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Ambient Light vs. Display Brightness - a Few Practical Tips

 

How to fit the display brightness to the ambient brightness? Mainly it depends on the display technology - all in all, not every solution is a source of light, so not every solution is specified with the “brightness” parameter.

 

The most “complicated” are LCDs – in this case, adjusting the display brightness is intertwined with the ambient brightness. If you do not fit the proper value of the module’s brightness, you can anticipate that the content presented on the screen will be unreadable. Today, the LCDs are still the most common display solutions used to visualize data in various applications. Is it going to be forever this way?

LCDs – popular but fickle

Certainly, LCDs are all-around us – they are usually assembled in various devices that we use daily, among them: work tools, household equipment, various kiosks and totems, information carriers, or advertising media... We can list other applications within another hour.

Each of these devices sits in characteristic spaces, which differ in, e.g., the intensity of the lighting that defines one of the crucial parameters of the LCDs, that is, brightness. Unfortunately, there is no universal recipe for display brightness adjustment – each project is different, requiring an individual approach. However, it is possible to indicate approximate values of brightness for chosen applications, which might be useful in researching the appropriate LCD. Scroll to check it out:

  • about 250 cd/m2 – the typical brightness of home and office equipment; 
  • about 250 cd/m2 – the sufficient brightness for various gaming machines, which are usually located in shady rooms (e.g., casinos) so the content presented on display will be perfectly readable;
  • about 500 cd/m2 – kiosks/totems set in intensely lighted interiors, e.g., shopping centers, stations and airports, public buildings such as public offices; among them, e.g., self-checkouts, ticket machines and parking meters, information points, vending machines, etc.; 
  • at least 750 cd/m2 – advertising media set in intensely lighted interiors, e.g., shopping centers, stations and airports, public buildings such as public offices;
  • about 750 cd/m2 – the optimal brightness for chosen industrial applications, e.g., HMIs; 
  • about 1000 cd/m2 – the optimal brightness of modules installed in the vehicles; it is worth noticing that the electronics installed in the vehicles need to fulfill a range of additional requirements, e.g., the devices used in railway vehicles should be in order with EN 50155 standard;
  • at least 1000 cd/m2 – outdoor applications*.

*So long as the devices are not located in sunny spots. In such conditions, we recommend applying at least 2500 cd/m2 LCDs (solutions with extended brightness are available on, e.g., Litemax’s offer). Moreover, it is worth using LCDs with hiTNI technology, which prevents the “black blotches” on the LCDs screens caused by the temporary loosing of the liquid crystals’ primary features while exposed to solar radiation (learn more about the liquid crystals).

Get to know all LCDs on our offer – there are over 700 LCDs by reputable suppliers such as, e.g., AUO, Litemax, or Winstar.

OLED displays – reliable but costly

OLED technology is relatively “resistant” to factors that might impact the readability of presented content, e.g., the ambient brightness. The OLED display matrix comprises OLEDs, which are a source of light, so they provide an infinite contrast ratio and wide viewing angle. That is why the images presented on the OLED displays are perfectly readable, no matter it is a lighted or darkened space (learn more about OLED technology).

At present, because of the “economic” issues, the OLED displays are often used in applications that require tiny screens, that is up to 5-inch. Among them, e.g., wearables such as smartwatches, household equipment such as audio/video players or coffee machines, as well as computer accessories such as printers or scanners. You may also notice them in the industry applications as screens in portable measuring devices.

In the table, we present the parameters of chosen OLED displays by Winstar, which you can find on Unisystem’s offer:

parameter

product/type of display

WEO006448A / graphic OLED

WEA012864L / graphic OLED

WEX025664B / graphic OLED

WEG020016A / graphic OLED

WEO128128B / graphic OLED

(circular)

WEH000802A / character OLED

WEH001601B / character OLED

WEH004002A / character OLED

available color variants*

white, yellow, blue

white, yellow, blue

white, yellow, green, blue

white, yellow, blue

white, yellow

white, yellow, green, blue

white, yellow, green, blue, red

white, yellow, blue

size

0.66"

1.28"

3.12”

4.9”

1.18"

1.2"

2.25"

5.85"

resolution (for graphics OLEDs) /

characters x rows (for character OLEDs)

