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Introduction

AOC is a brand that many people might not be familiar with, so therefore a short introduction. AOCís roots lie with Admiral, founded in Chicago in 1934 and one of the first and largest producers of colour televisions in the early era of that medium. In 1967 Admiral Overseas Corporation (AOC) was established in Taiwan, the first manufacturer of colour televisions for export. Later Admiral Overseas Corporation was renamed AOC International and marketing began directly under the AOC name. In 1988 AOC added computer monitors to their line-up. Nowadays they are market leader in various countries in Asia and South America, with strong market positions in various European countries as well. They are no longer part of Admiral, but are now a subsidiary of TPV Technology, the largest manufacturer of computer displays in the world (mainly as ODM for other companies).

The q2770Pqu is one of their higher end displays, targeted at (semi) professionals. Mainly people who need the desktop real estate offered by this 27Ē QHD display, like people in finance, analysts, programmers and CAD, but also people in the graphics industry and gamers. It offers a wide range of ergonomic adjustments, excellent viewing angles and it is very energy efficient.

This review is also available in Dutch at Tweakers.net


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Versions and regions

AOC International works with three main regions:

The Americas
EMEA
Asia-Pacific

Product carrying the same model number may vary from one region to the other. There are at least two versions of the q2770Pqu: one for EMEA and one for the Americas. The product manager was not completely sure whether the Asia-Pacific region used the same version as the Americas or a third version. One thing is for sure, the version tested is the EMEA version and that version is only used in the EMEA countries. The EMEA version is advertised as using Samsung Super PLS and the Americas version is simply advertised as IPS. It may very well be that the Americas version uses a different panel, although various manufacturers have labelled AU Optronics AHVA, Samsung PLS and similar technologies as IPS before.Test results and specifications in this review may not apply to your q2770Pqu if you live outside the EMEA region.
 

 

Testing methods
 

You may have noticed by now that this isnít your typical TFT Central review. Up till now all reviews were written by Simon, but this is the first review here written by Kid Jansen who has been involved in the site with other articles and content in the past. The equipment used is very similar, for instance we both use the X-Rite i1Display Pro and i1Pro. But we use different software to read the measurement data from the hardware. Furthermore, Simon mostly uses analyses made by the software, whereas I usually work with the raw xyY data and do the analysis myself in Excel and/or Matlab. You will notice some differences in the layout and content of the review as a result, but we've tried to make it as familiar as possible for our readers. Hopefully you will appreciate the additional reviews here!

Equipment overview
 

Test

Hardware

Software

All tests

XFX Radeon HD 7970 Black Edition DD

AMD Catalyst 14.4 driver

Gamma

X-Rite i1Display Pro colorimeter

ChromaPure Professional 2.5.2

Brightness and contrast

Uniformity

White balance

X-Rite i1Pro Rev D spectrophotometer

Colour gamut

Calibration

X-Rite i1Profiler 1.5.4

Display modes

N/A

PixPerAn v1.011e

Custom Resolution Utility 1.1.2

EDID

N/A

Monitor Asset Manager 2.9

Colour banding

N/A

FastPictureViewer Pro 1.9

Viewing angles

Canon EOS 600D + Sigma 17-50 f/2.8

Ghosting

PixPerAn v1.011e

Display lag

SMTT 2.5.0

Custom Resolution Utility 1.1.2

Backlight bleeding

Eizo Monitortest

Energy consumption

Voltcraft Energy Monitor 3000

Built-in speakers

N/A

Foobar2000 v1.3.2

Headphone out

Sennheiser HD 595 headphones

 

Notes
 

All tests were performed full screen at the native 2560x1440@60Hz display mode with the display connected to the graphics card by DisplayPort, unless stated otherwise. For all non-calibrated tests all OSD settings were reset to factory defaults, with the exception of the setting being tested. Except for the uniformity test and the checkerboard contrast test all the measurements with the i1Display Pro and i1Pro were performed in the centre of the screen. For the sequential contrast test and gamma test the i1Display Pro was mounted on a tripod.

 


Comparable Displays

The q2770Pqu has a few strong competitors in its class, like the Dell U2713HM and the ASUS PB278Q. For a more accurate comparison of the alternatives weíve also used the work of PRAD.de, because they tested all the selected alternatives. All the pros and cons are in comparison with the q2770Pqu.

 

Brand + (series) + model

UK price (average of lowest 10 on pricespy.co.uk on  July 16th 2014)

AOC q2770Pqu

£355.50

 

Acer B276HUL

£397.52

ASUS PB278Q

£433.01

BenQ BL2710PT

£374.36

Dell UltraSharp U2713HM

£400.91

Iiyama ProLite XB2776QS

£388.78

Iiyama ProLite XB2779QS

£400.02

Philips Brilliance 272C4QPJKAB

£383.91

Philips Brilliance 272P4QPJKEB

£441.40

 

Acer B276HUL

The B276HUL is built around some version of the LG Display LM270WQ1 IPS panel.

Pros

         Higher contrast ratio

         2x HDMI

         DisplayPort-out for daisy chaining

Cons

         Higher energy consumption

         Very high display lag

         No VGA connection

         HDMI cable not supplied with display

 

ASUS PB278Q
 

The ASUS PB278Q is a display that is very similar to the q2770Pqu. Itís build around the Samsung LTM270DL02 PLS panel, which was also used in early production of the q2770Pqu and which is very similar to the LTM270DL06 panel. It features the same Mstar MST9687D controller. They also feature the same Factory OSD and use exactly the same method to get into it. The PB278Q has the same display- and audio connections as the q2770Pqu and they are placed in the same order. Furthermore, the PB278Q also has 2x 3W stereo speakers that can playback input signals from DP, HDMI and a 3.5 mm stereo input. It is very likely that the PB278Q is also produced by TPV Tech.

 

Most notable differences are the lack of a USB-hub on the PB278Q, the difference in OSD and OSD-controls and the use of PWM controlled backlight dimming (at 240 Hz) on the PB278Q. Like the specifications, the performance is very similar. Both have a fairly mediocre performance out of the box, but perform much better when calibrated. Because of the similarities in parts and performance, the most significant differences are the lower price tag and better warranty policy on the q2770Pqu.

 

 

BenQ BL2710PT
 

The BL2710PT is built around the AU Optronics M270DAN01.0 AHVA panel. The AHVA technology is basically to AU Optronics what PLS is to Samsung; itís their take on ďIPSĒ. Like the q2770Pqu and the ASUS PB278Q the BL2710PT also uses the Mstar MST9687D controller. According to BenQ the BL2710PT is the first monitor specifically tailored for CAD/CAM design, with specific CAD/CAM and Animation modes.

Pros

         Scaler has 1:1 pixel mapping mode and simple aspect mode that maintains aspect ratio of source

         5 gamma presets

         BenQ Display Pilot allows you to predefine the Display Mode per program and partition desktop

         Ambient Light sensor

         Motion sensor for automatically turning off display when not in use

         8-bit + FRC colour depth to simulate 10-bit colour depth per channel

         On-screen labelling of OSD-controls

Cons

         Higher power consumption

         Low contrast ratio (especially in our review of the BL2710PT)

         User mode for white balance (individual RGB-controls) not working properly

 

Dell UltraSharp U2713HM
 

Probably the biggest competitor of the q2770Pqu is the Dell UltraSharp U2713HM. It is build around the LG Display LM270WQ1-SLB2/-SLC1 AH-IPS panel. The AH-IPS panel technology performs very similar to Samsungís PLS technology. A remarkable similarity between the LTM270DL06 panel in the q2770Pqu and the LM270WQ1-SLB2 panel in the U2713HM is that 5 out of the 6 CIE 1931 xy chromaticity coordinates of the primaries are identical, with only the Gy-coordinate spotting a difference. This is very uncommon, especially since these panels are from different manufacturers. It may very well be that Samsung and LG Display used the same LEDís and colour filters for these panels.

Pros

         Factory calibrated sRGB mode with a colour deviation of ∆E94 < 5

         Separate Hue and Saturation adjustments in Movie and Game modes

         On-screen labelling of OSD-controls

         Display 5:4 resolutions in native aspect ratio

         Slightly better panel uniformity

         All four USB-ports are USB 3.0
 

Cons

         No DisplayPort and HDMI-cables supplied with the screen

         Slightly higher power consumption

         Slightly higher price

         No integrated speakers

 

 

Iiyama ProLite XB2776QS
 

The XB2776QS uses an LG Display AH-IPS panel.

Pros

         Higher contrast ratio

         Scaler has 1:1 pixel mapping mode and simple aspect mode that maintains aspect ratio of source

Cons

         Mediocre performance after calibration

         High minimum brightness of 126 cd/m≤

         Vertical viewing angles rather disappointing for AH-IPS panel

         Brightness fixed at a very high 322 cd/m≤ in sRGB mode

         PWM controlled backlight dimming at 240 Hz

         No DisplayPort and HDMI-cables supplied with the screen

 

Iiyama ProLite XB2779QS
 

The XB2779QS uses a version of the LG Display LM270WQ1 AH-IPS panel. What makes this display unique in the list of alternatives is that it is the only display with a glare coating. All the other displays have an anti-glare coating. For some people this is a deal breaker, while others might see it as a clear advantage.

