Conclusion: display single colors sequentially in full screen and record position and color
Clean the screen, move the window to the target monitor, and enter full screen. Display black, white, red, green, blue, and gray in order, recording persistent dots and broad tonal variations separately.
| order | What to Check | Points of judgment |
|---|---|---|
| 1 | Preparation | Clean the surface and move to the target monitor |
| 2 | black | White/RGB bright points and brightness at screen edges |
| 3 | white | Dark spots, dirt, broad dark areas |
| 4 | RGB | Subpixel symptoms by color |
| 5 | gray | Broad unevenness in color and brightness |
Separate symptoms that are easy to spot by background color
It is difficult to distinguish between bright spots, dark spots, subpixels, dirt, and color unevenness with just one background color, so switch between black, white, RGB, and gray under the same conditions.
| Display | easy to find | way of seeing |
|---|---|---|
| black | Constantly lit white, red, green, and blue dots, brightness at the edge of the screen | Distinguish and observe bright point candidates, IPS Glow, and backlight leakage |
| white | Black spots, dirt, large dark areas, uneven brightness | Isolate dark spot candidates, surface dust, and brightness unevenness |
| red, green, blue | Dots or missing colors that do not match the background color | Compare which RGB subpixel causes symptoms |
| 25%, 50%, and 75% gray | Band-like/cloud-like shading, Dirty Screen Effect | Visually compare uniformity. Not a numerical measurement |
| low contrast gradation | Steps in gradation, local differences in color and brightness | View trends using browser-generated patterns instead of compressed images |
We do not recommend methods that forcefully press, rub, or apply shock to the screen as this may damage the panel. When cleaning surfaces, turn off the power and follow the product instructions.
Narrow down the cause candidates based on the range of symptoms and reproduction conditions
| Symptoms observed | Main candidates | Next check |
|---|---|---|
| black with only one bright spot | Bright/stuck pixel or subpixel candidate | Check the same position on the RGB screen |
| White with only one dark spot | Dark/dead pixel candidates, dust and dirt | Turn off the screen, clean the surface and check again |
| The appearance of the dots changes depending on the color | Candidates for fixing/turning off some subpixels | Compare and record red, green, and blue in order |
| Bright/dark over a wide area | Brightness unevenness, viewing angle, light leakage, DSE, etc. | Compare the front distance, ambient lighting, and brightness. |
| Also visible in screenshots | Possibilities on the OS/GPU/application/image data side | Open the image on another device to isolate the display path |
| Not visible in screenshot | Clues for panel/connection/display settings | Reconfirm with monochrome screen and built-in monitor diagnostics |
- A bright pixel/subpixel that remains on
- A dark pixel/subpixel that remains off
- Surface dust, dirt, and protective film
- Appearance based on viewing angle and ambient light
- Nonuniform color and brightness across the entire panel
Treat a small point separately from cloud-like or band-like unevenness. For points, check multiple colors; for unevenness, check whether it also reproduces in gray and ordinary images.
Whether it reproduces at the same screen coordinates is important. If the position changes when you move your gaze or the window, also check surface reflections and viewing angle.
Visual results are the key to narrowing down the cause. It does not automatically diagnose pixel defects, panel failures, IPS glow, backlight bleed, and burn-in based on appearance alone.
Range that can be confirmed with dot dropout/color unevenness test
| Item | What you can do with current tools | constraints |
|---|---|---|
| Solid color | Black, white, RGB, CMY, yellow, 3-level gray, any color | Do not automatically determine pixel defects and uniformity |
| pattern | checker, 1px checker, vertical and horizontal 1px lines, gray/RGB gradient, alignment, low contrast | There is no guarantee that there will always be a 1:1 correspondence with the native pixels of the actual panel. |
| Actions | Full screen, forward/backward movement, automatic switching, keyboard, mouse, touch | Browser needs to support/allow Fullscreen API |
| Display aid | Hide the operation display and cursor after a certain period of time in full screen | No full control over browser or OS overlays |
| monitor information | CSS resolution, estimated display pixels from DPR, color depth, orientation | It is not the panel native resolution or colorimetric value itself. |
| privacy | Generate pattern in browser and do not send screen data | We do not perform warranty judgments, repair requests, color measurements, or calibrations. |
Browser zoom 100% is not required to check single colors. On the other hand, 1px checker and 1px line are affected by browser zoom, OS scaling, DPR, and panel scaling, so they do not assume a one-to-one correspondence with native pixels.
