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What is Monitor Contrast Ratio? – Definitive Guide

There is absolutely no doubt that contrast ratio is one of the most critical features in display devices.

In many ways, contrast ratio determines the quality of the display device since it is the direct reflection of how well it produces the pictures.

While this may not be the first feature that the store owner talks to you about, it is certainly one of the most important one to take note off as an informed buyer.

You may often get too distracted by the flamboyant features of a TV or a monitor like a curved form factor, ultra high resolution or a large screen, while completely forgetting about features like Contrast Ratio that actually relate to the picture production.

As an informed customer, you must make sure that you inquire about it properly.

Also, there are plenty of gimmicky terms and numbers that you may come across with relation to the contrast ratio. Numbers like INFINITY contrast ratio or 1,000,000:1 DCR etc are all meaningless to most extent.

In this article, we will have a look at the “what is monitor contrast ratio” in detail and also differentiate gimmicks from real features.

If you want to go straight to Buyer’s Guide Below then Click Here.

However, if you want some in-depth knowledge, we suggest you read the article in its entirety.

Note: This article will assume you know nothing about Contrast Ratio. Therefore this is a beginners’ guide.

Also Read: What is Monitor Refresh Rate?

Definition of Monitor Contrast Ratio

Let us see what our beloved Wikipedia has to say about the definition of contrast ratio:

“The contrast ratio is a property of a display system, defined as the ratio of the luminance of the brightest color (white) to that of the darkest color (black) that the system is capable of producing.

If this gives you a headache, don’t worry. Wikipedia tends to be too technical for an average person like you and me.

To put it in simpler terms, contrast ratio is the difference between the brightest image and the darkest image that a screen can produce.

A typical number of 1000:1 contrast ratio on a monitor means that a pixel can be a 1000 times brighter than its dimmest state. 

If this definition also seems too obscure, then I promise you that by the end of this article, you will understand exactly what contrast ratio entails as well as its various jargon and nuances.

Lets begin by breaking the definition down first and start out by understanding what luminance means.

What is Luminance?

1 - candles v9

The candle with 2 Nits is emitting more intensely as compared to the candle with 1 Nit

Luminance, in physics, is the measure of how intensely the light is emitted, passed, or reflected from an object per unit area. This is measured in candela per square meter abbreviated as cd/m2 – this in turn is generally shortened to the term called nits.

If you have read the datasheet for PC monitors recently, you may have come across the brightness specification with an average value between 250-350 nits.

That basically shows the intensity of the light EMITTED from the many LED lights at the back of your monitor.

Now that you know what luminance is, let us define what is color contrast – its not the same as Contrast Ratio.

What is Color Contrast?

In the most simplest term, Color Contrast is the difference between two colors.

Color Contrast is an important consideration when a director creates a film scene, a designer creates a graphics or when a photographer takes a photo.

Furthermore, two shades of color may seem the same visually, but may hold an entirely different value in a color space. Therefore, even if they seem the same, they have a Color Contrast.

There are many types of Color Contrasts and this information is used by designers and content creators to make appealing images, photos or interfaces.

Color Contrast including Hue Contrast, Tint and Shade contrast, Saturation contrast are all terms used by content and graphics designers.

So how does Color Contrast relate with the Contrast Ratio.

Color Contrast is the function of the art piece, the movie scene or the graphic that you have just produced. Contrast Ratio is the function of your display device and its ability to do justice to the Color Contrast of your creations.

IT WON’T MATTER HOW BEAUTIFUL THE COLOR CONTRAST OF THE PHOTO YOU EDITED, OR THE GRAPHICS YOU DESIGNED, OR THE MOVIE YOU ARE WATCHING IS IF THE DEVICE THAT YOU ARE VIEWING IT ON DOES NOT HAVE A GOOD CONTRAST RATIO.

What is Contrast Ratio (Luminance Contrast)?

As mentioned earlier, Contrast Ratio is a function of the display device like TV or a monitor.

A TV or a monitor with a bad Contrast Ratio will put all your efforts of creating and choosing the right Color Contrast for your masterpiece movie or graphics to waste.

Contrast Ratio, in physics term, in effect is the Luminance Contrast.

The measurement of Contrast Ratio, aka Luminance Contrast, has a direct relation with the quality of the display product.

It is the number that we get when we take White Luminance measurement (Brightest Light Emitted by the Screen) and divide it by Black Luminanance measurement (Darkest Spot Created on the Screen).

Mathematically,

Contrast Ratio Equation

Visually,

Contrast Ratio Main v2

A display device with a bad contrast ratio (Right) cannot maintain proper black levels. (The images are exaggerated to show the point). Image Source: Geoffrey Morrison/CNET

What is Ambient Contrast?

Ambient Contrast is measured when a display device is subjected to ambient light.

Basically, it is the measurement of how well a display can produce darker images when viewed with ambient light conditions.

This can vary tremendously depending upon the ambient light condition around you. For example, the Ambient Contrast measurement of a device under direct sunlight would be significantly different as compared to its measurement in a normally lit room.

