How To Check Smartphone Display’s Quality

How To Check Smartphone Display’s Quality

Youtube Reviewers and Tech Bloggers often say that the display of a smartphone is great, good or bad. That’s one way to know about the quality of a smartphone. But it does not tell you anything about how much a display is better or worse than the other smartphone displays on the market.

This is a problem that I have faced too and I am at a point where If anyone says that the display is pretty good for its price, I get irritated. Like what are you talking about?

Is it good just for you or for everyone else?

Is it better or worse than the competitors?

Are we just supposed to take your word for it?

It is not an OLED, so it must be bad? (Yes, IPS LCD’s could be better than an OLED)

Is the display good for average consumers or gamers?

These are all the questions I had a couple of years ago. All I could find on websites and Youtube is that the display of a certain smartphone is good, average or bad. Even the most renowned Youtubers would just say Samsung has the best display (bright, vibrant, good viewing colors and excellent) without providing any proof to back up their claims.

Although I am not implying that they don’t know what they are talking about. But I would say that they are not providing enough details for consumers to convince them.

Well, I would try to explain everything you need to know about display quality to the best of my knowledge.

This article will cover:

  • Factors affecting smartphone display performance.
  • How to check the smartphone display quality from different sources on the internet.
  • Different display terminologies like Response Time, Color Gamut, etc.
  • Display Brightness and APL (Average Picture Level)
  • Display Brightness Control and Flickering (PWM)

This article will not cover:

Factors Affecting Display Quality:

There are probably more than twenty (20) factors that could affect smartphone display performance. But to keep this article easy for most people, I would only enlist and explain the factors that are most crucial in determining a smartphone display quality.

Let’s Start.

Color Gamut:

Color Gamut represents the range of colors that a display is able to produce. The wider the range of colors a display can produce, the better. The higher color gamut is required for HDR (High Dynamic Range) which enables your smartphone to play high-quality Netflix and YouTube content.

It is represented in the percentage of different color spaces which are sRGB and DCI P3. I will only talk about sRGB and DCI P3 color spaces because you will only encounter these two in smartphones.

In simple terms, A Color Space is an abstract mathematical model that explains defined ranges of colors and tones that a digital file can handle. The CIE 1931 color system represents all the range of colors that our human eye can perceive.

They are of various types of Color Spaces but the popular ones being:

  1. NTSC
  2. Adobe RGB
  3. DCI-P3
  4. sRGB

Starting with the smallest one in range, sRGB is the most popular color gamut used for most applications including web, photos, and even graphics. In recent days, most displays cover complete sRGB gamut. Moving on, Adobe RGB covers the entire spectrum of sRGB and it is a much wider color gamut. It is mostly used for professional applications like DSLR images and printer.

If this confusing to you. Let me make it easy by giving you the numbers. If a display has 100% coverage of the sRGB triangle in the CIE 1931 color system, then the percentages for the other three color spaces in the CIE 1931 with respect to the sRGB triangle are given in the table below.

Color SpaceCoverage
sRGB100%
Adobe RGB 116.7%
DCI P3125.6%
NTSC127.5%

So, if a smartphone supports DCI P3 100%, it means it covers 25.6% more area than the standard sRGB colors area. Most of the specifications of the smartphone would not indicate whether they are sRGB 100%, above or below. This is why you need to look at the reviews from websites that do provide this information.

I rely on NotebookCheck for this information. Just to give you an idea of the coverage of colors of different smartphones from 2019. Look at the table below.

SmartphoneColor Gamut
(sRGB
)
(Higher is Better)
Xiaomi Mi Note 10 138%
Huawei Honor 20 98.6%
Samsung Galaxy A70 98%
Asus Zenfone 6 98.7%
Huawei Nova 5T 99.9%
Google Pixel 3A XL 100%
Realme X2 Pro 125%
OnePlus 7 99.7%
Xiaomi Mi 9T Pro 142.2%
Apple iPhone XR 100%

This is one of reasons that just looking at whether the display is an OLED or LCD is not enough. An LCD could have much higher color Gamut than an OLED in similarly priced smartphones. Most of the Budget or even Mid-Range smartphones do not even have 100% sRGB coverage which is a shame.