Pros

         Higher contrast ratio

         Much better uniformity

         Apart from brightness excellent out of the box performance

         Negligible display lag

         Scaler has 1:1 pixel mapping mode and simple aspect mode that maintains aspect ratio of source

         YCBCR support

Cons

         Very high minimum brightness of 159 cd/m≤

         High power consumption (partially due to high minimum brightness)

         Reflections with dark screen content

         HDMI and VGA cables not included

         PWM controlled backlight dimming, but at a very high frequency of 11.2 kHz (no visible flickering)

 

Philips Brilliance 272C4QPJKAB
 

The 272C4QPJKAB uses a Samsung PLS panel.               

Pros

         2x HDMI

         Scaler has 1:1 pixel mapping mode

Cons

         Stand only provides tilt adjustment, the other three (height, swivel and pivot) are not available

         Very poor out of the box performance

         PWM controlled backlight dimming at 200 Hz

         High power consumption

         No VGA connection

         Very high over-scan with video signal

 

Philips Brilliance 272P4QPJKEB
 

The 272P4QPJKEB uses a Samsung PLS panel.               

Pros

         2x HDMI

         Scaler has 1:1 pixel mapping mode

         Motion sensor for automatically dimming of the display when not in use

         Built-in webcam with microphone

         DisplayPort-out for daisy chaining

Cons

         Low contrast ratio

         Mediocre calibrated performance

         Very poor out of the box performance

         PWM controlled backlight dimming at 200 Hz

         High power consumption

         No VGA connection

         Very high over-scan with video signal

 



Specifications and Features

The following table gives detailed information about the specs of the screen:

Monitor Specifications

Size

27"WS (68 cm)

Panel Coating

Semi-glossy AG coating

Aspect Ratio

16:9

Interfaces

DL-DVI, DisplayPort 1.2, HDMI, D-sub (VGA)

Resolution

2560x 1440

Pixel Pitch

0.2331 mm

Design colour

Black bezel and base

Response Time

5ms G2G (12ms ISO)

Ergonomics

Tilt, 130mm height, pivot and swivel

Static Contrast Ratio

1000:1 (typical)
600:1 (min)

Dynamic Contrast Ratio

80 million:1

VESA Compatible

Yes, 100mm

Brightness

300 (typical)
250 (min)

Accessories

Power, DVI, DisplayPort, HDMI, VGA, audio and USB cables

Viewing Angles

178 / 178

Panel Technology

Samsung PLS

Weight

Net weight with stand: 7.76Kg

Backlight Technology

W-LED

Physical Dimensions

(WxHxD) with stand max height
642 x 426 x 244 mm

Colour Depth

16.77m (8-bit)

Refresh Rate

60Hz

Special Features

2x USB 3.0, 2x USB 2.0 ports, audio input and headphone socket, 2x 3W stereo speakers

Colour Gamut

Standard gamut
79.6% NTSC, 100 %sRGB, 79.2% Adobe RGB

 

The feature set of the q2770Pqu is nothing too spectacular, but it does cover the basics very well. More exclusive features like ambient light sensor, motion sensor, hardware calibration and uniformity correction are not featured on this display. It does however have all the common display inputs: DisplayPort, DVI, HDMI and VGA. The first three of those support the native resolution of 2560x1440 pixels and the HDMI connection also supports MHL 2.0 (1920x1080). The VGA connection supports a maximum resolution of 1920x1080 by default, but you can get it to work at the native resolution as well. Itís also nice to see that the cables for all four display connections are provided in the box, as well the USB 3.0 cable for the built-in hub and a 3.5 mm mini-jack male-male audio cable.

 

The USB hub has four ports: 2x USB 3.0 and 2x USB 2.0. One of the USB 3.0 ports is a fast charge port. The USB 3.0 ports are located at the right hand side of the back section and relatively easily accessible. The USB 2.0 ports are located at the bottom of the back section and are somewhat hard to access. The q2770Pqu also has built-in stereo speakers of 2x 3W and a 3.5 mm stereo output. Audio input can be supplied by DisplayPort, HDMI or a 3.5 mm stereo input. The stand of the display features all the common ergonomic adjustments: swivel, tilt, pivot and height adjustment. The OSD can be set to 16 different languages and offers various white balance -, gamma - and overdrive settings.

 

There are two scaling modes available in the OSD: wide (16:9) and 4:3. For the majority of resolutions the (most) appropriate mode is selected by default. There are no settings available for resolutions with a 16:10 or a 5:4 aspect ratio, nor is there support for 1:1 pixel mapping. The actual behaviour of the scaler is slightly more complex though, as can be seen in the Display Modes section. Not really a feature of the display itself, but more of the product as a whole is the 3 year warranty with on-site exchange. It is also certified as an ISO9241-307 pixel fault class I display, which is the second best rating and the same as for instance the Eizo ColorEdge CG models have.

Below is a summary of the features and connections of the screen:

 

Feature

Yes / No

Feature

Yes / No

Tilt adjust

DVI

Height adjust

HDMI

Swivel adjust

D-sub

Rotate adjust

DisplayPort

VESA compliant

Component

USB Ports

Composite

Card Reader

Audio connection

Ambient Light Sensor

HDCP Support

Touch Screen

MHL Support

Hardware calibration

Integrated Speakers

Uniformity correction

PiP / PbP



Design and Ergonomics

Above: front view, and rear view
 

Above:  side view - left

Above: side view - right

Above:  detail USB ports side

Above: connections

Above: detail display and audio connections

Above: detail power and USB connections

 

 

Build quality and workmanship
 

The exterior of the q2770Pqu is completely made out of 2 mm thick injection moulded ABS SD-0150. The construction of the stand is made from 1 and 2 mm thick sheet steel. The panel assembly has a steel chassis, as is always the case. A separate chassis for the display electronics, made out of 0.75 mm sheet steel, is fixed to the back of the panel assembly with foil tape. Shielding the electronics from interference and reducing the interference it sends out itself. Again something youíll see in most displays. These two are then sandwiched between the back case and front bezels, which click together. The workmanship on the exterior is good, but nothing special. No unevenness in surface finish, parts that donít fit together well or anything like that. The build quality does fall a bit short when it comes to the stability of the stand though. When typing the display is quite stable, but already wobbling around a little. When you bump against your desk it will definitely wobble around quite a bit. Pressing the OSD-buttons and power button will also move the display, because of flexing of the stand. All in all, the stand does not feel very sturdy.

 

 

Design
 

The display itself has a simple but sleek design, with narrow bezels and rounded corners. The bezels have a surface finish that resembles brushed aluminium (in horizontal direction), which gives them a more elegant look. In the upper right corner the model number is printed on the bezel in a very dark grey (hardly noticeable). In the lower right corner the labels of the OSD control buttons and power buttons protrude slightly from the bezel surface. Because they are not also printed they hardly stand out from the bezel. The only thing that does stand out is the silver AOC logo in the centre of the bottom bezel.
 

The width of the bezels is 19 mm, except for the bottom bezel, which is 28.5 mm wide. However, the back case extends beyond the bezels, which does make them 2 mm wider in practice. From the side the display is 22.5 mm wide at the edge and 56 mm in the centre. The bottom bezel is wider, because of the PCB for the OSD control buttons and the power button (as shown in the photo below). It does appear however that it could have been about 5 mm narrower.
 

Above: Power and OSD control buttons PCB inside bottom bezel

 

The stand does not look as sleek as the display itself. The base is quite large, measuring 244 mm in diameter. The advantage of a circular base is that itís very easy to implement the swivel adjustment with a very wide range, but a rectangular base can be much shallower and usually fits better with the design of the display, because the display is also rectangular.

 

 

Stand adjustments
 

The stand of the q2770Pqu features all the common adjustments, including pivot, which is quite rare for a display this size.

 

Height adjustment

Distance from desk to bezel in lowest setting

40 mm

Distance from desk to bezel in highest setting

164 mm

Adjustment range

124 mm

Tilt

Forward

Backward

25į

Swivel

Left

160į

Right

160į

Pivot

Portrait / Landscape modes

Yes

 
 

Above:  highest setting

Above:  lowest setting

Above:  tilt backward

Above:  tilt forward

Above:  swivel clockwise

Above:  swivel counter clockwise

Above:  highest setting in portrait

Above:  lowest setting in portrait

 

Warranty
 

Two of the most important selling arguments for this display are the warranty and service. AOC warrants that the display shall be free of any defects in both parts and workmanship for three years. If any defects do occur the faulty unit shall be replaced with another sample on-site. You can also choose to get the replacement unit and sent the faulty unit back yourself within two weeks. If these defects are already present at arrival the replacement unit will always be a new one. With older samples the replacement unit might be a refurbished unit, but unofficially youíll always get a new one, because the RMA numbers are too low for it to be profitable to maintain a swap supply.

 

If you no longer have the proof of purchase you can still claim you warranty. The three year warranty then starts three months after the manufacturing date indicated on the product. This can especially be interesting to owners of second hand units. Outside the warranty period you may still receive service from AOC, but youíll have to pay for the parts, labour and shipping yourself.