64x48

128x64

256x64

200x16

128x128

8x2

16x1

40x2

module type

COG

COG+PCB

COF

COB

COG

COB

COB

COB

contrast ratio

2000:1

2000:1

2000:1

2000:1

2000:1

2000:1

2000:1

2000:1

interface

6800, 8080, SPI, I2C

I2C

6800, 8080, SPI

6800/8080, SPI

6800, 8080, SPI, I2C

6800/8080, SPI

6800/8080, SPI

6800/8080, SPI

controller

SSD1306

SH1106

SSD1322

WS0010

SSD1327

WS0010

WS0010

WS0010

power supply

3 V

3/5 V

3 V

5 V

3 V

5 V

5 V

5 V

active area

13.42 x 10.06 mm

29.42 x 14.20 mm

76.778 x 19.178 mm

123.95 x 11.15 mm

30.00 x 30.00 mm

28.16 x 11.86 mm

56.95 x 5.55 mm

148.13 x 11.85 mm

outline dimensions

18.46 x 18.10 x 1.3 mm

35.50 x 32.00 x 2.66 mm

88.0 x 27.8 x 2.05 mm

182.0 x 38.5 x 9.3 mm

37.18 x 41.23 x 2.05 mm

58.0 x 32.0 x 10.0 mm

80.0 x 36.0 x 10.0 mm

182.0 x 38.5 x 9.3 mm

operating temperature

-40~80°C

-40~80°C

-40~80°C

-40~80°C

-40~80°C

-40~80°C

-40~80°C

-40~80°C

* In our shop, you can buy off-the-shelf usually two colors of OLED displays, that is white and yellow ones. If you want to get to know the lead time for other colors, please contact us.

EPDs – more and more popular eco alternative

In the case of EPDs (Electronic Paper Displays), you will not find in the datasheets the parameter called “brightness”. It is not determined as there is no backlight in the e-paper displays, so no emitted light. That is why EPDs are energy-efficient – they require only a bit of power to change the image. However, it causes some implications in access to the presented content. In the locations where there is no sufficiently intense source of light, e.g., after dark, the implementation of additional lighting is a must to guarantee the optimal readability of the images, e.g., a few LEDs.

On the market, EPDs are commonly used in a few niches. Although the consumers usually associate e-paper displays with e-readers, they can also notice them while shopping (e-paper price tags on the shelves) or traveling (e-paper timetables on the stops/platforms). Moreover, EPDs can also be used as advertising media – check out, e.g., AB1024-EGA, a variant of ACeP (Advanced Color ePaper), which provides images of seven colors: white, black, red, yellow, blue, green, and orange (learn more about color e-paper displays by E Ink).

In the table, we present the chosen EPDs by E Ink available on Unisystem’s offer:

parameter

product

ET011TT2 / circular

ED029TC1

ED057TC2

ED078KC1

ED133UT2

ED312TT2

AC133UT1/ full range of colors

size

1.1”

2.9"

5.65"

7.8"

13.3”

31.2"

13.3”

resolution

240x240

296x128

600x448

1404x1872

1600x1200

2560x1440

1600x1200

interface

SPI

SPI

SPI

SPI

SPI

SPI

równolegĹ‚y 8-bit

active area

27.96 x 27.96 mm

66.9 x 29.06 mm

114.90 x 85.80 mm

118.64 x 158.18 mm

270.40 x 202.80 mm

691.20 x 388.80

mm

270.40 x 202.80 mm

outline dimensions

34.60 x 31.80 x 0.53 mm

79.0 x 36.7 x 1.15 mm

125.40 x 99.50 x 1.166 mm

127.60 x 173.80 x 0.78 mm

285.80 x 213.65x 0.78 mm

697.20 x 402.80 x 0.805 mm

285.80 × 213.65 × 0.993/0.953 mm

 

operating temperature

0~50°C

0~50°C

0~50°C

0~50°C

0~50°C

0~50°C

15-35°C

 

In recent years, we notice a growing interest in EPDs. Still, some barriers discourage using of e-paper displays, but – what is interesting – it is not only a price. The issue that is often raised is the implementation of EPDs in the end devices – on the one hand, e.g., the assembly of the fragile modules and the other hand, e.g., the aesthetics of the refreshing content. Sometimes, due to limited resources, the company’s representatives decided to use another display technology even though they noticed the measurable benefits of EPDs. It motivated us to create two solutions based on E Ink’s EPDs. They enable using e-paper technology by companies, which might not have suitably own resources (get to know USECs and USEMs by Unisystem).

 

No doubt, due to the implementation costs, LCDs are still the most often applied display technology. What is more, the suppliers of LCDs, constantly upgrading the liquid crystals technology. Today, you can find an excellent LCD adapted to operate in harsh environments, e.g., outdoor kiosks/totems located in the public space. In such devices, you can apply, e.g., 31.5-inch P320HVN07.0 by AUO; the presented content will be perfectly readable due to adjusted parameters such as, e.g., brightness (2500 cd/m2), contrast ratio (4000:1), or viewing angle (89°/89°/89°/89°). The operating temperature of P320HVN07.0 has been estimated between -20 and 60°C so that it can be used in various weather conditions – both during scorching summer and frosty winter.

Simultaneously, we can expect that there will be other alternatives to LCDs in the coming years because each of described display technologies is developed. A few months ago, we heard about the great news: E Ink and Innolux, which specialize in different display technologies, are working on 28-inch color EPDs. Is it a promise of a revolution? Well, we will see...