If you need to find out Color Gamut of any smartphone, you can find it by looking at the NotebookCheck review of that smartphone. In the review, Go to the display section and look at a table in that area.

notebookcheck
Source: S10 Review Notebookcheck

Keep in mind, the Color Gamut represents a range of colors that a display can produce, the wider the range of colors a display can produce, the better the dynamic range and Image Quality. Color Accuracy is not the same as Color Gamut.

However, I have to clear one important point here. Most of the Smartphones Color Gamut for sRGB and DCI-P3 are written separately, so make sure to check coverage for both. For example, The Color Gamut for sRGB and DCI-P3 of Xiaomi Mi Note 10 is given below.

It is common to write the percentage of sRGB more than 100% for some smartphones, but it is not the only way. Look at the results for the OnePlus 7T Pro.

This is why do not get confused by these two different ways to write Color Gamut. Just look separately at the Color Gamuts of sRGB and DCI-P3.

Color Accuracy

The Color Accuracy refers to a display’s ability to produce the exact color tones or shades of grey as requested by the source signal or application. No display is 100% color accurate. This is why we have to measure how much the colors of a display deviate from the original colors. This deviation or difference of colors from what the display is supposed to produce is represented as ΔE for color and grayscale separately.

Smartphone: Mi Note 10, Source: PhoneArena

As you can see from the above picture, the colors produced by the Mi Note 10 are slightly different from the actual colors. If there is a difference between the actual colors and the colors produced by the display of Mi Note 10 even when we are comparing them using only one shade of color. This difference in color would be huge if we compare a large number of colors.

The grayscale (Black and White) is also compared.

Smartphone: Mi Note 10, Source: PhoneArena

The above figures are just to show the difference in colors from a visual standpoint. But we can’t really compare smartphones’ color accuracy by looking at each of them visually. This is why we use ΔE for color and grayscale to measure the color accuracy in numbers. The numbers can then easily be used to compare the color accuracy of different smartphones.

The higher the delta value, the more the difference in colors and the lower the delta value, the better the color accuracy. I would suggest you read this great article from nixsensor website to understand the color accuracy. Let’s look at the triangle which is used to determine the color accuracy delta.

There are some squares and some circles inside the triangle. Ideally, the circles should be inside and at the center of the squares for perfect color accuracy. Also, the closer the circles are to the squares, the lower the delta E (ΔE) number and the better the color accuracy.

Let’s look at the delta E (ΔE) values for Xiaomi Mi Note 10 and Apple iPhone 11 Pro Max to understand the difference. The Mi Note 10 display is really good but Apple iPhone 11 Pro is one of the best if not the best display on the market.

If you ask me, Apple 11 Pro Max display is better than Samsung Note 10 display which no one ever says or even considers. Well, don’t take my word and look at the values yourself.

So, the lower the Delta E (ΔE) number, the better the color accuracy. You can check all of these results at Notebookcheck.net.

Let’s look at the Delta E (ΔE) of the color of some of the Mid-Range Smartphones of 2019.

SmartphonesColor Accuracy (ΔE)
(Lower is Better)
Xiaomi Mi Note 10 4.38
Huawei Honor 20 1.1
Samsung Galaxy A70 3.3
Asus Zenfone 6 3.5
Huawei Nova 5T 6.6
Google Pixel 3A XL 1.3
Realme X2 Pro 5.2
OnePlus 73.5
Xiaomi Mi 9T Pro1.51
Apple iPhone XR1.3

IPS LCD panels of iPhone XR and Huawei Honor 20 color accuracy are way better than most of the O-LED panels here. Another reason why O-LED is not superior to LCD in every aspect.