 

ISO9241-307 Class I
 

The q2770Pqu is certified as an ISO9241-307 pixel fault class I display, the same as Eizo ColorEdge CG models. Most displays are Class II, which allows twice as much separate pixel defects as well as Type 3 cluster defects.
 

Number of pixel defects allowed per million pixels (ISO9241-307:2008)

Defect class

Separate pixel defects

Cluster defects

Type 1

Type 2

Type 3

2 ∙ n3A + n3B

Type 1

Type 2

Type 3

Class 0

0

0

0

0

0

0

Class I

1

1

5

0

0

0

Class II

2

2

10

0

0

2

Class III

5

15

100

0

0

5

Class IV

50

150

500

5

5

50

 

Types of pixel defects

Type 1

Bright pixel

Always white

Type 2

Dead pixel

Always black

Type 3A

Bright subpixel

One or two, but not all three subpixels of a pixel are always on (counted separately)

Type 3B

Dead subpixel

One or two, but not all three subpixels of a pixel are always off (counted separately)

Cluster

Two or more of the aforementioned defects on separate pixels within a cluster of 5x5 pixels

 

Because the q2770Pqu has 3.6864 million pixels you can officially have your display replaced for:

 

≥4 bright pixels

≥4 dead pixels

≥10 bright subpixels

9 bright +  ≥1 dead subpixels

8 bright +  ≥3 dead subpixels

7 bright +  ≥5 dead subpixels

6 bright +  ≥7 dead subpixels

5 bright +  ≥9 dead subpixels

4 bright +  ≥11 dead subpixels

3 bright +  ≥13 dead subpixels

2 bright +  ≥15 dead subpixels

1 bright +  ≥17 dead subpixels

≥19 dead subpixels


 

Unofficially though, you can have your display replaced for any number of pixel defects of any type.

 

 
Audio and USB

For the testing of both the speakers and the headphone out audio was transferred to the display over DisplayPort and output was set to a sample frequency of 44.1 kHz and an audio bit depth of 16 bits, matching the MP3 and FLAC files used to test the audio quality.

 

The q2770Pqu has a 3.5 mm mini-jack stereo input and also accepts stereo audio over DisplayPort and HDMI. The output can be provided by either the built-in speakers or by connecting a pair of headphones to the 3.5 mm mini-jack headphone out.
 

Built-in speakers
 

The q2770Pqu has two built-in speakers from Veco, model 378G030A021. These are 3 W speakers with a 4 Ω impedance and an oval shaped diaphragm which measures 37 x 14 mm. In total they measure 53 x 17 x 14.5 mm (L x W x D). They are powered by a Texas Instruments TPA3113D2 6W/channel stereo class-D power amplifier.
 

Above:  diaphragm of speaker

 

Above:  backside of speaker showing brand, model, power output and impedance

 

Above:  the electronics on the main circuit board that drive the built-in speakers

 

The built-in speakers in the q2770Pqu really require a short break-in period. During the first test the sound was so distorted that they were really unusable. When testing the maximum energy consumption of the display, including USB and audio, the speakers were pushed past clipping. After we got the results of that test the volume was lowered and the speakers already sounded much better then. After a few more hours of playback the sound quality was re-assessed, by then they produced a quite reasonable sound. To get the most of them does require some fiddling around with the equalizer in the playback software, because the frequency response of these speakers is far from linear. But even then the sound is reasonable at best, mainly because of the lack of bass. Especially low pitched instruments will suffer from this. A bass guitar for instance almost sounds like a regular guitar, because the volume of frequencies below 350 Hz drops dramatically and below 130 Hz it doesnít produce any sound whatsoever. This causes music with prominent bass lines to sound quite horrible. Because of this, male vocals donít sound that well either, female vocals work better with these speakers, but still lack clarity.
 

At higher frequencies the speakers perform better, but up from 13.5 kHz youíll also notice a decline in volume and frequencies above 16.5 kHz canít be reproduced either. Apart from the narrow frequency response the built-in speakers also lack dynamic range. In music with a high dynamic range youíd have to choose between the hard parts clipping or the soft parts not being produced at all. Altogether the built-in speakers are the most into their own when the sound quality isnít that important, for instance with the playback of just speech or with low volume background music.

 

Headphone out
 

The headphone out was tested with a pair of Sennheiser HD 595 headphones. Thereís really nothing to complain here. I could not tell it apart from the Realtek ALC889 audio codec on my motherboard, despite knowing which was which.
 

USB
 

The q2770Pqu has a four port USB hub, built around the VIA VL811 USB 3.0 hub controller. The USB hub is built on a separate PCB. It features a USB 3.0 Standard B upstream port to connect the hub to the PC, two USB 2.0 High Speed ports, one regular USB 3.0 Super Speed port and one USB 3.0 Super Speed Fast Charge port. The USB 2.0 ports and the upstream port are located at the bottom and the two USB 3.0 ports are located at the right hand side.
 

Above: USB hub PCB

 



OSD Menu


Above: OSD control buttons

The OSD is controlled by four buttons on the underside of the bottom bezel.

 

Button (from left to right)

Function outside OSD

Function inside OSD

Auto

Input select

Exit / back

-

Clear Vision (sharpening)

Previous / decrease value

+

Volume of stereo output/speakers

Next / increase value

Menu

Open OSD

OK

 

The OSD works intuitively and has a logical categorization. Itís also more complete than most OSDís, offering three gamma modes, four overdrive modes and an automatic off timer among the basic settings youíll find in most OSDís. The control buttons do their job, but they do not work as nicely as for instance the touch controls on the Dell UltraSharp display with automatic function labelling on screen. They really do require some time to get used to and even then youíll find yourself pressing the wrong button every now and then.

Photographs of OSD


OSD ĖLuminance


OSD Ė Image Setup (only available on VGA)


OSD Ė Colour Setup


OSD Ė PictureBoost


OSD Ė OSD Setup


OSD Ė Extra


OSD Ė Exit

 

Factory OSD
 

The Factory OSD (also known as Service Menu) is a menu for the manufacturer to set up the display. As an end user there isnít really a good reason for accessing the factory OSD, except maybe the panel on timer, since the q2770Pqu doesnít support Active Power On Time over DDC/CI.

 


Factory OSD. Click for larger version
 

 

From left to right and top to bottom these settings/values have the following meaning:

 

Q2770PQU

Display model

20131030

Factory OSD version date in YYYYMMDD format

V004

Factory OSD version number

Auto Color

Heading of global gain and offset settings section

Gain

Global RGB gain settings

Offset

Global RGB offset settings

Cool Rx Gx Bx

RGB settings for white balance mode ďCoolĒ (same for other modes)

Bri 90

Default brightness for white balance mode = 90 (same for other modes)

Con 50

Default contrast for white balance mode = 50 (same for other modes)

Spread spectrum

Heading for LVDS spread spectrum clocking section

Freq

Frequency modulation in spread spectrum clocking

Amp

Amplitude modulation

DFM

Switch on/off Design For Manufacture mode

BurnIn

Switch on/off built in burn-in mode

Panel On x

Panel on time counter in hours

LTM270DL06

Panel type number

Logo

Switch on/off the display of the logo when turning on the display

Erase EEPROM

Complete reset to Factory Default Settings

 

Explanations

Auto Color: Gain / Offset
 

Gain and offset are curve adjustments, like gamma. In the simplest model the effect of each on the output is as follows:

Therefore, gain is a multiplicative modulation, offset an additive modulation and gamma a power modulation. The effect of gain is most prevalent in the highlights, offset in the shadows and gamma in the mid-tones.Because gain and offset are curve adjustments that can be set per channel, they affect both white balance and gamma of the output. The values in the Factory OSD for gain and offset are all 12 bit values (0-4095), which shows that the internal processing bit depth of the controller is 12 bits per channel (incoming signal from graphics card and panel are both 8 b/ch).

While these values can be adjusted and saved the effect seems to be locked. When you adjust any of them the word ďFailĒ appears next to ďAuto ColorĒ. Which is a shame for the real power users, because they could use some tweaking. AOC told us that the values for these settings are identical on every sample of this model. So there is no factory calibration.
 

RGB settings for white balance modes
 

These settings determine the white balance for the four white balance modes. The available range for each of these settings is 28 to 227. The reason for this range is unclear. Their value is not linked to the locked, but visible, RGB settings for each mode in the regular OSD: if you change one of the values in the Factory OSD the corresponding value in the regular OSD wonít change. But there is a relationship between their set value in the Factory OSD and the value displayed in the regular OSD:


This results in:

Like the gain and offset settings, these settings are identical on every sample of this model.
 

Spread spectrum
 

The LVDS spread spectrum clocking settings are used to reduce the EMI emission of the display, while at the same making it less susceptible to EMI emitted by other devices, by widening the bandwidth of the LVDS connection between the controller and the panel electronics. While this reduces the EMI emission at any one frequency, the total radiated energy remains the same. So while narrowband EMI sensitive devices may experience much less interference because of spread spectrum clocking, the situation for broadband EMI sensitive devices remains unchanged. The ďFreqĒ parameter sets the amount of spreading. The standard clock specified for the LTM270DL06 panel is 60.38 MHz and the maximum without spread spectrum is 65.63 MHz. So with spread spectrum the clock would be for instance 60.38 Ī 3 MHz. The ďAmpĒ parameter can be used to reduce the amplitude of the signal, therefore reducing the total radiated power.

