What is a dead pixel?

When you check for your smartphone, laptop, or computer screen or monitor specifications on the internet, some of the features you will see are the resolution of the screen and the pixels it has per inch. Pixels are dots on your screen that turn on or off to display everything on your device’s screen: information, video, images… Sometimes, a pixel can die, causing odd dots on your screen. But what is a dead pixel? And do you really understand what the term pixel means and what it means to have dead pixels on your device? If you don't, don’t worry because that is what this article is all about. We’re going to let you know what a dead pixel is and everything else you need to know about pixels: how pixels work, what it means for a pixel to be dead, what causes dead pixels, and how to detect the dead pixels. Just make sure you read this article untill the end.

What is a pixel?

In digital imaging, a pixel is the smallest addressable element of an image. If you tried to zoom any of your photos on your phone or PC, you will likely start seeing small squares, which may vary in number based on the quality of the device that was used to take the image. When it comes to displays, a pixel is also the smallest element of a display that is normally in the form of squares. You may find below a high-resolution image and a second low-resolution one. As you might guess, the second one corresponds to the black square on the first one.

Regular image

Zoomed-in image

If you closely look at one of your TVs at home while it is turned on, you will see very small squares on the screen. The combination of these small squares is what gives your TV the ability to display images and videos. In situations where the display has too many pixels per inch, you will likely not be able to see the individual Pixels – Apple calls this retina display.

This is most likely the case with most of the newer smartphones that have come through in recent years. Most of them have over 300 pixels per inch, which makes it almost impossible to see the individual Pixels with your naked eyes.

How do pixels work?

In any display, each pixel comprises three dots that can be called sub-pixels. Each of these dots is responsible for displaying one of the three primary colors, that are blue, green, and red. Based on what you want to display, the amount of color that is produced by each dot may vary. So, if you want to display an entirely red image, only the red sub-pixels shall emit light, which will then make the entire display to be red.

In another scenario, turning on the red and green subpixels will produce yellow, turning on all the three subpixels produces white, and turning on-off all of them shows black. That's how each pixel produces the desired color that when combined create the images that we see on the screen.

Change the intensity of each primary color to change the color of the pixel

Red

Blue

Green

In the case of videos, the change of colors for each pixel change in rapid succession at a speed that depends on the frames per second for the video being played on the display. The fact that the changes happen so fast is the reason it is hard to see with our naked eyes how each pixel changes color.

The number of pixels per inch that a display has will largely determine the quality of images and videos it will show. The smaller they are, the sharper the image will look! That is why the same video will appear different on an HD (1280 x 720 pixels) display and a Full HD (1920 x 1080 pixels) display.

When and why can a pixel die?

Noticing a dark, white or color-stuck spot on the screen, you probably have one or more dead pixels. The size of this dot depends on the number of pixels that are dead at that particular point. The more dead or stuck pixels you have, the larger the spot. So, in a situation where your display has very tiny pixels that can't be seen by the naked eye, you may not be able to see a dead pixel if there's only one.

Technically a pixel stops working when the transistor that powers it up fails. For those who may not know, a transistor refers to a small semiconductor device that is used to amplify or switch electrical power and electronic signals in electronic devices. Each of the pixels in any display is controlled by one transistor to give it signals of what colors to display and the intensity.

So, when the transistor is off, the pixel will neither have the power nor the signal of the colors to display. When no color is being displayed by the pixel, its default color will be black. Also note that a pixel can be stuck to any of the color combinations of the 3 primary colors.

Why are there dead pixels?

There are several causes of dead pixels, and some of these include the following:

Manufacturing defect

While manufacturing a display, errors can occur that could result in having one or more transistors of your display not working. Most of the companies that make displays always test each screen after manufacturing to make sure all its pixels work well. However, some of the tests are not effective enough to identify the dead pixels, especially if the display has too many pixels.

Physical damage

When you drop your phone or laptop on the ground, the force as a result of this drop could cause some of the pixels to get damaged. The display itself may continue working properly, but with some sections of the screen not displaying any content. If the dead pixels are very few, you may not even realize it, more so on smartphones that have over 300 pixels per inch. In some cases, the damages can gradually worsen, whereby the pixels fail one at a time until the point when the dark spot on your screen becomes visible.

Water damage

If your device gets splashes of water or when it gets immerged in water, one of the most vulnerable parts that could easily get messed up is its display more so if it is not water resistant. This is because when the transistors that power up you display pixels get in contact with water, they fail immediately. If your work or home environment involves getting in contact with water more often, just get yourself a water-resistant device.

Aging

Just like any other electronic device, displays age with time, which leads to the gradual failure of some pixels. For quality displays, this takes a lot of time to happen unless you handle your device carelessly during use. Most of the modern devices can be used for more than ten years without experiencing any issues with the display pixels. So, it will be a case of bad luck to find dead pixels due to age, but it does happen.

How can I know if one my pixels is dead?

For instance, when your phone falls, or when a "black" dust don't seem to come off you screen, you might be interested in knowing if all its pixels are still working normally.

Display one color at a time on your display..

What you should do is test displaying several colors on the entirety of your screen to see if you notice any odd-looking dots. Remember they can be dark, white, or any color that is a combination of the 3 primary colors (at their full intensity). Hence the pixel can be either "dead", or "stuck". We would recommend testing all the primary colors and all their combinations before you conclude that you don’t have any dead pixels.

Final thoughts on dead pixels

Getting dead pixels is quite a common problem that is caused by a couple of reasons that lead to the failure of transistors that power up these pixels. Like we have seen above, the commonest causes of dead pixels are; manufacturing defects and physical damages.

If you suspect any form of dead pixels on your device’s display, you can use our dead pixel testing tool. Check if your device's warranty takes dead pixels into account. Normally it takes a minimal number of dead pixel for the warranty to come into play... Good luck with your screens!