Display Brightness

A Display Brightness is measured in nits or cd/m². Candela per square meter is the SI unit for luminance whereas nit is a non-SI unit. But both are same quantitatively i.e. 1 cd/m² = 1 nit. Another unit of light intensity is Lux. The relation between Lux and Nit is 1 Lux= π x Nit. So if we multiply pie (π) with nits, we get lux. In Simple words, 100 nits are equal to 314 lux.

According to Sciencing.com,

Lux and nits are both measurements of illuminance or illumination. In other words, they are measures of the intensity of light. Analogous to force, the unit “lumens” measures how hard light is pushing off of a light source. When it’s spread out over a specified flat surface, you get lumens per square centimeter, analogous to pressure. One lumen per one square centimeter is exactly 1 lux. Similarly, a nit measures light “force” per steradian – essentially, per a curved surface.

Normally, the higher the brightness of a smartphone, the better. It is really easy to find the brightness of any smartphone screen as most reviews would cover the max brightness of the display. But you guys know by now, that I use Notebookcheck for most purposes.

Unlike our computer screen or TV, we have to use our smartphone in outdoor lightings. The higher brightness is a must if you are continuously using your smartphone in an environment of 1500 lux or above. Look at the pictures below to see what happens to a smartphone display once the ambient light increases.

Source: Display Mate

Peak Brightness: The higher the peak brightness, the better. For reference, iPhone 11 Pro Max has 790 nits brightness.
Screen Reflectance: The lower the screen reflectance, the better. For reference, iPhone 11 Pro Max has 4.5% screen reflectance.
Ambient Light Contrast Rating: Higher the contrast rating, the better. For reference, iPhone 11 Pro Max has a 171-201 contrast rating for ambient light.

To understand brightness in different external lighting conditions, look at the table below:

External Light Condition or Activityilluminance or Brightness
(Lux)
Room with no light0-10
Public Area with dark surroundings20-50
Building Hallway lighting, Stairways, Escalators50-100
Residential Indoor Lighting, Light Offices, Class Rooms100-300
Kitchens, Laboratories, Library, Auditoriums, Normal Offices300-500
Mechanical Workshops, SuperMarkets, Operation Theaters, Max Indoor Lightings500-1000
Studio Lighting, outdoor lighting in shade, overcast sky, Drawing Work1000-5000
Shadow in direct sunlight, Dim outdoors5000-10000
Full Daylight but not direct sunlight, Cloudy Outdoors10000-25000
Direct Sunlight32000-100000

Most of the smartphones these days have at least 400 nits brightness. So you can expect these smartphones to perform well for the outdoor light intensity of around 15000 lux. At 2000 lux, we can easily see what the external light is doing to the smartphone displays. At around 2000 lux or more, the display color accuracy, color gamut, contrast ratio, and viewing angles change significantly. Therefore, The higher the external or ambient light, the lower the picture quality of your display.

Even if you don’t use your smartphone in extreme outdoor lights, it is always nice to have the option of a more bright display. So my suggestion is to buy a smartphone with at least 400 nits display brightness at 100% Average Picture Level (APL) for an OLED or 500+ nits for an LCD. But what is the Average Picture Level (APL)?

Average Picture Level (APL):

The brightness of an OLED display is variable, unlike LCD. The brightness increases with low APL and decreases with high APL.

In easy words, APL is the percentage of the pixels that are lit up compared to a full white display. For example, if all the pixels of a screen are fully white, APL would be 100%. If all the pixels of a screen are fully blue, APL is 33%. Similarly, if all the pixels of a screen have only one color (could be any color except white and black), APL is still 33%. Similarly, if 33% of the pixels on a screen are white and 67% are black, the APL is still 33%.

Average Picture Level or APL depends on the number of pixels that are active. The higher the active number of pixels (no blacks), the higher the APL.

Note: APL is only for OLED’s. The maximum brightness of LCDs is relatively fixed.

APL basically tells us how many pixels are active for a certain picture. APL changes the brightness of an OLED screen significantly. Look at how the brightness of Samsung Galaxy S20 changes with APL. I chose Samsung for example because Samsung Displays brightness varies very slightly on changing the APL.

