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Quato Intelli Proof 262/240 excellence The visual contract proofer´s White Paper on wide color gamut technology Since the beginning of hardware calibration, the display calibration technology made a great leap forward. Today, standard gamut hardware calibrated TFTs are a common tool for all graphic and photographic professionals. But with the more demanding printing technologies like Multicoloror printing and the high end digital backs, the display technology needs new answers to the basic problem of the match between additive and additive/subtractive color. The Intelli Proof excellence and the incorporated Gamut Plus Technology are Quato´s answer to this technological challenge. For the first time, a display tries to cover the majority of the ECI-RGB working space that is regulated as the ISO standard working space for all graphic arts, prepress and photographic environments: plus it covers Adobe-RGB. But using the right gamut shape and size is only a small part of the work that has to be done to create one of the most powerful visual systems in the world. This whitepaper would like to give a short look behind the scenes and offers some ground braking news for all color power users: the visual contract proofing is possible. At Quato, we take the challenge to develop the most sophisticated hard- and software solution by combining powerful 255Red
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Quato Intelli Proof 262/240 excellence - pixl.dk · Quato Intelli Proof 262/240 excellence The visual contract proofer´s White Paper on wide color gamut technology Since the beginning

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Page 1: Quato Intelli Proof 262/240 excellence - pixl.dk · Quato Intelli Proof 262/240 excellence The visual contract proofer´s White Paper on wide color gamut technology Since the beginning

Quato Intelli Proof 262/240 excellence

The visual contract proofer´s White Paper on wide color gamut technology

Since the beginning of hardware calibration, the display calibration technology made a great leap forward. Today,standard gamut hardware calibrated TFTs are a common tool for all graphic and photographic professionals. Butwith the more demanding printing technologies like Multicoloror printing and the high end digital backs, the displaytechnology needs new answers to the basic problem of the match between additive and additive/subtractive color.

The Intelli Proof excellence and the incorporated Gamut Plus Technology are Quato´s answer to this technologicalchallenge. For the first time, a display tries to cover the majority of the ECI-RGB working space that is regulatedas the ISO standard working space for all graphic arts, prepress and photographic environments: plus it coversAdobe-RGB.

But using the right gamut shape and size is only a small part of the work that has to be done to create one ofthe most powerful visual systems in the world. This whitepaper would like to give a short look behind the scenesand offers some ground braking news for all color power users: the visual contract proofing is possible. At Quato,we take the challenge to develop the most sophisticated hard- and software solution by combining powerful

255Red

Page 2: Quato Intelli Proof 262/240 excellence - pixl.dk · Quato Intelli Proof 262/240 excellence The visual contract proofer´s White Paper on wide color gamut technology Since the beginning

exclude colors that cannot bereproduced even in RGB.Additionally, it uses a whitepoint ofD50 and a Gamma of 1.8 (v1) or L* (v2),so it better matches the printingtechnologies with the standardized dotgain curves and the regulation forenvironmental light.

Expanding the Gamut

The best way to expand the gamutsize is by changing the spectra ofthe backlight. By combining colorscience and chemical science, it´spossible to create a phosphor setthat has a different spectra and abetter representation of the red andgreen areas.

In the chromatic and spectraldiagram, the difference is clear tobe seen: red and green have movedin the spectra and thus, the gamutsize increased. The result is a muchhigher brillance of red and green.

The Backlight

Today´s display technologies make- in most cases - use of a CCFL-backlight (Cold CathodeFluerescent Light) that illuminatesthe TFT-screen. The CCFL-tubescontain special types of phosporsto create a white light.

The majority of the TFTs can showup to 75% of the NTSC color space.While this color space is largeenough from its volume to includethe printing standards, its size andposition is not suited to reproduceall colors of the print on the screen.

That´s because, we have differentcolor models [additive color (RGB)and subtractive color (CMY)] and ageographically suboptimalposition. To include the printingstandards, the gamut of the RGB-device has to be increased a lot.

Quato´s Gamut Plus Technology

ECI-RGB vs. Adobe-RGB optimizing

Optimizing the Gamut

Increasing the gamut may not helpto increase the coverage of ansubtractive output device. Thematch between the display´s gamutand the output device´s gamut isthe main goal. The volume of the

black outlined monitor [illustration]gamut is bigger than the redoutlined monitor gamut. However,the coverage of the red one, inrespect to the output device´sgamut, is much better. Therefore,one has to differ between thegamut quantity (raw volume) andthe gamut quality (the realcongruency to an output device).

This means that a display with asmaller but optimized gamut mightbe better suited for softproofingthan a display with a larger butsuboptimal shaped gamut.

The gamut shape differs between Adobe-RGB (red oulined) and ECI-RGB - especially inthe red/orange and blue/green area. Plus,Adobe-RGB cuts off the printer´s cyan.

The working space discussion

In today´s workflows, there are twoworking space RGBs very muchcommon: Adobe-RGB and ECI-RGB.

Adobe RGB is refered to be a goodsolution for overall work, but it´snot optimized for reproducingprinted colors or softproofing.That´s because it uses 6.500K forthe Whitepoint and a Gamma of2.2. The standard of colormanagement is D50 (5.000K) andthe dot gain curve of a standardoffset print does not match gamma2.2. Once more, the shape of thegamut shows that Adobe-RGBnearly cuts off the cyan of thestandard offset printing. ECI-RGBis more and more accepted to bethe standard RGB working spaceand is submitted as ISO standard.It was built to include all printingtechnology standards and to

The right way to go

As ECI-RGB allows to reproduce theprinting standards and includes themajority of the RGB-devices, it is a goodsolution for a media-independentworkflow. Thus, a display, that coversboth, Adobe-RGB and ECI-RGB wouldbe the best solution. The Intelli Proofexcellence was designed with this inmind.