DFM
 

Turning this on activates the Design For Manufacture mode. In this mode the AOC-logo at power on will not be shown and the display will go into power safe mode more quickly. This setting is locked by default.

BurnIn
 

Turning this on activates the built-in burn-in mode of the display: when there is no input source connected the display will automatically alternate between completely black, white, red, green and blue screens every second.

Erase EEPROM
 

This function resets all OSD and Factory OSD settings to default. It does not actually erase any of the four EEPROMís discussed at Electronics. It lets the controller read the back-up values for OSD and Factory OSD from the 24C32WP EEPROM and then write them back to the positions of the corresponding current values on that same EEPROM. Trying to use this function will result in the word ďFailĒ appearing next to Erase EEPROM. There is probably an additional sequence required to unlock the Gain / Offset, the DFM and the Erase EEPROM functions.

 


Power Consumption

In terms of power consumption the manufacturer lists 45.0W maximum usage, 18.0 "typical" usage and less than 0.5W in standby. We carried out our normal tests to establish its power consumption ourselves.

State and Brightness Setting

Manufacturer Spec (W)

Measured Power Usage (W)

Default (90%)

-

36.4

Calibrated (21%)

18.0

19.8

Maximum Brightness (100%)

45.0

38.9

Minimum Brightness (0%)

-

15.4

Standby

<0.5

0.4

 

Brightness setting

Test pattern

Power (W)

Apparent power (VA)

Power factor (cos φ)

0

Black

13.6

28.6

0.47

White

15.4

31.3

0.49

10

Black

15.6

31.6

0.49

White

17.6

35.1

0.50

20

Black

17.7

35.3

0.50

White

19.7

38.6

0.51

30

Black

20.0

39.1

0.51

White

22.0

42.3

0.52

40

Black

22.3

42.7

0.52

White

24.2

45.6

0.53

50

Black

24.7

46.7

0.53

White

26.7

50.0

0.53

60

Black

27.2

50.2

0.53

White

29.0

53.6

0.54

70

Black

29.5

54.4

0.54

White

31.3

57.6

0.54

80

Black

31.8

58.1

0.55

White

33.8

60.7

0.55

90 (factory default)

Black

34.4

60.9

0.57

White

36.4

64.1

0.57

100

Black

37.0

64.4

0.57

White

38.9

66.7

0.58

 

Calibrated to 120 cd/m≤

Black

17.9

34.6

0.51

White

19.8

37.2

0.53

 

Off

0.2

7.6

0.03

Stand-by

0.4

8.0

0.05

Maximum

48.5

79.5

0.61

 

Average increase in power consumption per brightness setting

0.235 W

Average increase in power consumption per cd/m≤ of white

0.113 W

 

The EcoModes on the q2770Pqu were not all tested separately, because all they do is change the brightness setting. Therefore there is no difference with setting the brightness to the same value in the Standard mode.

 

EcoMode

Brightness setting

Brightness locked

Standard (default mode)

90 (default value)

No

Text

20

Yes

Internet

40

Yes

Game

60

Yes

Movie

80

Yes

Sports

100

Yes

 

 

The q2770Pqu is extremely energy efficient, using about 19 W on average when calibrated to 120 cd/m≤. This is actually less than what a Dell UltraSharp U2412M uses at that brightness and about the same as what a U2312HM uses. Not bad considering the q2770Pqu offers a 77.78% larger desktop area and a 37.35% larger display area. Even at the highest brightness setting it still only uses 38 W on average. The highest measured peak in power consumption was 48.5 W with the brightness on the highest setting, displaying a completely white screen, all USB-ports in use and the built-in speakers blasting at full volume (actually pushing them past clipping).

 

Apart from the q2770Pqu being energy efficient the results of this test also clearly show that the q2770Pqu does not have a power supply with power factor correction. This is usually the case with computer hardware with a power consumption of less than 75 W, as it is not mandatory for those. The result is that the power factor is quite low, because of a leading current caused by the smoothing capacitors in the power supply. The reason the power factor increases at higher brightness settings is that under higher loads the capacitor will have a higher duty cycle. But the low power factor is nothing to get too excited about as a consumer; your energy bill wonít be higher because of it.

 


energy consumption
 


energy consumption comparison graph


Operation

Activation time
 

Although not the most interesting field of performance, it might still be relevant to some, as it can be quite a nuisance if it takes the display very long to produce an image on screen when you turn it on. The switch on time is measured from the moment you press the power button on the display to the moment you get an image on screen. Going in stand-by is measured from the moment the screen turns black to the moment the LED in the power button turns orange, which is when the monitor actually enters the stand-by mode, as could be verified by the energy monitor the display is plugged in to. Getting out of stand-by is measured from the moment you move the mouse to moment you get an image on screen. All measurements are in seconds and were performed on native resolution and frequency: 2560x1440 @ 60 Hz.

 

Display input interface

Switch on

Going in stand-by

Getting out stand-by

DisplayPort

6.9

15.9

20.4

HDMI

6.1

20.3

3.7

DVI-D (DL)

6.2

12.5

3.2

VGA

5.4

11.3

2.6

 

The results show that it the q2770Pqu around 6 second to switch on. Not particularly fast, but not extremely slow either. How long it takes for the display to go in stand-by varies greatly from one input to the other, with VGA being almost twice as fast as HDMI.

 

Getting out of stand-by takes the display around 3 seconds, with the exception of DisplayPort. When the screen enters stand-by the connection between the graphics card and display is lost (probably to save power). With DisplayPort it had trouble re-establishing that connection and once you get an image on screen youíll get a message that there was a link failure. Apparently this has to do with pin 20 being connected in the DisplayPort cable. To avoid this problem either use a cable with pin 20 not connected or turn the display off instead of using the stand-by mode.
 

Switching Input Interface
 

The time it takes to switch from one input to another has also been measured. DVI to VGA and vice versa have not been tested, because the graphics card has one DVI-D single link and one DVI-I dual link port, therefore a native output on both connections simultaneously was not possible.
 

Display input interface

End

DisplayPort

HDMI

DVI-D (DL)

VGA

Start

DisplayPort

-

3.1

3.2

2.2

HDMI

2.9

-

3.3

2.0

DVI-D (DL)

3.0

3.5

-

-

VGA

3.0

3.3

-

-




Panel and Backlighting

Panel Manufacturer

Samsung

Colour Palette

16.78 million

Panel Technology

PLS

Colour Depth

8-bit

Panel Module

LTM270DL06

Colour space

Standard gamut / sRGB

Backlighting Type

W-LED

Colour space coverage (%)

~79.6% NTSC, 100% sRGB, ~79.2% Adobe RGB

Panel Part and Colour Depth

The AOC q2770Pqu utilises a Samsung LTM270DL06 PLS (Plane to Line Switching) panel which is capable of producing 16.78 million colours. This is achieved through a true 8-bit colour depth as opposed to Frame Rate Control (FRC) being needed.

The panel is confirmed when dismantling the screen as shown:

Display Electronics

 

To verify what panel was used in the q2770Pqu the bezels and rear case were removed. Because the display did not have any backlight on hours on arrival the glue of the foil tape connecting the electronics chassis to the panel assembly (top picture below) wasnít heated yet and therefore the tape could easily be removed without tearing it. Because of this it took little effort to take a look at the display electronics.

 

panel assembly and display electronics chassis. Click for larger version

 

circuit boards from lefts to right: USB hub - power circuit - main circuit board

 


main circuit board

 

 

Once to the electronics were revealed all the connectors on the main circuit board could easily be identified, as well as most of the integrated circuits.

 

Connectors

Starting middle left in clockwise direction

         OSD controls

         USB

         Power

         LVDS Pair #1 and #2 to panel electronics

         Power to panel electronics

         Speakers

Integrated circuits

1.       GMT G1084-33

         3.3V 5A Low-Dropout Linear Regulator

2.       SKhynix H5TQ1G63EFR

         1Gb (128 MB) DDR3 RAM

         64M x 16 configuration

         Normal power consumption

         DDR3-1600 11-11-11 clock speed and timings

         Used by the controller for the frame/line buffer

3.       Texas Instruments TPA3113D2

         6W/channel stereo class-D power amplifier

         Drives the built-in speakers

4.       Anpec APW7089

         4A 26V 380kHz Asynchronous Step-Down Converter

5.       Diodes Incorporated AS7805A

         1A 3-Terminal Positive Voltage Regulator

6.       Atmel 24C32WP

         32Kb 2-Wire Serial EEPROM

         Used for:

o DP EDID

o Factory OSD current values

o Factory OSD factory defaults back-up

o Regular OSD current values

o Regular OSD factory defaults back-up

7.       Atmel 24C02WP

         2Kb 2-Wire Serial EEPROM

         Used for HDMI EDID

8.       Atmel 24C02WP

         2Kb 2-Wire Serial EEPROM

         Used for DVI-D EDID

9.       Atmel 24C02WP (the smaller one of the two ICís in the top left corner on main PCB in the second photo above)

         2Kb 2-Wire Serial EEPROM

         Used for VGA EDID


Panel Electronics

 

block diagram of the panel electronics


panel electronics


LVDS Pair #1 and #2 from main circuit board, together with the timing controllers


power from main circuit board, together with the panel electronics power circuit


These ICís probably are the Source Driver ICís

EDID

The EDID (Extended Display Identification Data) is a piece of information that tells the graphics card what display modes it supports amongst some other specifications. The EDID varies slightly per input interface. The DisplayPort EDID is displayed below.