In an OLED display, each pixel is on for a full white picture and off for a black picture. But the content we watch uses different colors. Some pixels produce red, some blue and some green. some pixels are off for black color, some are mixing RGB for full white color. Some pixels that are off, so they do not consume any power at all, this power is allocated to other pixels that are on. This is how extra power is allocated to pixels which helps these pixels to produce more brightness.

Let’s assume only 50% of the pixels on a screen are displaying content and the other 50% are off ( black color). All of the power would be allocated to the 50% pixels that are displaying content, which means these pixels can produce more brightness because of extra power from the off pixels. This is what 50% Average Picture Level is.

In a case where only 1% of the pixels are display content and 99% of the pixels are black which means off. All of the power would be allocated to 1% pixels. Therefore, these 1% displays would so much brighter than 50% APL. This is called 1% APL. You can look at the picture to see how much brighter the display is at 1% APL. But we rarely watch content which only lights up 1% of the pixels.

You should at least look at the 50% APL if you want to get an idea of what the display brightness is. With dark modes in each application, most of the time, the APL is around 40%.

Have a look at the brightness of famous smartphones with 50% as well as 100% APL.

Source: XDA Developers Pixel 4 display review

Read this article from Anandtech if you want to learn more about APL.

Looking at a display brightness without any idea of what the APL is, is not a correct way to measure the brightness of an OLED.

Brightness Control:

There are two ways to control (increase or decrease) the brightness of a smartphone display.

  • DC Dimming
  • PWM (Pulse Width Modulation)
Left: PWM Right: DC Dimming
Source: SmartPrix

You can do this yourself. Just look at your smartphone screen from another smartphone camera. If there is a flicker like in the left image, the smartphone is using PWM at that brightness. If there is no flickering like on the right image, the smartphone is using DC Dimming at that brightness.

Some smartphones use DC Dimming for high brightness above 50% and PWM for lower brightness levels. This is what Apple does in iPhone XS to give us the best experience.

PWM:

The brightness of the smartphone display is controlled by turning off and on the LEDs in pulses. If the required brightness is 80%, the LEDs will be on for 80% of the time of a full digital signal. If the required brightness is 20%, the LEDs will be on only 20% of the time of a full signal. This is done rapidly like more than 200 times a second to be unnoticeable by the naked eye. This is also the frequency of the PWM normally more than 200 Hz or Hertz. Read this article from Notebookcheck to read PWM in detail.

Check out the PWM of any display from this link.

Advantages:

  • The brightness can be lowered to less than 1% without degrading the colors of the display.
  • Wide Dimming Range and more control over smartphone display brightness.
  • Dimming Ratio of 100:1
  • Less Display sensitive means can be deployed on more display types.

Disadvantages:

  • Display Flickers at brightness lower than 100%. It can cause strain to eyes, headaches, and migraines to some people.
  • Even the PWM frequencies of over 20k are detectable by some humans.
  • Flickering gets worse on low brightness. Lower the brightness, the more the flicker of the display. The higher flicker in low brightness is the reason for the eyesight of people getting worse.
DC Dimming:

It is the oldest and simplest technique. The brightness of the smartphone display is reduced by reducing the current and vice versa. Sound pretty simple? Yes, it is, but it has more drawbacks than PWM.

Advantages:

  • No Flickering. This means no headaches, nausea, and migraines.
  • Essential for display higher refresh rates (above 60Hz) and buttery smooth experience.
  • Works perfectly in IPS LCD displays.

Disadvantages:

  • Poor Dimming Range.
  • Display minimum brightness that can be controlled easily with lowering the current is 30%. Lower than 30% and the brightness can’t be controlled. This is why PWM is used for lower brightness because it provides better control in low brightness range than DC dimming.
  • At Low brightness, the picture quality of display degrades significantly as it causes a shift in colors.
  • Dimming Ratio of 3:1

Solution: The PWM offers a better brightness control range (1%) without degrading the picture quality but it is really bad for people with sensitive eyes. DC dimming provides the natural transitions of brightness but suffers from a color shift in low brightness.

