Watching something on the television after a long day at work is one of the most popular ways to unwind, and when you are trying to relax, there are few things more annoying than a TV that is having some issues. One of these issues might be that your screen keeps dimming itself, making for an unpleasant TV watching experience. Luckily, this is quite easy to fix, and you don’t even need to get up from the couch.

To troubleshoot a TV that keeps dimming, you will need to make some adjustments to the settings, including picture settings, dynamic contrast, ambient light settings as well as energy-saving settings. You may also have to replace a broken light in the lighting panel if it is broken.

Throughout this article, you will learn the following about troubleshooting your TV:

  • How TV screens work to produce light and color.
  • Why your TV screen keeps automatically dimming.
  • How to stop it from automatically dimming.

How Do TV Screens Work to Produce Light and Color?

Televisions are complex machines with a lot of intricate parts that allow them to produce the images we see on their screens. There are also a few different types of televisions out there, and they all work in slightly different ways. We’re going to take a look at how each of the different types of televisions work.

CRT Screens

The CRT (short for cathode-ray tube) TV was one of the earliest versions of the kind of television systems we use today, well used to. It was first patented in 1929 by a Russian engineer called Vladimir Zworykin.

Cathode-ray tube televisions receive a signal through an antenna and then split it into an audio signal and a video signal. The audio signal is transmitted to a speaker to create the sound you hear. The video signal is sent to something called an electron gun circuit.

The electron gun circuit separates the video signal into red, green, and blue signals, each of which operates an electron gun. This then fires a stream of electrons down a cathode ray tube toward the screen. On their way, the electrons move through an electromagnet coil, which directs them to move across the screen in a sweeping motion.

The screen is covered in very small dots of phosphor, which light up when the electron beam hits them. The beam of electrons is passed through a grid made of holes that allows it to only hit and light up certain phosphor dots, creating a picture on the screen.

Plasma Screens

Plasma screens were popular at one time, but they are not being produced anymore. This is partly because of how expensive it is to make them and partly because competing technologies have become better and more popular.

Thus, we won’t spend too much time on plasma technology, but in a nutshell, plasma screens are made up of tiny cells containing phosphor, xenon (gas), and neon (gas).

The electric current entering the TV excites the xenon and neon atoms, transforming into a plasma state. When they are in this state, the atoms release ultraviolet light, absorbed by the phosphor in the cells, and then transformed into visible light to create a picture on-screen.

LCD Screens

LCD, which stands for liquid crystal display, screens are made of three main components: the liquid crystal display, after which they are named, the light source put behind the display, and a diffuser that is put between these two layers.

The liquid crystal display is used as a filter to block the light going to certain pixels of the screen. The crystals twist and untwist to either block or let light through. This is controlled by administering an electric current to the display. This twisting of the liquid crystal cells creates the light, dark, and colors that ultimately make up the picture you see on screen.

The light source in an LCD television is called a backlight, and there are two different types. The first is called CCFL (cold-cathode fluorescent lamp) backlight. This means that several tubes of light are put horizontally behind the LCD, which serve as a light source.

The second type of backlight uses LED lights, which we will go over next.

LED Screens

LED (light-emitting diode) TV screens work in the same way as LCD screens because that’s essentially what they are. The only difference between the two is that traditional LCD screens have a CCFL backlight, and LED screens use LED bulbs as a backlight.

So, technically speaking, the only difference between an LCD and an LED screen is how the screen is lit. The quality and colors are all still the same.

However, LEDs have the advantage of being more energy-efficient than fluorescent lamps in an LCD screen, which is why they have become more popular in recent years.

There are three ways that the LEDs in an LED TV’s light source can be arranged, and each produces a different outcome.

Full Array

Full array backlight is usually only found in higher-end TV models since it uses more LEDs to light the screen, making it more costly to manufacture.

Full array screens have LEDs spread out uniformly behind the display panel. This means that the light source will be even, the picture quality will be great, and ensure that local dimming works.


Edge-lit arrangements are what you will find in most LED TVs on the market today. The LEDs are placed at the very edges of the screen. Sometimes on either side, sometimes all around, and sometimes only on the bottom.

This is a very cost-effective way of lighting a screen and allows for the screen itself to be slimmer, but will often produce unevenly lit images.


Direct-lit arrangements are similar to the full array arrangement in that the LEDs are distributed evenly behind the display. However, there aren’t as many LEDs used for direct-lit arrangements.

These types of screens are usually the thickest because of the space needed for the LEDs to diffuse the light over the entire screen. You can also not control the LEDs individually as you are with full array screens, meaning that the picture might not have as much contrast.

OLED Screens

OLED, which stands for organic light-emitting diode, TV screens use technology similar to standard LED screens except that they are made from organic plastics, mostly carbon.

You can also make use of local dimming, which makes for better contrast and gives you better picture quality. OLED screens have arguably the best picture quality there is. They can also fit into very thin frames, making them the go-to option for anyone who doesn’t want a big, clunky TV standing around.

However, they are on the pricier side of things, but their picture quality and energy efficiency make them worth the money.

QLED Screens

QLED, also sometimes referred to as quantum dot display, is the name Samsung has given their newer TVs.

They use the same LCDs and LEDs like the other types of LED screens, but in between the two layers, there is another layer of quantum dot particles that create a photoelectric effect and transform the blue light from the LEDs into more pure basic colors (red, green and blue). This means that QLED screens often have the most saturated colors.