Gray and low contrast patterns are useful for visually locating uneven color and brightness. It is not a function to numerically measure Delta E, brightness, color temperature, etc., or to create an ICC profile and perform color calibration.
Confirmation steps to reduce oversight and false positives
- 1. Safely clean the screen surface with a soft cloth.
- 2. Search for bright points on black from edge to edge.
- 3. Search for dark points and broad dark areas on white.
- 4. Compare the same coordinates in red, green, and blue.
- 5. Check broad unevenness using gray and low-contrast patterns.
- 6. Record the background color, position, count, and conditions.
Record the monitor you check, viewing distance, viewing angle, brightness, and ambient lighting. Don't change multiple conditions at once and compare whether the symptoms recur in the same location.
Check official information and product-specific terms
Pixel policy, inspection distance, ambient lighting, replacement conditions, and panel protection functions vary depending on manufacturer, model, sales region, store of purchase, and warranty plan. Please check the following primary information and the manual/warranty regulations for the target product.
| Confirmation destination | URL | What you will see in this article |
|---|---|---|
| Dell「Display Pixel Guidelines」 | https://www.dell.com/support/kbdoc/en-us/000126004/dell-display-pixel-guidelines | Structure of pixel/subpixel, appearance of bright and dark spots, pixel policy by product |
| Dell “OLED Monitor Bright/Dark Pixel confirmed” | https://www.dell.com/support/kbdoc/en-in/000199168/how-to-inspect-for-a-bright-or-dark-pixel-on-a-alienware-or-dell-oled-monitor | Visual confirmation using RGB, black, and white monochrome screens |
| Dell「Troubleshooting Light Leakage」 | https://www.dell.com/support/kbdoc/en-us/000132299/troubleshooting-light-leakage-bleeding-on-a-lcd-monitor-or-notebook-lcd-screen | Use a dark background, ambient lighting, brightness, and comparisons with the same model to isolate light leakage |
| Dell「IPS Glow and Light Leakage」 | https://www.dell.com/support/kbdoc/en-us/000318297/how-to-distinguish-ips-glow-and-light-leakage-in-a-dell-monitor | The difference between IPS glow, which changes with viewing angle and distance, and relatively fixed light leakage |
| MDN「Fullscreen API Guide」 | https://developer.mozilla.org/en-US/docs/Web/API/Fullscreen_API/Guide | requestFullscreen, exit method, fullscreenchange, browser difference |
| MDN「Element.requestFullscreen()」 | https://developer.mozilla.org/en-US/docs/Web/API/Element/requestFullscreen | User operations, promise rejection, response conditions |
Record the results and proceed to confirm warranty/return/repair
Record the color reproduced in the same position, appearance, quantity, date of purchase, model number, and serial number. If necessary, take pictures from an external camera under normal lighting and leave the symptoms behind instead of relying solely on screen shots.
| Recorded items | Recording example | Usage |
|---|---|---|
| position | Approximately 120px from the top left, equivalent to 80px from the top | Check if it reappears in the same location |
| Background color | Red on black, black on white, unnoticeable on green | Explanation of bright/dark/subpixel candidates |
| conditions | Front 60cm, normal lighting, brightness 50% | Distinguishing from how you see in a dark room or only at extreme viewing angles |
| Product information | model, serial, date of purchase, store | Identify the target warranty policy |
Rather than deciding whether or not to exchange items based on a uniform number of items, we check the latest policy for the target model and region of purchase. When contacting the warranty center, please briefly explain the confirmation conditions and reproduced colors.
Example: A single point that appears red on black and dark on green
If the same position appears red over black and does not match its surroundings on a green background, it can indicate a partial subpixel state.
Check appearance on white, red, and blue as well, exclude dirt, then record results for each background color.
- Record the position in black.
- Display white and RGB in sequence.
- Turn off the screen and inspect the surface.
- Report reproduced colors to the warranty contact.
Do not conclude that a visible appearance alone requires repair; check the product-specific pixel policy.
Frequently asked questions
- Can dead pixels be checked with only a black screen?
- Black makes bright dots easy to find but dark dots difficult to see, so also check white and RGB.
- Can color unevenness be measured numerically?
- This tool is a visual pattern. Quantitative evaluation requires a compatible colorimeter and software.
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