First of all, if your eyes are sensitive to PWM, do not even think about buying an OLED. There is no OLED on the market that does not use PWM. The LCDs do use PWM but they often have very high frequencies and some include DC dimming as well. Even if there is only PWM in an LCD, it is not as lethal as an OLED because of the fewer LEDs in an LCD display.

But if you must buy an OLED, buy one which has DC dimming as well as the frequency of PWM is higher than 500Hz. If you have an iPhone, this is an easy way to fix this. If not use software such as ‘OLED Saver’ from the play store for your Android.

Brightness Distribution:

Every smartphone display has different brightness zones. Each brightness zone has a different brightness than the others. The more similar the brightness of these zones, the better the brightness distribution.

Just look at the difference in the brightness of the different zones. The brightness distribution should be above 90% for a good smartphone display. You can check the brightness distribution of most smartphones from Notebookcheck.

Response Time

Response time determines how fast each pixel of a display can change from one color to the next color. The colors in question are the transition from black to white and the transition of different shades of grey.

Doesn’t matter if you have a 120Hz display with 240Hz touch sensing; if your smartphone display response time is low, you will see ghosting or the remains of the previous frame. What happens is that the next frame is loading but your display slower response time does not allow the pixels to transition fast enough.

For a 60Hz display, a frame takes 16.67ms. For a 120Hz display, it takes 8.33ms. If the response time is slower than 16.67 ms for a 60Hz display, you will get blur in your games or fast-paced movies.

The response time of some of the smartphones is given below. The average black to white response time 24.9ms and 50% grey to 80% grey is 39.5ms according to notebookcheck.

SmartphonesResponse Time
(Black to White)
Lower is Better
Response Time
(50% Grey to 80% Grey)
Lower is Better
Asus Zenfone 625.6 ms44 ms
Xiaomi Mi Note 108 ms10 ms
iPhone 11 Pro Max2.8 ms7 ms
Samsung Galaxy S20 Ultra2.8 ms9.6 ms
Google Pixel 42.4 ms 2.4 ms

All of these results are available on the Notebookcheck reviews of each of these smartphones in the display section.

Miscellaneous Factors:

There are some other factors that I take a look at but I don’t go into details for these. This is why I would like to just list and explain these briefly.

Color Temperature:

Color Temperatures are measured in degrees of Kelvin ranging from 1000 to 10000 in smartphone displays. Higher the temperature, the colder the display. The ideal temperature for a smartphone display is 6500K.

Source: Google Images

Lower temperatures represent a yellowish shade and higher temperatures represent a bluish shade. It is pretty apparent by looking at the above image that the temperature around 6500K is ideal for displays as it is neither cold or hot. I have provided the color temperatures of some of the smartphones in the table below.

SmartphoneColor Temperature
(Ideal is 6500K)
Google Pixel 4XL6974K
Asus Zenfone 67658K
Apple iPhone 11 Pro Max6897K
Samsung Galaxy S10+6632K
OnePlus 7T7214K
Source: PhoneArena

Viewing Angles:

When you look at your smartphone from an angle (from the left, right or up, down side of the phone), there is a slight shift in brightness as well as the colors of the smartphone display. The smaller the color change from an angle, the better the display quality.

The viewing angle is usually checked on a 30-degree angle. The Samsung S20 has a 30% brightness decrease at an angle of 30-degree and a color shift delta of 0.0137 which is good but not amazing according to DisplayMate.

Source: NotebookCheck

Sources to Check Display Quality:

These are some of the sources I found on the internet that you can use to check the quality of a display.

Display Tests:

Test 1
https://www.eizo.be/monitor-test/

Test 2
http://www.lagom.nl/lcd-test/

Test 3
http://www.displaymate.com/check.html

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Anas Abdullah

Tech Enthusiast, Content Writer, Part-time Gamer.

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