 

Monitor

Model name............... Q2770

Manufacturer............. AOC

Plug and Play ID......... AOC2770

Serial number............ n/a

Manufacture date......... 2014, ISO week 4

Filter driver............ None

-------------------------

EDID revision............ 1.4

Input signal type........ Digital (DisplayPort)

Color bit depth.......... 8 bits per primary color

Color encoding formats... RGB 4:4:4, YCrCb 4:4:4, YCrCb 4:2:2

Screen size.............. 600 x 340 mm (27,2 in)

Power management......... Active off/sleep

Extension blocs.......... 1 (CEA-EXT)

-------------------------

DDC/CI................... Supported

MCCS revison............. 2.1

Display technology....... TFT

Controller............... Mstar 0x1600

Firmware revision........ 0.4

Active power on time..... Not supported

Power consumption........ Not supported

Current frequency........ 88,90kHz, 60,03Hz

 

Color characteristics

Default color space...... Non-sRGB

Display gamma............ 2,20

Red chromaticity......... Rx 0,660 - Ry 0,330

Green chromaticity....... Gx 0,310 - Gy 0,630

Blue chromaticity........ Bx 0,150 - By 0,040

White point (default).... Wx 0,313 - Wy 0,329

Additional descriptors... None

 

Timing characteristics

Range limits............. Not available

GTF standard............. Not supported

Additional descriptors... None

Preferred timing......... Yes

Native/preferred timing.. 2560x1440p at 60Hz (16:9)

Modeline............... "2560x1440" 241,500 2560 2608 2640 2720 1440 1443 1448 1481 +hsync +vsync

 

Standard timings supported

640 x480p at60Hz - IBM VGA

640 x480p at72Hz - VESA

640 x480p at75Hz - VESA

800 x600p at56Hz - VESA

800 x600p at60Hz - VESA

800 x600p at72Hz - VESA

800 x600p at75Hz - VESA

1024 x768p at60Hz - VESA

1024 x768p at70Hz - VESA

1024 x768p at75Hz - VESA

1280 x 1024p at75Hz - VESA

1920 x 1080p at60Hz - VESA STD

1680 x 1050p at60Hz - VESA STD

1440 x900p at60Hz - VESA STD

1280 x 1024p at60Hz - VESA STD

1280 x960p at60Hz - VESA STD

1280 x720p at60Hz - VESA STD

 

EIA/CEA-861 Information

Revision number.......... 3

IT underscan............. Supported

Basic audio.............. Supported

YCbCr 4:4:4.............. Supported

YCbCr 4:2:2.............. Supported

Native formats........... 1

Detailed timing #1....... 1920x1080p at 60Hz (16:9)

Modeline............... "1920x1080" 148,500 1920 2008 2052 2200 1080 1084 1089 1125 +hsync +vsync

Detailed timing #2....... 1280x720p at 60Hz (16:9)

Modeline............... "1280x720" 74,250 1280 1390 1430 1650 720 725 730 750 +hsync +vsync

Detailed timing #3....... 720x480p at 60Hz (16:9)

Modeline............... "720x480" 27,000 720 736 798 858 480 489 495 525 -hsync -vsync

Detailed timing #4....... 720x576p at 50Hz (16:9)

Modeline............... "720x576" 27,000 720 732 796 864 576 581 586 625 -hsync -vsync

 

CE video identifiers (VICs) - timing/formats supported

640 x480p at60Hz - Default (4:3, 1:1)

720 x480p at60Hz - EDTV (16:9, 32:27)

1920 x 1080i at60Hz - HDTV (16:9, 1:1)

1920 x 1080i at50Hz - HDTV (16:9, 1:1)

1280 x720p at60Hz - HDTV (16:9, 1:1)

1280 x720p at50Hz - HDTV (16:9, 1:1)

1920 x 1080p at50Hz - HDTV (16:9, 1:1)

720 x576p at50Hz - EDTV (16:9, 64:45)

720 x480p at60Hz - EDTV (4:3, 8:9)

720 x576p at50Hz - EDTV (4:3, 16:15)

1920 x 1080p at60Hz - HDTV (16:9, 1:1) [Native]

NB: NTSC refresh rate = (Hz*1000)/1001

 

CE audio data (formats supported)

LPCM2-channel, 16/20/24 bit depths at 32/44/48 kHz

 

CE speaker allocation data

Channel configuration.... 2.0

Front left/right......... Yes

Front LFE................ No

Front center............. No

Rear left/right.......... No

Rear center.............. No

Front left/right center.. No

Rear left/right center... No

Rear LFE................. No

 

CE vendor specific data (VSDB)

IEEE registration number. 0x000C03

CEC physical address..... 1.0.0.0

Maximum TMDS clock....... 165MHz

 

Report information

Date generated........... 17-6-2014

Software revision........ 2.90.0.1000

Data source.............. Real-time 0x1300

Operating system......... 6.1.7601.2.Service Pack 1

 

Raw data

00,FF,FF,FF,FF,FF,FF,00,05,E3,70,27,00,00,00,00,04,18,01,04,A5,3C,22,78,3A,25,95,A9,54,4F,A1,26,

0A,50,54,2F,CF,00,D1,C0,B3,00,95,00,81,80,81,40,81,C0,01,01,01,01,56,5E,00,A0,A0,A0,29,50,30,20,

35,00,80,68,21,00,00,1E,00,00,00,FC,00,51,32,37,37,30,0A,20,20,20,20,20,20,20,00,00,00,10,00,00,

00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,10,00,00,00,00,00,00,00,00,00,00,00,00,00,00,01,77,

02,03,1E,F1,4B,01,03,05,14,04,13,1F,12,02,11,90,23,09,07,07,83,01,00,00,65,03,0C,00,10,00,02,3A,

80,18,71,38,2D,40,58,2C,45,00,55,50,21,00,00,1E,01,1D,00,72,51,D0,1E,20,6E,28,55,00,55,50,21,00,

00,1E,8C,0A,D0,8A,20,E0,2D,10,10,3E,96,00,55,50,21,00,00,18,8C,0A,D0,90,20,40,31,20,0C,40,55,00,

55,50,21,00,00,18,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,00,ED
 


Screen
Coating

The screen coating on the q2770Pqu is a light, semi-glossy anti-glare (AG) offering. It retains its anti-glare properties to avoid too many unwanted reflections of a full glossy coating, but does not produce an overly grainy or dirty image that some thicker AG coatings can. There were no cross-hatching patterns visible on the coating.


Backlight Type and Colour Gamut

The screen uses a White-LED (W-LED) backlight unit which has become very popular in today's market. This helps reduce power consumption compared with older CCFL backlight units and brings about some environmental benefits as well. The W-LED unit offers a standard colour gamut which is approximately equal to the sRGB colour space. Studying the detailed panel spec sheet for DL06 panel we know that the backlight offers a 79.6% NTSC, 100.0% sRGB and 79.2% Adobe RGB coverage. Anyone wanting to work with wider colour spaces would need to consider wide gamut CCFL screens, or the newer range of GB-r-LED displays available now. If you want to read more about colour spaces and gamut then please have a read of our detailed article.


Backlight Dimming and Flicker

We tested the screen to establish the methods used to control backlight dimming. Our in depth article talks in more details about a common method used for this which is called Pulse Width Modulation (PWM). This in itself gives cause for concern to some users who have experienced eye strain, headaches and other symptoms as a result of the flickering backlight caused by this technology. We used a camera method as described in that article. This allows us to identify:

1) Whether PWM is being used to control the backlight
2) The frequency and other characteristics at which this operates, if it is used
3) Whether a flicker may be introduced or potentially noticeable at certain settings

If PWM is used for backlight dimming, the higher the frequency, the less likely you are to see artefacts and flicker. The duty cycle (the time for which the backlight is on) is also important and the shorter the duty cycle, the more potential there is that you may see flicker. The other factor which can influence flicker is the amplitude of the PWM, measuring the difference in brightness output between the 'on' and 'off' states. Please remember that not every user would notice a flicker from a backlight using PWM, but it is something to be wary of. It is also a hard thing to quantify as it is very subjective when talking about whether a user may or may not experience the side effects.

The AOC q2770Pqu uses a Direct Current (DC) method for backlight dimming and does not use PWM at all. It can therefore be classified as flicker free.

Pulse Width Modulation Used

No

Cycling Frequency

n/a

Possible Flicker at

 

100% Brightness

No

50% Brightness

No

20% Brightness

No

0% Brightness

No

For an up to date list of all flicker-free (PWM free) monitors please see our Flicker Free Monitor Database.

 


Contrast Stability and Brightness

We wanted to see how much variance there was in the screens contrast as we adjusted the monitor setting for brightness. In theory, brightness and contrast are two independent parameters, and good contrast is a requirement regardless of the brightness adjustment. Unfortunately, such is not always the case in practice. We recorded the screens luminance and black depth at various OSD brightness settings, and calculated the contrast ratio from there. Graphics card settings were left at default with no ICC profile or calibration active.