While the Ambient Contrast isn’t something that is specified on the display spec sheet, there are technologies and measures employed to improve the Ambient Contrast of the device.

Glossy vs Matte

Matte Surface have a better Ambient Contrast as compared to Glossy Surfaces

This includes anti-reflection coatings such as Matte Surface or the ability of the device to automatically ramp up the backlight brightness when in brighter environments using sensors.

TV or monitor specsheets do specifiy the surface coating used. They will specifically mention whether the display device has a Matte Surface or a Glossy Surface.

Glossy Surface, found usually on touchscreen devices, performs very poorly in brightly lit areas or under sunlight since it does not prevent the ambient light from illuminating the darker areas.

Glossy Surfaces do have their uses however, read more in the Buyer’s Guide section.

Contrast Ratio Measuring Techniques (and MANIPULATIONS)

This section uses the information and is also inspired by the following video: Contrast Ratio Explained by Barco TV.

Let us learn about how Contrast Ratio is measured and why it can be so MISLEADING depending on the technique being used.

Issues with Measuring Contrast Ratio

There is no such thing as a perfect measurement standard for Contrast Ratio.

Besides the technique being used, there are plenty of factors that can affect the Contrast Ratio at a given time.

For starters, there is the issue of ambient light. In other words, the measurements of a display contrast ratio can change depending upon how lit the room is.

Near perfect dark conditions can only be achieved in labs and even then there can be room for error.

You can paint your entire lab room in Vantablack so that no light is emitted off the walls of your room as well, however, that too wouldn’t be perfect since variables like Stray Light or Backlight Bleeding can illuminate the unintended dark pixels (more on this below).

In short, there is no standardized method of testing the Contrast Ratio which is what results in confusion for many consumers.

Even the famous ANSI Checkboard Contrast Test (Read Below) is not used by all manufacturers as a standard despite it giving some great insight.

With that said, let us now look into the famous Contrast Ratio measuring techniques.

Types of Measuring Techniques

There are two famous contrast ratio measuring techniques

Nature of Contrast Ratio Test and Variables Affecting It

Before you learn about the testing methods, it is better to refresh some terms and a very simple mathematical representation of contrast ratio.

Rudimentary Mathematical Representation:

Contrast Ratio Equation 2

However, note that perfect dark is impossible in a normal situation. You can simulate total darkness in a laboratory and even then, there will be unwanted light that can compromise the black levels on the screen.

There are two common types of light sources that can affect the black levels as mentioned earlier.

  • Ambient Light: There is always ambient light such as light from your desk lamp, chandelier, sunlight entering through the window etc.
  • Stray Light: Stray light is emitted from the intended source, but does not travel on the intended path.


More On Stray Light:

Stray light is basically the light that is emitted from the intended source, but does not travel in the intended path.

We know that there are thousands of pixels in a screen. These pixels let the light pass when intended. However, in doing so, the lit pixels can also leak some of their light to the nearby dark (turned off) pixels.

Therefore, while the light did emit from the intended source (i.e the LED backlight), it strayed to the wrong path (i.e to the nearby pixels).

As a result, the Contrast Ratio of a device is compromised due to Stray Light, Ambient Light or both.

Therefore, even in a perfect laboratory setting if you were to completely remove the Ambient Light, you have Stray Light to worry about.

stray light v3

Effects of Stray Light

Better Mathematical Representation:

When taking all the variables into consideration, we can better represent the Contrast Ratio equation as follows:

Contrast Ratio Equation Expanded

With this mathematical representation in mind, let us now read up on the contrast ratio measuring tests.

1. Full On/ Full Off Test – Dark Room

The contrast ratio by the manufacturer is measured in a dark laboratory room. DARK ROOM means that we are in a perfect laboratory setting with no Ambient Light)

The first, and also the the most misleading test, is the Full On / Full Off Test.

This is what most manufacturers use to specify the famous Dynamic Contrast Ratio (DCR) of their display device. However, know that this test is meaningless to most extent.

You will see here why as we explain this mathematically using the equation we established above.

Method of This Test

On a Full On / Full Off test, as the name suggests, you either turn the screen to 100% white or 100% dark and then measure the contrast ratio.

full on full off

Misleading because no screen in normal situation is either 100% bright or 100% dark

Do you see the glaring error here? In a normal situation are all the pixels always on or always off? Consider a scene from a movie. Are there ONLY bright or ONLY dark spots? That is absurd to think off anyways.

As such, the Full On and Full Off Test is a misleading test and does not represent the actual performance of the display in a normal situation.

However, for argument sake, let us indulge ourselves with an example:

Lets recall the contrast ratio formula,

Contrast Ratio Equation Expanded

Lets use this to see how absurd the Contrast Ratio values are measured with the Full On/ Full Off Test.

The Absurd Infinite Contrast Ratio

Take 1000 nits as the max brightness (White Display Light) of your screen.

Why 1000 nits? While the average is 250-400 nits, some TVs and monitors CAN achieve 1000 nits especially those with HDR. Plus 1000 is an even number and good for easy explanation.