MicroLED Screens

MicroLED is a technology that has been around for some time but has never been commercially produced. It is said to take the best characteristics of the LED and OLED technologies and create a new and impressive technology that will far surpass other technologies.

A couple of companies are rumored to be working on microLED TVs, but none have actually released one yet.

Why Does Your TV Keep Dimming Itself?

Before we discuss how to stop your TV from dimming itself, we need to understand why it is doing so.

You Connected It to an External Input

Some people have found that when they connect their TV to external input, like a PC, the TV screen dims down a few seconds after it was connected.

This may be because there is a problem with the external adapter, your PC monitor is set to auto-dim when connected to an external display, or your PC is set on a power-saving mode.

However, when you change the input mode on your TV, all display settings reset back to their original settings, which means that changing the display output settings in one input mode doesn’t carry over to the other input modes.

Global Dimming

Global dimming happens when the display panel processor reduces the power supply to the light source when a dark scene or picture is being displayed to produce deeper blacks.

This happens most often in LCD TVs that are lit using CCFLs, meaning that there is no way for the backlight to dim in only one area, as is possible with LED backlight. Instead, the whole screen dims down at once.

Dynamic Contrast

Dynamic contrast is a feature that was added to newer TVs to increase the contrast of the picture being shown on screen and make the picture quality look better. This is dimming and brightening the backlight to make blacks deeper in dark scenes and whites brighter in light scenes, respectively. Essentially, it changes the brightness of the screen, depending on the contents of what you are watching.

Ambient Light Detection or Eco Sensor

Ambient light detection, or eco sensor as it is called in older TVs, is a technology that detects the amount of light in the room that the TV is in and then adjusts the backlight brightness accordingly.

This is a feature that was added to help reduce the amount of electricity TVs use and give you a better viewing experience based on your surroundings.

Image Dimming Over Time to Prevent Image Retention

Sometimes TVs can experience something called image retention, which happens when there is a static object or image displayed on a screen for an extended period.

Technology has been developed to stop this from happening and involves dimming the area where the object is being displayed to stop the screen from retaining the image or an outline of it, after it is no longer being displayed.

This can often lead to some parts or even all of the TV’s screen being dimmer than other parts and may be annoying to some people.

Broken Lighting Panels

If you notice dimmed spots on your TV screen that won’t go away, no matter which settings you change, chances are that one or more of the bulbs in the backlight have blown. This can happen occasionally and means that you will need to get a replacement bulb to fix the issue.

How to Stop Your TV From Automatically Dimming

Sometimes, the features put into our devices nowadays meant to make them smarter often end up doing the exact opposite. This seems to be especially true for TVs made by LG, Samsung, and Sony. However, it might be a problem across all TVs, and the customers of those companies just happen to be the most vocal about their issues.

Luckily, there are ways to fix these issues without having to spend a lot of money hiring an expert to do it for you. All you need to do is a quick search on the Internet, and you will likely be able to find the solution to your problems. Here are some solutions to one of the most common problems, automatic screen dimming.

Fixing Your Settings

Most of the solutions to the possible reasons why your TV keeps dimming can be found in your TV’s settings. So let’s take a look at which settings you can change to fix this issue.

External Input Settings

When switching between input modes on your TV, the brightness of your screen will change depending on how you have adjusted your settings.

To fix this issue, you will need to change your TV’s input mode to all of the different modes you use most often or go through them one by one and change the setting on each of them individually. You can either adjust the brightness manually or turn off any of the eco sensor or ambient light detection settings that most TVs come equipped with these days.

This is not a very cumbersome task, but once you’ve changed the settings, they’ll stay that way, and you will immediately notice the difference.

Dynamic Contrast

To fix the issue of dynamic contrast, you will need to turn this feature off in your TV’s settings. You can usually find this feature in the picture setting or advanced picture settings where you will be able to switch it off. You can adjust the intensity on some TV models, so you might want to opt for putting it on a low setting instead of turning it off completely.

This will fix the issue of automatic dimming and will also give a more natural, less intense image on-screen.

Ambient Light Detection or Eco Sensor

Turning off your TV’s ambient light detection, eco sensor, or any automatic brightness setting, for that matter, will give you more consistent brightness while watching something but will also increase your energy usage.

To turn this setting off, first, you will need to locate it. Various television brands will have this setting in different places, but usually, it can be found somewhere under the backlight or picture settings or the energy-saving menu. Also, make sure to take your picture mode off of automatic, as this also sometimes changes your screen’s brightness.

If you want to watch a quick video on how to fix your TV’s dimming issues, you can do so here:

YouTube video

However, there may be other things causing your TV’s screen to dim, so let’s take a look at them now.

Broken Lighting Panel or Bulb

Replacing a broken light panel or bulb is not something we recommend you do on your own. It is best to hire an electrician or repair person to come in and fix it for you. They’ll also be able to assess the damage better and will be able to tell you whether it is worth repairing or whether you should just buy a new TV altogether.

Global Dimming

Global dimming is a problem that CCFL lighting panels encounter quite often. Unfortunately, there is no way to fix this problem, as there is no way to dim only a part of a fluorescent light tube without breaking the bulb itself.

Image Retention Prevention

This technology is built into your television’s firmware, and there is no readily available way to fix or change it at the moment.


Televisions are great devices, and their technologies are always advancing to make them better. However, that doesn’t mean that you won’t run into the occasional issue with them.

If your TV screen keeps dimming, you can change several settings, including dynamic contrast, ambient light detection, and input mode settings to fix this issue. And if all else fails, call in an expert to help you solve this problem.