With sequential contrast black and white are not reproduced simultaneously, but one after the other, hence sequential. First you measure the brightness of a completely white screen followed by a measurement of a completely black screen. The contrast ratio is then calculated by the dividing the result of the white measurement by the result of the black measurement, as is always the case with contrast ratios. Static contrast ratio refers to sequential contrast with a constant backlight brightness, dynamic contrast ratio refers to sequential contrast with a varying backlight brightness (higher for white than for black).

 

AOC specifies a typical static contrast ratio of 1000:1. Samsung specifies the same typical static contrast ratio for the LTM270DL06 panel, with a minimum of 600:1. Both specify a typical brightness of white of 300 cd/m≤, with a minimum of 250 cd/m≤ specified by Samsung for this panel. AOC also specifies a dynamic contrast ratio of 80M:1, but one should not attach much value to numbers like these.

 

OSD Brightness

Luminance
(cd/m2)

Black Point (cd/m2)

Contrast Ratio
( x:1)

0

69.79

0.0763

914.8

5

81.77

0.0885

923.5

10

93.52

0.1013

923.0

15

105.1

0.1137

924.3

20

116.5

0.1260

924.8

25

127.7

0.1381

924.0

30

138.6

0.1503

922.4

35

149.6

0.1619

924.1

40

160.2

0.1735

923.0

45

170.8

0.1849

923.9

50

182.3

0.1973

923.8

55

192.4

0.2086

922.6

60

202.4

0.2193

923.1

65

212.2

0.2301

922.1

70

221.9

0.2410

920.8

75

231.6

0.2512

921.9

80

241.1

0.2617

921.4

85

250.3

0.2720

920.4

90

259.4

0.2818

920.4

95

268.4

0.2917

919.9

100

277.3

0.3017

919.1

 

Total Luminance Adjustment Range (cd/m2)

207.51

Brightness OSD setting controls backlight?

Total Black Point Adjustment Range (cd/m2)

0.225

Average Static Contrast Ratio

922:1

PWM Free? 

Recommended OSD setting for 120 cd/m2

22

 

All measurements were performed five times and averaged for increased accuracy. The results show that the q2770Pqu fails to achieve the specified 1000:1 contrast ratio at all brightness settings. Still, the q2770Pqu performs well here, with an average contrast of 922.1 and a calibrated contrast ratio of 906.5. The average increase in brightness per brightness setting point was 2.076 cd/m2 and the black point was 0.00226 cd/m2.

 


Luminance range of white

As the graph above shows the relation between the measured brightness for white and the brightness setting is almost perfectly linear. Any deviations here might just as well be caused by the i1Display Pro. On average the slope of the graph is 2.076 cd/m≤ / brightness setting. The brightness of the backlight is regulated through a direct current method. The q2770Pqu does not use PWM at any brightness setting to reduce the brightness.

The q2770Pqu does not achieve the specified 300 cd/m≤ for white at the highest brightness setting, but this should not be a problem for anyone, because it is far higher than the recommended brightness for most applications. Depending on the ambient lighting conditions a brightness of 100-160 cd/m≤ is recommended, with 120 cd/m≤ being the most used.


Luminance range of black


Contrast stability

The graph above shows that the contrast ratio is very stable for all brightness settings, with the lowest contrast being only 1.085% lower than the highest.
 

Simultaneous contrast I: 4x4 ANSI checkerboard

 

The required checkerboard patterns were created in Photoshop CS5 Extended and displayed in FastPictureViewer Pro 1.9.
 

With simultaneous contrast measurements black and white are reproduced simultaneously in a certain pattern. The most common pattern is the ANSI 4x4 checkerboard, which starts with black in the top left corner. The contrast ratio is then determined by dividing the average brightness of the 8 white patches by the average brightness of the 8 black patches.

Simultaneous contrast measurements give a more realistic representation of the perceived contrast with actual content. After all, most people wonít spend their time behind a computer looking at a white or black screen.

 

Average brightness white (cd/m≤)

Average brightness black (cd/m≤)

Contrast

250.0

0.2968

842.2

 

The resulting contrast is lower than the sequential contrast at the same settings. The difference can be explained by the uniformity of the panel. The contrast hardly drops because of the simultaneous rendering of both black and white.

Calibrated


The same test was also performed after calibration of the display.
 

Average brightness white (cd/m≤)

Average brightness black (cd/m≤)

Contrast

117.1

0.1354

865.4

 

Simultaneous contrast II: 16x9 checkerboard
 

To get an even more accurate representation of the real life contrast a 16x9 checkerboard was measured. Due to the size of the i1Display Pro the corners could not be measured, therefore 70 white and 70 black patches were measured.
 

Average brightness white (cd/m≤)

Average brightness black (cd/m≤)

Contrast

248.9

0.3011

826.8

 

Like with the 4x4 checkerboard the lower contrast ratio is mostly caused by the uniformity of panel.

 


Default Performance and Setup

Default settings of the screen were as follows:

Monitor OSD Option

Default Settings

Brightness

90

Contrast

50

Gamma

Gamma1

Temperature

Warm

 

We went on to test the default setup of the screen in various areas as described in the following sections.

 


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Colour Banding

 

To assess whether the q2770Pqu suffers from banding 19 gradients were examined in FastPictureViewer Pro 1.9. These were created in Photoshop CS5 Extended and saved as 16-bit uncompressed TIFF. The consequence of insufficient colour depth is colour banding:
 

Two colours that differ enough from one another to be perceived as two different colours when viewed side-by-side do not differ enough from one another to be reproduced by the display in question as two different colours.
 

Most banding we come across is the result of compression of the source, as is the case with JPEG with high compression. However, displays also cause banding themselves. By definition every display has colour banding, because the number of levels that makes up the gradient is at most equal to the horizontal resolution. To avoid any further banding the number of levels per channel has to higher than or equal to the horizontal resolution. Assuming an even number bit depth per channel that requires 12 bits per channel or higher for all common resolutions up to 4096 pixels wide.

 

That is however assuming that the gradient covers the full range of levels. A screen wide gradient that only covers a quarter of the range would require four times as many levels per channel. To avoid banding caused by colour depth altogether 16 bits per channel would suffice. With such high colour depth you could reproduce a perfectly fluent screen wide gradient on a cinema 8K (8192x4320) display that covers only one eighth of the range. Perceivable banding is mostly caused by differences in brightness across the gradient. There is only perceivable chromaticity banding with 6 bit colour depth. For chromaticity 8 bits per channel is more than enough for colour gamuts similar to the sRGB colour space. Even for the largest RGB colour spaces (with real primaries) 9 bits colour depth per channel would be more than enough, although that would be rounded up to 10, because odd numbers arenít used for colour depth. Even when the colour depth does cause more banding than the resolution, gradients may still be perceived as fluent if the colour difference between two adjacent levels is smaller than our eyes can perceive.

 

To assess whether the q2770Pqu suffers from banding 19 gradients were examined. The first 7 gradients have constant chromaticity across the gradient and differ only in brightness. The other 12 gradients vary in both brightness and chromaticity from left to right.
 

Number

Gradient

RGB value left

RGB value right

∆Y norm L→R

Banding visible

1

Black-white

[0;0;0]

[255;255;255]

1.0000

Yes

2

Black-red

[0;0;0]

[255;0;0]

0.2208

No

3

Black-green

[0;0;0]

[0;255;0]

0.7281

Yes

4

Black-blue

[0;0;0]

[0;0;255]

0.0511

No

5

Black-yellow

[0;0;0]

[255;255;0]

0.9489

Yes

6

Black-magenta

[0;0;0]

[255;0;255]

0.2719

No

7

Black-cyan

[0;0;0]

[0;255;255]

0.7792

Yes

8

White-red

[255;255;255]

[255;0;0]

-0.7792

No

9

White-green

[255;255;255]

[0;255;0]

-0.2719

No

10

White-blue

[255;255;255]

[0;0;255]

-0.9489

Yes

11

White-yellow

[255;255;255]

[255;255;0]

-0.0511

No

12

White-magenta

[255;255;255]

[255;0;255]

-0.7281

No

13

White-cyan

[255;255;255]

[0;255;255]

-0.2208

No

14

Red-green

[255;0;0]

[0;255;0]

0.5073

No

15

Red-blue

[255;0;0]

[0;0;255]

-0.1697

No

16

Green-blue

[0;255;0]

[0;0;255]

-0.6770

No

17

Yellow-magenta

[255;255;0]

[255;0;255]

-0.6770

No

18

Yellow-cyan

[255;255;0]

[0;255;255]

-0.1697

No

19

Magenta-cyan

[255;0;255]

[0;255;255]

0.5073

No

 

The results show that the 8 bit colour depth is not enough to prevent brightness banding. All gradients that show banding have a high brightness difference from left to right. Differences in chromaticity actually make it harder to see any banding on this display, otherwise gradients 8 and 12 would also have shown banding (16 and 17 probably too). Altogether the display performs here as expected. Nearly all 8 bit displays show banding with gradients 1, 3, 5 and 7. With 8 bits per channel there are only 256 combinations, which means that with a full width gradient each level is at least 10 pixels (or 2.331 mm) wide on a 2560x1440 @ 27Ē display. With those gradients the colour difference of adjacent levels is large enough for our eyes to see.