If you do a Full OFF Test in perfectly dark laboratory setting, the contrast ratio will be infinite.

How?

Well consider the following,

  • White Display Light: 1000 – because that is the max brightness of the screen.
  • Ambient Light: 0 – because we are in a perfect laboratory setting
  • Black Display Light: 0 – because we are doing a FULL OFF Test meaning all pixels are turned off – the screen is blank.
  • Stray Light: 0 – because since no pixel is turned on, there is no light leaking from one pixel to the other.

As such,

Full Off Test (infinity)

Do you see the issue here? How could you possible disregard the stray light. Of course, we all now that if a screen is literally turned off, it will have an infinite contrast ratio anyways. But it means nothing when an image or movie is displayed.

You may have come across some displays that actually make this claim.

However, infinity is a highly absurd claim.

The Absurd Millions:1 (1,000,000:1) Contrast Ratio

Infinity:1 is too absurd even for more established brands. Therefore, they resort to a more conservative number i.e billion:1, 10 million:1 or the most common 1,000,000:1.

While this is certainly way too conservative as compared to infinity, this still make no sense at all.

So how is an absurd number like 1,000,000:1 reached?

Well this is achieved, when the manufacturer takes a small hint of Stray Light into the equation (unlike the previous example when the Stray Light wasn’t considered at all).

In a Full Off Test, all pixels are turned dark. The Stray Light value is thus the “minimal detectable luminance” as measured by the sensitive testing instruments.

Even when all the pixels are turned dark, the sensitive instruments can still pick up some stray light in the range of about 0.001 nits

As such, if you now take this trace amount of Stray Light into the equation, you get a result similar to billions:1 or millions:1 contrast ratio.

Let us consider the following,

  • White Display Light: 1000 – because that is the max brightness of the screen
  • Ambient Light: 0 – because we are in a perfect laboratory setting
  • Black Display Light: 0 – because we are doing a FULL OFF Test meaning all pixels are turned off.
  • Stray Light: 0.001 – because our very sensitive measurement tools have detected some trace amount of Stray Light.

Therefore, when revisiting the equation,

Contrast Ratio (million)

Again, notice how absurd this claim is.

For starters, the manufactures are at full discretion to choose whatever the Stray Light value they want depending upon how sensitive their measuring tools are.

Secondly, again, the manufacturers haven’t considered the fact no screen is 100% black or 100% white in normal circumstance. When watching a movie, the pixels that turn on depend upon the image being displayed.

Therefore, unless you love looking at a blank dark screen that too in a perfectly dark room with ABSOLUTELY no ambient light, the contrast ratio of 1,000,000:1 is meaningless.

In normal situation the Stray Light would be much higher. On top of that, no pixel is a 100% black – even the darker pixels emit (leak) minute amount of light from the backlight source. Besides, you also have Ambient Light to consider in a normal situation.

2. ANSI Contrast Test (Checkboard) – Dark Room

The contrast ratio by the manufacturer is measured in a dark laboratory room. DARK ROOM means that we are in a perfect laboratory setting with no Ambient Light)

The Full ON Full OFF Test has glaring issues. It takes the most ideal scenarios where the screen is either 100% bright or 100% dark. Therefore, the resulting numbers are highly misleading.

The much better way to measure the contrast ratio is the ANSI Contrast Test. This is also called Checkboard Test since it uses several alternating boxes of white and black colors to make the test simulate normal situation.

In this test, the effect of Stray Light becomes much more clear.

Ansi Checkboard

Checkboard image is displayed on the screen for ANSI Contrast Test

For example consider the checkboard image above. If this image was shown on a display device, then the light from white boxes would also leak into the black areas thus affecting its contrast (Stray Light).

We saw this example earlier, but here is a review:

stray light v3

How well the screen handles the Stray Light here actually determines its quality.

Lets say that Stray Light on your display device is about 2 nits. Also lets take some realistic number for Black Display Light as 0.5 nits – since even in dark state, the pixels are emitting some trace amount of light due to the backlight leaking out.

Therefore considering our variables,

  • White Display Light: 1000 – because that is the max brightness of the screen
  • Ambient Light: 0 – because we are in a perfect laboratory setting
  • Black Display Light: 0.5 – because we have taken a more realistic values of dark pixels since no pixel is a 100% dark on conventional LCD TVs and monitors. (Read Backlight Bleeding)
  • Stray Light: 2 – because the lit pixels at white spots are leaking lights into the darker areas. This can vary depending upon the quality of the screen and its pixel control.

ansi checkboard equation

See how drastically the value of contrast ratio changes from millions:1 to a mere 400:1 with just some trace amount of Stray Light and a realistic number for Back Display Light?

This is actually a much more realistic value of a screen contrast ratio as compared to the absurd Infinity:1 or millions:1.

BUT, manufacturers would rather boast the gimmicky and flashy millions:1 contrast ratio that hold literally no meaning for the buyer.

Contrast Ratio in Normal Settings with Ambient Light

In normal settings, the actual contrast ratio perceived by you is something entirely different.

This has to do with the Ambient Light.

