Why use a pattern instead of a photo
A photograph is full of detail, which hides small problems. A test pattern is the opposite: a simple, known image designed so that a particular fault is easy to see. A flat color makes uneven areas obvious. A smooth ramp makes steps visible. A grid makes distortion visible. Because you know what the image is supposed to look like, anything different is a sign of a problem with the screen, the settings, or the signal.
Test patterns can be shown from many sources: built-in screen menus, a computer, a media player, or an image file you open yourself. When you use one, make sure it is shown at the screen’s native resolution without scaling, since scaling alters fine details. The article on native resolution explains why scaled images look soft.
Solid colors
Full-screen black, white, gray, red, green and blue are the simplest patterns.
- Black shows backlight glow and bleed, and any pixels stuck on.
- White shows pixels stuck off, dust, marks and tints.
- Mid-gray shows cloudy or uneven areas most clearly.
- Red, green and blue show whether one color is weak or uneven, and make stuck pixels of those colors stand out.
These are the first tests to run. They are covered in more detail in the articles on dead pixels and on screen uniformity testing.
Gradients and banding
A smooth gradient from black to white should look continuous. When it shows visible stripes or steps, the effect is called banding. Banding can come from the content, the signal path, or the screen. With 8 bits per color channel, there are 256 levels from black to white in each channel, and a ramp across a wide area can show visible steps in some conditions. Screens and software sometimes add tiny noise, called dithering, to hide steps. The article on bit depth and why gradients show banding explains the mechanism.
To test, display a gray ramp and look for steps. A color ramp can show whether one channel has more steps than the others. If banding appears in the pattern but not in other sources, the problem may lie with the signal, driver or settings, not the screen. Try a different cable or output mode to check, as the article on display connections suggests.
Gray steps and clipping
A series of gray patches from black to white, shown side by side, tests whether the screen distinguishes each level.
- Black clipping. If the darkest few patches look identical to pure black, shadow detail is being crushed. This can be caused by a brightness setting that is too low, a wrong signal range, or a gamma curve that is too steep.
- White clipping. If the lightest few patches merge into pure white, highlights are being lost. A contrast setting that is too high is a common cause.
- Signal range mismatch. Video signals can use a limited range, where black and white are not at the extremes of the scale, or a full range. If the source and the screen disagree, blacks look gray or are crushed. A mismatch of this kind is a common and fixable cause of poor-looking images.
Seeing every step distinct from its neighbors suggests the settings are reasonable. These patterns tie in with the brightness checks in the article on brightness and contrast and the gamma curve explained in the article on gamma and tone response.
Checkerboards and contrast
A checkerboard of black and white squares tests contrast with both extremes in the same image. On some screens, bright areas affect dark ones nearby. LCDs with local dimming can show a glow around bright squares on a dark background, and some panels dim the overall image when a lot of white is shown. A full black or full white field alone would not show this. The article on mini LED backlights and local dimming goes into the underlying design.
Lines, grids and sharpness
Fine patterns test sharpness and geometry.
- Alternating one-pixel black and white lines or checks. On a screen at native resolution, with no sharpening, these should look crisp and regular. Blurring, moire patterns or uneven lines suggest scaling, a sharpening filter, or a signal problem.
- Text at small sizes. Reading small text reveals sharpness in a practical way.
- A grid or crosshatch. Lines should be straight and evenly spaced. On a flat panel, bent lines suggest a scaling or processing issue, and they are more of a concern on curved or projected displays.
- Edge patterns. A thin border on each edge shows whether the image fits the screen or is being cropped by overscan, a setting on some TVs that enlarges the image slightly.
A sharpness setting that is too high adds bright outlines around edges. A line pattern with a halo next to each line is a sign of this. Setting it to a neutral position is usually appropriate for testing, and the article on picture modes explains why modes affect results.
Color bars and skin-tone patches
Color bar patterns display the primary and secondary colors in a fixed sequence. They help check that colors are in the right order and look correct, and that no channel is swapped or missing. Patches of common colors, including natural tints, give a rough sense of whether colors look plausible, although judging accuracy needs a reference, as the article on color accuracy describes.
Motion patterns
Moving patterns show how the screen handles movement. A moving object on a plain background reveals trails and blur, and a moving row of lines can show whether the screen keeps details sharp in motion. The motion blur article describes these in more depth.
Using patterns well
A few habits make patterns more useful:
- Use the right conditions. A dim room and a warmed-up screen make faint issues easier to see.
- Turn off automatic features such as dynamic contrast and auto brightness while testing.
- Test at native resolution with no scaling or sharpening.
- Change one thing at a time, so you know which setting caused which change.
- Know your pattern’s purpose. If a pattern is not described, you may misread it.
A pattern tells you that something is off, not always why. The fault might be in the screen, a cable, the software, or a picture mode. Moving from simple to complex, and swapping one element at a time, usually narrows it down. Patterns are a good first check, and they complement but do not replace measurement where precision is needed.