 

With 6 bit colour depth more gradients would show banding and the gradients that already show banding with 8 bit colour depth would show far more conspicuous banding. With 10 bits colour depth there might not be any perceivable banding at all, but Iíve never tested a display with native 10 bit colour depth, so I couldnít say. If a display shows more banding than expected based on the colour depth, itís most likely caused by a faulty gamma response. A calibration would probably solve that.

 

 


White Balance and Colour Temperatures

 

The white balance determines the spectral distribution (proportion of wavelengths in a colour) of all grey levels (colours with equal value for red, green and blue channels). The white balance should be equal for all grey levels; they should only differ in brightness, with that difference based on the gamma value. For displays the white balance is often specified as the Correlated Colour Temperature (CCT) in Kelvin, but this is only a one dimensional system. Around CCTís of roughly 6500 K it describes the proportion of blue and yellow. But a white point with a constant CCT can still vary along the green-magenta axis. A better way to describe the white point is based on chromaticity.

 

Many common colour spaces, among which are sRGB and Adobe RGB, use CIE Standard Illuminant D65 as white point. D65 is a standardized daylight simulator from the D-series. Itís a simulator, because its spectral distribution differs from the spectral distribution of actual sunlight. The chromaticity coordinates of D65 in the CIE 1931 xy chromaticity diagram are x = 0.31271 and y = 0.32902, the CCT is 6503.6 K. These values are often rounded off to x = 0.313, y = 0.329 and 6500 K. Nearly all display panels, including the LTM270DL06 used in the q2770Pqu, use a white point with chromaticity coordinates equal to D65. However, the display white points are not equal to D65, because they differ in spectral distribution. They are just perceptually equal and therefore metamers.

 

D65 in CIE 1931 xy chromaticity diagram

 

D65 in CIE 1976 uíví chromaticity diagram

 

White balance modes
 

The q2770Pqu has four preset white balance that can be selected from the OSD. These cannot be altered from the regular OSD, only in the Factory OSD. The values in the regular OSD are not linked to the values in the Factory OSD: if you change one of the values in the Factory OSD the corresponding value in the regular OSD wonít change, even though the white balance will in fact change. However, the values in the regular OSD are derived from the default values in the Factory OSD using the following formula:


 

The white balance for all modes is also influenced by the global Gain and Offset settings in the Factory OSD. This probably explains why the white balance in the Warm and sRGB modes, which both have equal RGB-settings, does not correspond with the native white point of the panel. For the ∆E calculations only the chromaticity was considered for all modes. The reason for this is that differences in brightness are not due to variations in white balance, but due to variations in gamma. Including the brightness values would conceal the actual accuracy of the white balance modes, because it would be hard to tell if deviations are caused by the white balance or the gamma. For both the reference and the tested value the theoretical normalized brightness was used of:

 

Where the grey level is the fractional value, for instance 10% grey is 0.10, and γ = 2.2. For the chromaticity CIE Standard Illuminant D65 was used as a reference and the tested values are obviously the measured data.

 

Warm
 

The Warm setting in the OSD is the factory default setting for the q2770Pqu. The average CCT in this mode is 6094 K and the white balance is slightly greener than a D-series illuminant of this CCT would have.
 

 

R

G

B

Value per channel in OSD

49

49

49

Value per channel in Factory OSD

125

125

125

 

Grey level

x

y

CCT (K)

∆E00

∆E94

10%

0.3097

0.3236

6720

0.49

0.44

15%

0.3182

0.3353

6179

0.84

0.83

20%

0.3197

0.3382

6093

1.49

1.42

25%

0.3205

0.3401

6050

2.11

1.95

30%

0.3216

0.3418

5993

2.74

2.50

35%

0.3219

0.3417

5978

3.01

2.75

40%

0.3219

0.3419

5977

3.36

3.04

45%

0.3218

0.3416

5980

3.55

3.21

50%

0.3218

0.3413

5985

3.72

3.36

55%

0.3213

0.3410

6006

3.87

3.47

60%

0.3211

0.3404

6018

3.91

3.52

65%

0.3209

0.3400

6029

4.01

3.61

70%

0.3205

0.3395

6051

4.03

3.62

75%

0.3202

0.3390

6066

4.03

3.63

80%

0.3197

0.3385

6091

4.01

3.60

85%

0.3194

0.3380

6110

3.97

3.57

90%

0.3188

0.3372

6141

3.83

3.45

95%

0.3181

0.3365

6180

3.62

3.27

100%

0.3168

0.3350

6252

3.08

2.78

 

Average

0.3197

0.3385

6094

3.14

2.84

 

balance of primaries in the Warm white balance mode

 

Normal
 

Despite its name the Normal mode is not the default preset in the OSD. The average CCT in this mode is 6989 K, which results in relatively cool colours (slightly blueish). Like the Warm preset the white balance is slightly greener than its D-series counterpart.
 

 

R

G

B

Value per channel in OSD

43

46

49

Value per channel in Factory OSD

113

119

125

 

Grey level

x

y

CCT (K)

∆E00

∆E94

10%

0.3024

0.3196

7211

0.89

0.86

15%

0.3009

0.3235

7246

1.65

1.31

20%

0.3064

0.3270

6876

1.20

0.90

25%

0.3051

0.3271

6948

1.79

1.29

30%

0.3071

0.3296

6808

1.98

1.32

35%

0.3063

0.3296

6854

2.48

1.65

40%

0.3066

0.3284

6850

2.27

1.56

45%

0.3060

0.3294

6875

3.00

2.00

50%

0.3060

0.3290

6881

3.11

2.09

55%

0.3058

0.3284

6893

3.17

2.16

60%

0.3051

0.3272

6946

3.30

2.34

65%

0.3051

0.3267

6956

3.35

2.43

70%

0.3046

0.3268

6985

3.81

2.72

75%

0.3041

0.3258

7025

3.96

2.92

80%

0.3043

0.3262

7007

4.11

2.99

85%

0.3040

0.3254

7034

4.20

3.16

90%

0.3031

0.3240

7106

4.52

3.56

95%

0.3028

0.3240

7121

4.82

3.75

100%

0.3015

0.3217

7232

5.29

4.37

 

Average

0.3046

0.3263

6989

3.10

2.28

 

balance of primaries in the Normal white balance mode

 

Cool
 

The Cool preset has the highest CCT, with an average value of 8683 K.
 

 

R

G

B

Value per channel in OSD

36

41

49

Value per channel in Factory OSD

100

110

125

 

Grey level

x

y

CCT (K)

∆E00

∆E94

10%

0.2882

0.3024

8601

2.37

2.24

15%

0.2846

0.3008

8959

3.71

3.42

20%

0.2867

0.3068

8594

3.96

3.56

25%

0.2888

0.3065

8435

4.40

3.98

30%

0.2879

0.3074

8484

5.01

4.43

35%

0.2886

0.3081

8404

5.35

4.70

40%

0.2876

0.3070

8518

6.07

5.27

45%

0.2878

0.3072

8494

6.50

5.59

50%

0.2867

0.3061

8611

7.21

6.13

55%

0.2876

0.3065

8533

7.44

6.31

60%

0.2867

0.3054

8639

8.12

6.81

65%

0.2860

0.3045

8721

8.73

7.25

70%

0.2858

0.3043

8742

9.18

7.56

75%

0.2854

0.3028

8828

9.80

8.01

80%

0.2855

0.3033

8798

10.07

8.18

85%

0.2855

0.3037

8787

10.38

8.38

90%

0.2849

0.3018

8906

11.12

8.88

95%

0.2848

0.3018

8911

11.44

9.09

100%

0.2834

0.2996

9113

12.36

9.67

 

Average

0.2864

0.3045

8683

7.54

6.29

 

balance of primaries in the Cool white balance mode

 

 

sRGB
 

The name of this mode may give the idea that this is a calibrated mode, that however is not the case. Out of the four presets it does come closest to D65, but the average difference is still roughly 400 K. The ∆E00 colour difference of 3.00 would be clearly visible, even without a side by side comparison.
 

 

R

G

B

Value per channel in OSD

46

46

46

Value per channel in Factory OSD

120

120

120

 

Grey level

x

y

CCT (K)

∆E00

∆E94

10%

0.3106

0.3201

6697

0.98

0.78

15%

0.3178

0.3341

6205

0.71

0.70

20%

0.3199

0.3375

6086

1.39

1.34

25%

0.3207

0.3389

6043

1.88

1.79

30%

0.3213

0.3401

6012

2.39

2.23

35%

0.3218

0.3410

5986

2.84

2.62

40%

0.3216

0.3410

5991

3.11

2.85

45%

0.3217

0.3410

5989

3.39

3.09

50%

0.3212

0.3405

6013

3.51

3.18

55%

0.3210

0.3403

6024

3.66

3.31

60%

0.3207

0.3398

6041

3.74

3.37

65%

0.3204

0.3394

6058

3.80

3.42

70%

0.3200

0.3388

6077

3.80

3.43

75%

0.3197

0.3384

6093

3.80

3.43

80%

0.3193

0.3379

6117

3.80

3.42

85%

0.3190

0.3374

6134

3.76

3.39

90%

0.3185

0.3369

6158

3.67

3.31

95%

0.3180

0.3362

6188

3.50

3.17

100%

0.3172

0.3353

6233

3.21

2.91

 

Average

0.3195

0.3376

6107

3.00

2.72

 

balance of primaries in the sRGB white balance mode

 

User
 

Unlike the other four modes this mode is not defined in the Factory OSD. The first time you start the monitor this mode will have the RGB values displayed in the table below. If you reset the OSD to factory defaults the latest values of this mode will still be saved. The only way to reset this mode is with the Erase EEPROM function in the Factory OSD, but that function is locked. Surprisingly though it does offer the best white balance, with an average CCT of 6541 K, which is very close to the desired 6504 K.