In the previous examples, the Contrast Ratio measurement were taken in a Dark Room Laboratory setting where no Ambient Light Exist.

In actuality, we all know that Ambient Light cannot be blocked out completely.

Depending on the setting, the ambient light can vary tremendously.

  • 50 nits – for a normal room
  • 100 nits – for an office
  • 1000 nits – for a screen in direct sunlight

Lets consider the FULL OFF Test with Ambient Light

Ambient light can have a huge impact on the contrast ratio of the monitor. It can significantly lower contrast ratio perceived on the display device.

For the purpose of an example here, lets take 50 nits of ambient light here (a normally-lit room).

Coming back to our equation above.

Ambient Light Contrast Ratio

You may be surprised by this number i.e 21:1 because it way too low than you would expect.

However, don’t worry too much about this since this particular example is just to highlight the effects of the Ambient Light and does not reflect the actual quality of the display.

The Contrast Ratio value in various ambient light condition is not specified by the manufacturers because, to be fair, the manufacturers have no idea about where and in what conditions you will be using your device in.

However, they do specify the Surface Coating used on the device. The two most common are Matte and Glossy.

  • Matte Surface – Great at blocking out Ambient Light from affecting the Contrast Ratio. Unfortunately, it also blocks some of the backlight of the device does affecting the vibrancy of the colors.
  • Glossy Surface – Does not block out the Ambient Light. However, it is preferred in dimly lit environment since it lets all of the backlight pass through.

Static (Native) Contrast Ratio vs Dynamic Contrast Ratio

We will review Static and Dynamic Contrast Ratio from a consumer’s point of view later in the article (Read Below) since these terms are quite popular on display devices.

However, for now let us see how they are tested and defined.

Static Contrast Ratio

Static (Native) Contrast Ratio is deemed as one the most important measurement of the quality of the screen.

The Static Contrast Ratio is the true value of the contrast ratio since it is measured when the panel is manufactured.

While the testing is still performed in a Dark Laboratory Room without any Ambient Light interference, it is the one number that all buyers should look for.

Static Contrast Ratio is the ratio of the difference in luminosity between the brightest and the darkest color produced on a STATIC Frame i.e on a single frame like picture, photo or a single frame of a movie.

The value of the static contrast ratio is generally as follows:

  • IPS Panel: 1000:1
  • TN Panel: 1000:1
  • VA Panel: 3000:1

Static Contrast Ratio is the least misleading number.

static contrast ratio

You want go for the highest Static Contrast Ratio as possible

How is it Tested?

Static Contrast Ratio of a panel is measured before any image processing technologies or backlighting features like Local Dimming are added to the display.

Basically, it is the most RAW and the truest measurement of the Contrast Ratio. The testing is mostly standard across the manufacturers since all it requires is a dark laboratory without any ambient light interference. Therefore, this adds more trust to this particular number.

Since it relates to a typical STATIC situation like looking at a photo or a single frame of a movie, it is NOT based on the misleading FULL ON or FULL OFF test we read about earlier.

Dynamic Contrast Ratio

Dynamic Contrast Ratio is the ratio of the difference in luminosity between the brightest and the darkest color produced OVER A SPAN OF TIME.

Note the key difference, Static Contrast Ratio refers to a still image or a single frame. On the other hand, Dynamic Contrast Ratio refers to Contrast Ratio recorded over time.

Here is how,

The backlight on the TVs or monitors does not stay steady. Meaning, TVs and monitors have technologies that automatically adjust the brightness of the screen depending on the scene shown.

These are called Dimming Technologies and we discuss them below.

Therefore, when a bright image is displayed, the screen automatically brightens up the backlight and vice versa if a dark image is displayed.

Therefore, if you take the DCR values at different times, the value will be entirely different. The darker the scene, the higher the DCR will record its value.

Unfortunately, this number can be quite misleading though. Since it takes into consideration the Full ON and Full OFF scenarios as discussed earlier.

For example, if a scene on a movie shows a completely black screen, the contrast ratio will naturally go all the way to about million:1 (read Full OFF Test above).

Yet, on a normal static, or a still, frame like a photo, the best contrast the display would produce would still be limited to the Static Contrast.

For example, even if the Contrast Ratio went all the way to million:1 in a completely Dark Scene (thanks to DCR), when looking at a meaningful frame like a selfie photo you took the other other day, the Contrast Ratio will be limited to the Static Contrast Ratio of the screen.

While a full black screen that appears on a movie means nothing to the viewer and contains no details, the Dynamic Contrast Ratio will still be recorded for that particular scene as million:1. This is what makes DCR mostly a useless spec.

DCR v5

On top of that, a display with a high Dynamic Contrast Ratio and a bad Static Contrast Ratio would also perform badly in darker scenes as the leaking backlight will make it hard to discern small details in darker scenes.

Bottom line, pay attention to the Static Contrast Ratio specifiction!

How is it Tested?

There is absolutely no standard for testing this. However, usually, it is tested on the basis of the flawed FULL ON / FULL OFF Test we talked about earlier above.

The manufacturers only specify the maximum DCR recorded when the screen had gone blank.

