
Other issues that may arise with displays are black sidebars on the edge of the screen and screen flickering on Windows 10. These may not always be present, so it’s good to test your display regularly, especially after working on monitor uniformity.
Luminance uniformity, sometimes divided into black, gray, and white uniformity, refers to the evenness of the light levels at every point on the screen. So when given a dark scene, an all-white or solid color test picture, the difference in illumination averaged across the screen. Most gray and white uniformity issues arise from minute differences in the light output of individual diodes in an LCD screen’s backlight array. This pixel by pixel deviation can vary between individual units of the same model. Read on to learn how to fix this common display problem.
Some dirty screen effects are caused by slight variances in manufacturing or handling of the individual product. In LCD screens, any unevenness in the pressure of the layered LCD panels may cause some areas to diffuse light differently from others, resulting in people finding the appearance of their display panel to lack evenness of colors. OLED screens can suffer from luminance non-uniformity due to any variance in the output of individual diodes, though most of the newer AMOLED screens perform well on uniformity tests.
Older monitors can also have brightness uniformity issues due to stuck pixels. Usually, this happens because the higher-energy pixels blue pixels burn out faster.
LCD screens typically have more issues with dirty screen effect than do OLEDs, though an OLED monitor may have issues may have a lack of uniformity due to different output among individual pixels. This is most noticeable when looking at a white screen. Color uniformity issues can also appear in OLED monitors for this reason, but some displays offer a uniformity compensation feature. On LED monitors, luminance uniformity problems are most often visible in the corners.
You can test for poor uniformity on any monitor by showing an all-white, all-black, or solid color image. Then using an external camera and image processing software, you can see the color values and luminance values of each pixel in the resulting image. Alternatively, there are software solutions that come with image files to make this process easier. You can then upload your photos and the software will provide a value for color uniformity, white or black uniformity. The difference in color values across the picture is given in Delta E. The lower this number, the more uniform color reproduction across the entire screen.
To test gray uniformity issues, there is standard 5% gray (almost white) and 50% gray images you can use. A lack of uniformity will show up as a noticeable difference in brightness, typically more than one standard deviation apart in color value or luminosity. If you’re experiencing lag time, you might also be interested in testing your monitor for input lag.
Occasionally a “dirty screen effect,” is just, well, literally a dirty screen. You’ll want to pick up a quality LCD screen cleaning kit consisting of a non-abrasive microfiber cloth and monitor cleaner. Never clean use water or chemical products such as countertop glass cleaner or rubbing alcohol on your monitor screen. Many all-purpose cleaners with ammonia, citric acid, or bleach can permanently degrade the screen.
Tip: Never clean use water or chemical products such as countertop glass cleaner or rubbing alcohol on your monitor screen
If the factory calibration of your monitor is off in the color settings, you can often notice a color cast that looks like a dirty screen effect. Luckily, this dirty screen effect is easier to fix than luminance uniformity issues due to hardware variance and the ability to improve color accuracy and evenness of color reproduction through modifying the settings. Make sure the color presets you’re using on your computer match the color matrix of the monitor.
Warning: Make sure the color presets you’re using on your computer match the color matrix of the monitor
Some high-end monitors such as the X-Rite i1 Display Pro offer advanced calibration abilities, including a digital uniformity equalizer function. Monitors used for professional editing and color correction need to have measurable and consistent color values, so these gamut monitors offer software with a uniformity correction function that lets you fine-tune their uniformity compensation, ensuring minimal color variation across the screen. If you’re also dealing with image burns, you’ll want to learn how to fix image retention on your monitor as well.
For a consumer-grade monitor in 2020, a typical value of uniformity is 2.5% variance or less in the squared difference in luminosity across pixels.
The median gamma decoding value across the color range for the sRGB color encoding is approximately 2.2
LCD Backlight Grey Uniformity Test – YouTube www.youtube.com › watch
“Chapter 12. Dynamic Range – Linearity and Gamma”
“Get the best display on your monitor – Calibrate your display”
Friedl, Jeffrey. “Digital-Image Color Spaces, Page 2: Test Images”. Retrieved 2018-12-10. See For Yourself The Effects of Misinterpreted Color Data
The dirty screen effect is sometimes due to dust or dirt on the screen, in which case it's easy to fix. Often, however, some lack of uniformity is inherent to the hardware itself. This can vary between units of the same product, so if you can't tolerate it, you may want to return yours and try your luck with a different unit.
Typically, a standard set of images are displayed, called the 5% gray test.
It’s a noticeable irregularity in color or brightness that most typically shows up in nearly all-white or solid color images. Sometimes non-uniformity can show up in mostly-black pictures as well. It can look like a haze or blur, or like darker patches on an otherwise white image.