 

 

R

G

B

Value per channel in OSD

50

50

50

 

 

x

y

CCT (K)

∆E00

∆E94

10%

0.3022

0.3221

7184

0.86

0.77

15%

0.3097

0.3306

6656

0.88

0.58

20%

0.3134

0.3320

6449

0.65

0.51

25%

0.3132

0.3337

6448

1.30

0.99

30%

0.3137

0.3326

6425

0.99

0.80

35%

0.3139

0.3321

6421

0.92

0.77

40%

0.3140

0.3332

6406

1.38

1.12

45%

0.3137

0.3326

6426

1.32

1.06

50%

0.3143

0.3332

6393

1.56

1.29

55%

0.3131

0.3310

6471

0.90

0.71

60%

0.3131

0.3311

6469

1.05

0.82

65%

0.3126

0.3306

6499

1.00

0.73

70%

0.3123

0.3300

6522

0.87

0.60

75%

0.3125

0.3309

6501

1.38

1.00

80%

0.3114

0.3289

6578

0.86

0.60

85%

0.3110

0.3281

6604

0.83

0.69

90%

0.3107

0.3280

6624

1.04

0.86

95%

0.3099

0.3266

6679

1.41

1.34

100%

0.3107

0.3293

6609

1.76

1.17

 

Average

0.3119

0.3304

6541

1.10

0.86

 

balance of primaries in the User white balance mode

 

 

Gamma

 

The gamma value determines the brightness of all grey levels between black and white based on the brightness of white. The reason for gamma encoding is that human contrast perception is proportionate to brightness: you can discriminate smaller differences in brightness at a lower brightness. It would for instance be hard to distinguish between 200 and 201 cd/m≤, but the difference between 1 and 2 cd/m≤ is easily perceivable. The absolute difference is the same, but the relative difference is 200 times greater. Since display work with fixed point encoding (integers) you would have a very low relative brightness resolution near black and very high near white with linear gamma (linear relation between grey levels and brightness).

 

Example with white 100 cd/m≤ and black 0 cd/m≤

 

8-bit grey level

Brightness γ=1 (cd/m≤)

Difference (cd/m≤)

Brightness γ=2.2 (cd/m≤)

Difference (cd/m≤)

0

0

0.392

0

5.07 ∑ 10-4

1

0.392

5.07 ∑ 10-4

 

254

99.608

0.392

99.139

0.861

255

100

100

 

The difference between RGB0 and RGB1 is reduced by a factor 772 while the difference between RGB254 and RGB255 increases by a factor of 2.19, when γ=2.2 instead of γ=1.

The gamma response of the AOC q2770Pqu is tested for all three gamma settings available in the OSD (Gamma1, Gamma2 and Gamma3) and is also tested after calibration. To test the gamma response the brightness has been measured for 20 grey levels, from 5% to 100% in 5% increments. Most RGB colour spaces use a gamma of 2.2, which is also the native gamma of most display panels. Therefore a gamma of 2.2 will be used as a target value for all modes.
 

The gamma value is then obtained by

Example for 10% grey=1.53 cd/m≤ and white=263.46 cd/m≤

The target brightness is obtained by

Example for 10% grey with γ=2.2 and white=263.46 cd/m≤


Gamma1
 

The default gamma setting for the q2770Pqu is the Gamma1 mode. With an average measured gamma value of 2.29 itís the closest to the 2.2 gamma value used by many colour spaces, which is also the native gamma of the LTM270DL06 panel used in this display.
 

The largest deviations in gamma value can be found on both ends of the scale, but especially near white. The largest relative deviations in brightness can be found at the dark end of the scale. The 5% grey level stands out from the rest in that itís only measured grey level with a gamma value thatís lower than 2.2, therefore itís also the only grey level with a measured brightness higher than the target brightness. This is often the case near black and has to do with the black point of the panel: the brightness of black isnít 0 cd/m≤ and therefore grey levels near black have an offset as well. Adjusting this in the gamma curve would result in black crush.
 

Grey level

Measured brightness (cd/m≤)

Calculated gamma

Target brightness cd/m≤

Deviation from target brightness

100%

263.46

 

263.46

 

95%

232.72

2.42

235.34

-1.1%

90%

205.90

2.34

208.95

-1.5%

85%

179.47

2.36

184.26

-2.6%

80%

157.84

2.30

161.25

-2.1%

75%

136.87

2.28

139.91

-2.2%

70%

115.69

2.31

120.21

-3.8%

65%

97.08

2.32

102.12

-4.9%

60%

81.68

2.29

85.63

-4.6%

55%

66.32

2.31

70.71

-6.2%

50%

53.42

2.30

57.34

-6.8%

45%

41.53

2.31

45.48

-8.7%

40%

32.21

2.29

35.09

-8.2%

35%

23.42

2.31

26.16

-10.5%

30%

16.46

2.30

18.64

-11.7%

25%

10.86

2.30

12.48

-13.0%

20%

6.81

2.27

7.64

-10.8%

15%

3.67

2.25

4.06

-9.4%

10%

1.53

2.24

1.66

-8.2%

5%

0.60

2.03

0.36

67.0%


measured brightness for Gamma1 compared to target brightness for γ=2.2


calculated gamma for Gamma1 compared to γ=2.2


deviation in measured brightness for Gamma1 compared to target brightness for γ=2.2

 

Gamma2
 

The Gamma2 mode has a lower gamma, meaning that the brightness of the grey levels between black and white have a higher brightness. The average gamma value in this mode is 2.02, but the gamma value shows very large deviations. This mode might be useful to start from when a gamma value below 2.2 is required (for instance 1.8, used by some colour spaces), but it would definitely require a calibration.
 

Grey level

Measured brightness (cd/m≤)

Calculated gamma

Target brightness cd/m≤

Deviation from target brightness

100%

247.52

 

247.52

 

95%

219.37

2.35

221.11

-0.8%

90%

197.86

2.13

196.31

0.8%

85%

177.45

2.05

173.12

2.5%

80%

160.92

1.93

151.50

6.2%

75%

143.93

1.88

131.45

9.5%

70%

124.55

1.93

112.94

10.3%

65%

106.73

1.95

95.95

11.2%

60%

90.58

1.97

80.45

12.6%

55%

75.33

1.99

66.44

13.4%

50%

61.69

2.00

53.87

14.5%

45%

49.23

2.02

42.73

15.2%

40%

39.00

2.02

32.97

18.3%

35%

29.36

2.03

24.58

19.4%

30%

21.03

2.05

17.51

20.1%

25%

14.28

2.06

11.72

21.8%

20%

9.20

2.05

7.18

28.2%

15%

5.21

2.04

3.81

36.7%

10%

2.19

2.05

1.56

39.9%

5%

0.78

1.92

0.34

128.4%

 


measured brightness for Gamma2 compared to target brightness for γ=2.2

 


calculated gamma for Gamma2 compared to γ=2.2

 


deviation in measured brightness for Gamma2 compared to target brightness for γ=2.2

 

 

 

Gamma3
 

The Gamma3 mode has a high average gamma value of 2.48. Like in the Gamma2 mode the gamma value in the Gamma3 mode shows very large deviations. Gamma values above 2.4 are hardly used and for gamma 2.4 the Gamma1 mode is probably a better choice. Itís easier to lower the brightness through calibration than to increase it and the Gamma1 mode also has a more constant gamma value. Therefore the Gamma3 mode on the q2270Pqu isnít particularly useful.
 

Grey level

Measured brightness (cd/m≤)

Calculated gamma

Target brightness cd/m≤

Deviation from target brightness

100%

243.20

 

243.20

 

95%

210.77

2.79

217.25

-3.0%

90%

186.05

2.54

192.88

-3.5%

85%

163.27

2.45

170.09

-4.0%

80%

145.25

2.31

148.85

-2.4%

75%

123.73

2.35

129.15

-4.2%

70%

101.96

2.44

110.96

-8.1%

65%

84.57

2.45

94.27

-10.3%

60%

69.18

2.46

79.05

-12.5%

55%

55.34

2.48

65.28

-15.2%

50%

43.35

2.49

52.93

-18.1%

45%

32.61

2.52

41.98

-22.3%

40%

24.42

2.51

32.40

-24.6%

35%

16.67

2.55

24.15

-31.0%

30%

11.22

2.55

17.20

-34.8%

25%

7.07

2.55

11.52

-38.6%

20%

4.21

2.52

7.05

-40.3%

15%

2.04

2.52

3.74