On top of that, DCR is tested after technologies and features such as image processing chips and Local Dimming (Read Below) features have been added.

Since technology differs from manufacturer to manufacturer, there is not one standard and as such:

YOU CANNOT JUDGE A DISPLAY DEVICE BY ITS “DYNAMIC CONTRAST RATIO”

Note on Panel Types

Brief Note on Panel Types

Here it is worth mentioning that there are various panel types available for TV and monitors.

We go over the inner workings of a display and pixel control in the section below.

A monitor panel is basically where all the circuitry of the pixel goes in. The panel determines how good the pixel control of a display device is.

A bad panel would allow Stray Light and Backlight Bleeding to affect the Contrast Ratio of the display. A good panel would reduce as much of the Stray Light and Backlight Bleeding as possible.

There are basically three types of panels available in the market: TN, IPS and VA. They have the following Static Contrast Ratio values.

  • TN: 1000:1
  • IPS: 1000:1
  • VA: 3000:1

While the DCR can be in millions depending upon the product, the Static Contrast Ratio is mostly standard across brands.

Dimming Techniques – Local Dimming and Improved Contrast Ratio

One way to improve the contrast ratio of the screen drastically is to introduce Backlight Dimming Features.

What Does that Mean?

Dimming technology pertains to the various technologies TVs and monitors use to improve the Contrast Ratio by automatically controlling brightness of the backlight.

We learned from earlier that it is not possible to achieve a 100% Dark state on an average LCD. Issues such as Backlight Bleeding and Stray Light, among others, can affect how deep the blacks can be shown.

Since the backlight on a conventional TV or a monitor stays uniform, it cannot do anything to control the brightness of various sections of the image.

For example, on a conventional TV or a monitor if you have one half of the screen brightly lit for a bright image and the other half of the screen dimly lit for a dark image, the darker half will not be perfectly black.

However, dividing and controlling the zones of the backlight for darker and brighter zones individually can improve the overall contrast ratio.

Direct-Lit (Global Dimming) and Its Issues

Conventional and low budget monitors and TVs use the Direct-Lit technique which goes by many names i.e global dimming or uniform backlight.

With this technique, the TV has no control over controlling the individual zones of the backlight separately. Hence the brightness is uniform across the screen.

In other words, as the brightness is dialed up or down, the entire scene gets brighter or darker.

global dimming v2

Direct-Lit is an automatic technique and the TV controls whether to ramp up the brightness or dial it down depending on the scene shown.

The issue here is that since the dimming and brightening is uniform, when a predominantly bright scene comes up, even the darker few patches in the image will look brighter.

This is because the TV has automatically made judgement to brighten up the screen for the current image. This judgement would also affect the darker patches. Vice Versa when a dark scene comes up.

Local Dimming to the Rescue

Local Dimming is found on more expensive TVs and monitors. However, it can help with Contrast Ratio tremendously.

As mentioned earlier, with Local Dimming, the backlight gets divided into zones as supposed to Global Dimming. Each zone can then be controlled individually by TV / Monitor depending on the picture or the frame being shown.

There are two types of local dimming techniques as mentioned below.

1. Full Array Dimming

full array dimming

This is the more expensive of the two techniques.

As the name suggests, in this technique the backlight consists of an array of hundred of LED lights which are then divided into zones.

While the most ideal case would be to control each and every LED light (Read OLED), due to the technology restrictions on conventional LCDs, zones are setup which are then controlled individually by the TV.

Therefore, with each zone controlled individually the effects of Stray Light and Backlit Bleeding are decreased immensely.

Again, since this is one of the most expensive backlight control techniques on TV and monitors, it is generally found on products that are cream of the brand.

2. Edge-Lit Dimming

edge lit v2

Edge-lit technique is somewhere in between Direct-Lit and Full Array Dimming techniques.

In this technique, as the name suggests, the LED lights are arranged on the edges, or the perimeter, of the screen.

While this technique does not provide as much control as the zonal control in Full Array dimming, it still helps in improving the contrast ratio by a good factor.

The Edge-lit dimming still grants some brightness control over how different parts of the screen are shown.

Most mainstream TVs these days have edge-lit dimming instead of a Direct-Lit technology.

Edge Lit TVs and Monitors can be differentiated by their very thin form factor. Not only are they thin from the side, they are also have very thin bezels.

OLED – Infinite Contrast Ratio?

OLED is such an important technology that it deserves a section of its own here.

Recall from earlier that LCD TVs and Monitors utilize a Backlight that shines across the pixels to create an image.

As such, the backlight is a crucial element as without it, you will basically have a plain dark screen even if you have videos playing on it.

What OLED does is removes this backlight altogether. As such OLED have NO BACKLIGHT at all.

How is that Possible?

If there is no backlight, how is the light generated?

Basically OLED uses an organic compound that individually glows when a voltage is applied across them.

In fact the name OLED is short for Organic LED.

How Does This Improve the Contrast Ratio?

OLED gives the ability to control the backlight of each and every pixel individually.

