Red screen
A full screen of pure red, driving the red sub-pixel to maximum while green and blue stay completely off.
Esc to exit · arrow keys to change · H hides the controls
Dimming changes what is sent to the panel, so this is no longer an exact colour value. Return the slider to 100% before judging anything.
What a red screen is for
Isolating one sub-pixel at a time
Each pixel on a colour display is built from separate red, green and blue elements. On white all three are lit, so a single failed element only tints the pixel slightly and is easy to miss. A pure red field switches off green and blue entirely, which means every lit dot you can see is a red element doing its job. Anything black on this field is a red element that has failed. This is why a proper pixel check runs the three primaries individually rather than stopping at black and white, and it is the reason the dead pixel test cycles through all of them in sequence.
What red tells you that white cannot
Look for small black dots, and for dots that look darker or duller than the field around them without being fully black. A partial failure often shows as a dimmer red rather than an absence of red. Because red is a fairly dark primary to the eye, subtle differences in brightness across the field stand out more than they would on white, which also makes this a reasonable quick check for patchy uniformity.
Checking red clipping and saturation
Fully saturated red is where oversaturated picture modes give themselves away. If your display is in a vivid or dynamic preset, red often gets pushed until detail in red areas collapses into a flat block. Switch between this page and the greyscale ramp with your picture mode set to standard and then to vivid, and the difference in how red behaves is usually obvious.
Preserving night vision
Red light disturbs dark-adapted vision far less than white or blue light does, which is why astronomers, darkroom workers and night-shift crews use red lamps. A red full screen at low brightness makes a serviceable improvised red light when you need to find something in the dark without resetting your eyes.
How to run this test
- Run this after white and black, as the first of the three primary fields.
- Go full screen and get close enough to see the field clearly without straining.
- Look for black dots, which are failed red elements, and for dots that are dimmer than the field around them.
- Sweep the whole panel once, then repeat on green and blue so all three elements are covered.
What a problem looks like
- Black dots on red
- A red sub-pixel that has failed. The same pixel will still light on green and blue, so it will not look fully dead on a white field, which is exactly why this check matters.
- Patchy brightness
- Visible variation in how bright the red is across the screen points at panel uniformity rather than a pixel fault. Confirm it on a grey field, where mura shows more clearly.
What to do next
If something looks wrong, check it again in a normally lit room and from straight on, then check whether it appears on a second device. If it only happens on this screen and you are still inside the return window, that is the time to contact the retailer.
Questions people actually ask
Why check red separately if I have already checked white?
A white field lights all three sub-pixels, so one failed element only slightly tints the pixel and is easy to overlook. On a red field, green and blue are off entirely, so a failed red element appears as an unmistakable black dot.
My red screen looks orange. Is something wrong?
Check whether a warm-light feature such as Night Shift or Night Light is running, since those shift everything towards orange. A wide-gamut display in an uncalibrated mode can also render sRGB red more intensely than intended. Neither is a panel fault.
Does a red screen help with eye strain at night?
Red light at low brightness interferes with dark adaptation less than blue-heavy white light, which is why red lighting is standard in observatories. It is a reasonable improvised night light, but it is not a treatment for eye strain, and screen brightness matters more than colour.