Recall from earlier that

  • Direct Lit techniques dims and brightener the entire screen uniformly
  • Edge Lit technique gives some control by controlling the brightness on the perimeter of the screen
  • Full Array technique gives plenty of control as it divides pixels in to zones.

Organic LED, on the other hand, trumps this all by giving each and every pixel a separate light of its own.

Instead of the entire TV having a backlight, here you have each pixel with a backlight of its own. There are millions of pixels on a TV so you can imagine the control on the quality of picture with an OLED TV.

What is the Contrast Ratio of an OLED?

As you may have guessed, the contrast ratio of an OLED is inifite:1.

It makes sense because when an OLED goes dark, the pixel literally just goes OFF – it literally produces no light at all.

There is no Stray Light or Backlight Bleeding diffusing through the dark pixels unlike conventional LCDs since there is no LED backlight array at the back at all.

Of course it is infinite:1 only in dark laboratory settings, in a normal situation, like in a room, you have Ambient Light affecting the perceived contrast ratio.

Nevertheless, OLEDs have the ultimate Contrast Ratio and if you seek perfection, then you know this is the display to go for.

How is the Image on the Monitor/TV Produced?

To solidify your understanding of Contrast Ratio, you may need to have some brief knowledge about how an LCD device works. ESPECIALLY, how a pixel works.

In short a typical LCD is made up of three components:

  1. Backlight
  2. Pixel
  3. Front Panel

1. Backlight

Also known as the source light. This is the primary source of light that is measured in nits or candela/square meter (cd/m2). It is the main source of how intensely the light is emitted from the display device.

Most monitors have a backlight intensity between 250-350 nits.

In most cases, the backlight source stays uniform across the screen – [unless if the device has Local Dimming features (Read Above)].

Therefore, whether you choose to dim or brighten the light intensity of your monitor or TV, the effect would take place across the entirety of the screen.

The uniform backlight is also called Global Dimming and is the opposite of the Local Dimming. It is the standard backlighting technique on budget monitors and TVs.

2. Pixels – Very Important for Contrast Ratio

Pixel v2

Read below to better understand this image. I believe this image is by far the most simple and best representation of how a pixel works. Source: Researchgate.net

This is where the magic happens. A pixel transforms a simple wave of backlight into a noticeable color.

A pixel is made up of several sub components as we will read below:

The following is a simplified representation

a. Vertical Polarizing Filter

Light is naturally “unpolarized” meaning it is moving in all directions. However, if we want to extract only the light moving in a certain direction, we can make it do so by polarizing it.

This can be done via Polarizing Filters. These filters have small slits across them that only allow light waves moving in a given direction to pass through.

Sunglasses work this way since sunglasses are made of polarizing filters that only allow light traveling in a certain direction to pass through.

Therefore, the first polarizing filter in an LCD is a vertical polarizing filter. This only allows vertical light to pass through.

Think of polarizing filters as “gates”. Therefore, a vertical gate will only allow vertical light to pass through

b. Horizontal Polarizing Filter

A horizontal polarizing filter allows only the horizontal moving waves to pass through it.

Note that when you stack a vertical polarizing filter over the horizontal polarizing filter, no light will pass through. In essence all light will be blocked.

But, this raises the obvious question: if all light would be blocked by the two opposing polarizing filters, why then do we see the light emitted from the LCD in the first place?

This is where Liquid Crystal comes into play.

c. Liquid Crystal

A liquid crystal has an amazing property of twisting the light. 

In its natural state, a liquid crystal can twist the light thus essentially turning a vertical light into a horizontally oriented light. This is where the term Twisted Nematic comes from – in case you are wondering.

This is the reason why we see the light on the display despite having two opposing polarizing filters on top of each other.

This in turn raises the question: Well if the light is all passed, thanks to the liquid crystals twisting the orientation of the light, how would we see dark images? After all, the light has to be blocked in order to see dark or black colors right?

This is where things become very interesting.

Basically, when a voltage is applied to the liquid crystal, its structure breaks down. As a result, the liquid crystal looses its ability to twist the light.

Thus, the pixel becomes dark and does not let the light pass through.

Therefore in a typical LCD you will have thousands of pixels letting the light pass through and at the same time thousands of pixels that are blocking the light since they have a voltage applied across them. All in the effort of displaying the intended image.

The Pixel Never Goes 100% OPAQUE/OFF – Important

The pixel simply becomes DIM.

It is not possible for the horizontal polarizing filter to completely block out the light in normal situations.

If pixels next to darker pixels are lit up, they can scatter or creep some of their light into the nearby pixels that are supposed to be OFF.

This is called Stray Light and we have discussed this extensively above.

Some displays are better at blocking the creeping light from the nearby pixels and others are not.

Those displays that are exceptional at blocking the Stray Light, have a higher contrast ratio. Hence, they show deeper blacks and brighter whites.

Now the number 1000:1, 2000:1 and 3:000:1 etc should start to make sense.

To reiterate the definition, 1000:1 contrast ratio means that the pixel can be a 1000 times brighter than its darker state.

This also entails the fact that the pixel isn’t really 100% OFF in its darkest state, otherwise the contrast ratio would have been infinite.

Type and quality of liquid crystal affect the contrast ratio. Different panel types uses different types of pixels.

If all LCDs were created equally, we wouldn’t be having this discussion at all.

However, the type of Pixel Panel as well as their quality matters.

d. Electrode Plates

This is basically the circuitry found on the liquid crystal that allows current to pass through to turn the Pixel OFF.

When a voltage is applied on the electrodes, the Nematic Molecules of the Liquid Crystal orient themselves to the Vertical Orientation of the Vertical Polarizing Filter (vertical gate).

Thus, the light now in vertical position would not pass through the Horizontal Polarizing Filter (horizontal gate). The pixel is then said to be OFF.

If this all seems to confusing, it would be worth it to review the pixel image above.

Light and Pixel

Wrapping up the Passage of Light in a Pixel:

This is how the passage of light works when the Pixel is ON (Light Passes Through)

  1. Light enters via the vertical polarizing filter on the back.
  2. It then passes through liquid crystal which twists it to horizontal orientation.
  3. Thanks to this twisting, the light is then capable of passing through the horizontal polarizing filter.
  4. Behold, you see the light.

This is how the passage of light works when the Pixel is OFF (Light is Blocked)

  1. Light enters via the vertical polarizing filter on the back
  2. A voltage is passed through the liquid crystal
  3. The structure of the liquid crystal breaks down and thus it not capable of twisting the light to horizontal orientation.
  4. The light is thus incapable of passing out from the horizontal polarizing filter.
  5. The pixel is considered off.

e. Color Filter

pixel array color

Each pixel also has Red, Green and Red color filter on top of the liquid crystal.

Each color is called a Subpixel and it is controlled indivudually.

The order of the components within a pixel is thus as follows

  1. Vertical Polarizing Filter
  2. Electrode Plate
  3. Liquid Crystal
  4. Electrode Plate
  5. Horizontal Polarizing Filter
  6. Color Filter

Again, this is a simplified representation.

3. Front Panel

This is the final component of the LCD screen.

The front panel can have glossy or matte finishing as protective covers.

Glossy vs Matte

A matte finishing blocks the Ambient Light and does not suffer from light glare from brightly lit environment. However, they have reduced Contrast Ratio as they also block the intensity of the backlight.

A glossy surface is bright, and has a better contrast in ideal situations however, it is affected by the Ambient Light glare. This can essentially harm the perceived contrast when in brightly lit rooms.

Most monitors have a matte finish. While monitors with touchscreens have a glossy panel.

Buyer’s Guide

Most of you probably do not care much about the intricacies and the details of Contrast Ratio as we shared above.

If you are a consumer and want to make a beeline for what Contrast Ratio means for you, read below.

What is the Importance of Contrast Ratio?

Simply put, Contrast Ratio determines how deep the dark and how bright the colorful areas of the image will be produced.

You must always strive to go for a higher Contrast Ratio.

A high Contrast Ratio is a direct reflection of the overall quality of the monitor or the TV.

Static Contrast Ratio (Native)

One of the most important number to take into account when looking at a TV or a monitor is its Static Contrast Ratio. This value is always mentioned in the spec sheets.

Static Contrast Ratio is the truest representation of how deep the dark areas of the picture will be.

The usual numbers are as follows for different panels.

  • For TN Panel: 1,000:1
  • For IPS Panel: 3,000:1
  • For VA Panel: 5,000:1

Dynamic Contrast Ratio – Why This Can be Misleading

Dynamic Contrast Ratio (DCR) is the Contrast Ratio that the screen measures at over a span of time.

For example, when watching a movie, some times the screen may become too dark and some times it may become too bright depending on the scene.

The Dynamic Contrast Ratio will thus change over time.

While Dynamic Contrast Ratio in itself is quite valuable, unfortunately, the numbers specified on the specsheet for DCR are highly misleading.

Pros of DCR

DCR basically entails the backlight technology being utilized.

It tells you that the TV or the monitor employs the technology to automatically dim or brighten the picture depending upon the colors of the image shown.

Imagine if you have to manually control the brightness for each and every scene of the movie.

DCR saves you from this hassle and depending upon the Backlight Dimming technique used, the overall Contrast Ratio can significantly be improved:

  • Direct-Lit – Uniform Backlight – Limited DCR Control
  • Edge-Lit – Brightness control on the perimeter of the screen – Better DCR Control
  • Full Array – Backlight divided into zones – Excellent DCR Control

Compilation v2

Cons of DCR

The issue with DCR is that its specified value on the specsheet can be VERY misleading.

You may have come across numbers like 50,000,000:1 or the more conservative 1,000,000:1 DCR values.

These absurd values mean absolutely nothing to you as a consumer.

These absurd numbers are basically achieved when a full dark scene occurs. In that instance, the contrast ratio will naturally go high since the entire screen is black.

However, as soon as a meaningful image is shown, the DCR value goes back to a moderate number.

The reason why this number is so misleading is because the brands use the dark scene or the full blank screen as the standard of measurement instead of a normal meaningful scene to exaggerate and show off their DCR numbers.

So unless you love staring at a blank screen, DCR numbers like gazillion:1 would mean nothing to you.

Read Full On Full Off Test above to better understand this.

OLED Displays

OLEDs are probably the best thing that has happened for the Contrast Ratio. These TV and monitors have the highest contrast ratio achievable.

The Contrast Ratio is literally infinity:1.

How?

Recall, that all LCDs have a backlight for illuminating the pixels. Without the backlight, you would see nothing.

You have the Direct-Lit backlight, Edge-Lit backlight or the Full Array backlight.

As such on a conventional LCD, backlight is indispensable.

OLED or Organic LED completely overturns this notion.

Here, instead of having a backlight at the back, each and every pixel has it own light generating organic compound.

As such, you get unlimited control over each and every pixel.

In short, if you want the best Contrast Ratio possible, go for OLED TVs.

Backlight Bleeding

Backlight Bleeding is the ugly issue that occurs on substandard TVs and monitors in which you can visibly see backlight creeping out from the back into the darker regions of the picture.

backlight bleeding

Example of Backlight Bleeding. Source: Shephard4711 @ Flickr

This can have a huge effect on the Contrast Ratio of the screen.

Ideally when in blank state, the screen should be 100% black. It should be PITCH BLACK NOT GRAYISH BLACK.

However, on any LCD some light can creep out. This occurs even in fairly expensive products. Therefore, some Backlight Bleeding is quite normal.

However, Backlight Bleeding to the extent as shown above is horrible and can significantly hamper your viewing experience.

What We Recommend

Testing a product for Backlight Bleeding is quite simple, just ramp up the brightness of the screen. Make sure it is not connected to any source like a PC.

It is also highly preferable that you turn off the room lights. However, since this is mostly not possible in a shop, we recommend that you also test it out at your home with room lights completely turned off.

Return or ask for a replacement for the product if you observe a significant amount of Backlight Bleeding.

Online reviews can also help pre-purchase.

Glossy Vs Matte Surface Panel

The surface panel used on the screen significantly affects the perceived Contrast Ratio.

There are two types of Surface Panels

  • Matte
  • Glossy

Glossy vs Matte

Matte Surface

A matte finishing blocks the Ambient Light and does not suffer from light glare from brightly lit environment. As such, for offices or a brightly lit room, matte surface is the way to go.

Unfortunately, in an effort to block the Ambient Light and Light Glare, it also reduces the intrinsic Contrast Ratio of the screen itself. As such, the colors shown are less bright and vibrant.

Glossy Surface

A glossy surface (glass) is usually found on touch devices as well as on many TVs.

Glossy surfaces do not protect against light glare. Therefore, if you were to take glossy devices in a brightly lit room, you may get a hard time distinguishing the darker regions of the image.

However, at the same time, they deliver the truest contrast that the screen can deliver. It does not block the colors or light coming from the back.

Therefore, designers and photographers may prefer glossy surfaces over matte surfaces. Just make sure you place the device in a moderately lit room.

Panel Technologies

We have covered earlier that there are three main types of panels used in TVs and LCDs. They are as follows with their corresponding Static Contrast Ratio Numbers.

  • IPS Panel: 1000:1
  • TN Panel: 1000:1
  • VA Panel: 3000:1

Lets go over them one by one.

TN Panels

  • The oldest of them all.
  • They have the fastest Response Timetherefore are preferred by gamers.
  • Due to the way the pixel circuitry is designed, TN suffers from narrow Viewing Angles. This results in uneven colors when viewing from an angle.
  • Monitors featuring TN panels are generally the cheapest.
  • They are not preferred by designers, photographers or anyone who wants color perfection.
  • They usually feature the highest refresh for the price

IPS Panel

  • They are the most sought after panels by designers and photographers.
  • Even though they have the same Static Contrast Ratio as the TN panels, they produce much more vibrant colors due to the way their pixels are arranged.
  • They usually have a higher Color Bit Depth and can reach 10 and even 14 bit depth with 3D LUT.
  • Their colors are precise and thus IPS monitors can create better tonal variations.
  • They are more expensive – especially the premium panels found on professional grade monitors.
  • They suffer from the slowest Response Time – therefore not sought after by professional gamers.
  • Widest Viewing Angles which promotes color uniformity across the screen.

VA Panel

  • They have the highest Static Contrast Ratio – they hold the crown on LCDs display for best Static Contrast Ratio.
  • Also preferred by designers and photographers like IPS panel.
  • Generally found on curved displays.
  • Picture quality is in between TN and IPS panels – more leaning towards IPS panel.
  • Response time is in between TN and IPS panels – therefore can be preferred by gamers.
  • Viewing Angles are as great as IPS panels

Final Words

This concludes our guide on what is Contrast Ratio.

If you feel we have missed something here, or if you feel we have misrepresented something here, please feel free to write to us.

While we understand that most of the information here would not relate to average consumer, we have, nevertheless, striven to provide an insightful look into Contrast Ratio in a simple way for all.

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