ISOcoated v2

ECI-RGB

Adobe-RGB

Intelli Proof 262 excellence

ECI-RGB

ISOcoated /dark grey)

Adobe-RGB

Page 3: Quato Intelli Proof 262/240 excellence - pixl.dk · Quato Intelli Proof 262/240 excellence The visual contract proofer´s White Paper on wide color gamut technology Since the beginning

The Backlight development

The backlight development in thepast 3 years has made a great leapforwards. From edge-lighting todirect-lighting, from 72% NTSC tomore than 100% now, the CCFL-techology today offers what wasimagined only with a LED-backlightin the past.

Quato´s first Wide Gamut TFT, theIntelli Proof 230 excellence was awell balanced ECI-RGB and Adobe-RGB optimized. This offered a quitegood match to both color spaces,but showed a less than optimalsRGB coeverage.

The successor, the Intelli Proof 260excellence was a compromisebetween sRGB, Adobe-RGB andECI-RGB. Due to the limited gamutsize of 92%, the 260 excellencewasn´t able to match ECI-RGB asgood as the original 230excellence. On the other hand, theIntelli Proof 213 excellence waspurely optimized for Adobe-RGBand sRGB to offer especiallyphotographers a perfect colorcorrection display.

With the new Intelli Proof 240 and262 excellence, the gamut volumeincreased to 103%. This extendedwide gamut gives the real chanceto get an even better colormatching to the three commoncolor spaces. Both new units offertherefore a nearby 100% Adobe-RGB match and the ECI-RGB matchis high enough to pass the UGRArecommendation of 90%.

Gamut mythology Part 1:match vs. volume

The discrepancy between gamutvolume (quantity) and the realmatch (quality) is because it´s veryhard to reach the same primarycolors as NTSC/ECI with today´stechnology - might it be CCFL orLED. Therefore the volume that isexpressed in marketing materialdoes not really tell anything,because it´s very likely that onlythe raw volume is mentioned. Onlythe match or gamut quality reallycounts. In the table on the right,one can see that the Intelli Proof262 excellence, for example, hasa large gamut volume of 103%NTSC, but the real match to NTSC(ECI uses the same primary colors)is 94% only. Thus, following thestandard procedure, we can claim

The Intelli Proof 240 and 262 excellence Gamut

Display Gamut quantity Gamut quantity Gamut qualityCIE1931 (volume) CIE1976 (volume) (real match)ECI Adobe sRGB ECI Adobe sRGB ECI Adobe sRGB ISOcoated v2

IP 213 excel 89% 93% 125% 99% 97% 113% 85% 91% 100% 88%IP 230 excel 92% 95% 129% 90% 89% 103% 91% 91% 94% 100%IP 260 excel 93% 97% 131% 106% 105% 122% 88% 93% 99% 99%IP 240 excel 102% 107% 144% 119% 117% 137% 93% 98% 100% 100%IP 262 excel 102% 108% 145% 119% 117% 136% 94% 98% 100% 100%

Gamut projection of the new IP 262 excel and 3D snapshot

Gamut quantity versus Gamut quality

that the display has 100% ECI and100% Adobe-RGB gamut. But, inreality it´s only 94% for ECI and99% for Adobe-RGB, respectivly.

Gamut mythology Part 2:1931 vs. 1976

The standard gamut volume iscorrelated to the CIE1931 formula.Sometimes, competitors now usethe CIE1976 formula to express thegamut volume and claim to have alarger gamut size than competitors.It´s good to be seen on the right,that with CIE1976, the gamut sizeincreases a lot and makes it hardto compare units to each other. Thementioned 103% of the Intelli Proof262 excellence increases - thanksto CIE1976 - to nearby 120%. But,that´s basically the same trick that

is used in some monitor calibrationsoftware, where DeltaE 94 insteadof DeltaE 76 is used to make thecalibration look more precisely thanit really is.

Gamut mythology Part 3:Projection vs. 3D or slicing

A gamut projection always showsthe largest dimensions of a gamut,no matter the absolute L*a*b*luminance of the colors. But, whatlooks like a 100% match, can be anoticeable deviation. Thus, only aGamut slicing or a 3D model canreally show how good two devicesor reference working space anddevice match to each other. It´shard to get an idea of the 3D-Gamuton printed paper - thus, theprojection is a compromise.

ISOcoated v2

ECI-RGB

Adobe-RGB

Intelli Proof 262 excellence

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Looking at PrePress

Using a wide gamut display hassome advantages for prepress,graphic design and printing. Onlya wide gamut display reaches alevel of color reproduction andprecision that can be compared tocontract proofing (based onstandard offset printing).

A standard gamut unit reaches, forexample, for subtractive Cyan adeltaE value of 15, while an IntelliProof excellence can reduce thiserror to about 5. This is also a bigadvantage for Remote Proofingapplications that need to have thebest possible color reproduction.

When looking at non standardizedprinting technologies like HighBody(printing with higher densities) orMulticolor printing (more than 4

colors), a wide gamut display willhave an even higher benefit.Compared to a standard Intelli Proofdisplay, the gamut of the wide gamutunit is big enough to include themajority of Pantone Hexachrome.

The same applies to HighBodyprinting, where the gamutincreases up to 20% and thereforeexceeds the abilities of a standardgamut display by far.

Especially when using spot colorsin packaging, a wide gamut unitcan help to improve the output

simulation quality. A PantoneRubin Red coated has only barelyvisible 5.5 deltaE on a wide gamutunit compared to eye-tracking 13.0deltaE on a standard gamut unit.

Looking at Photography

While not suited for printing andprepress, most photographers rely onAdobe-RGB, because it́ s the standardworking space of all professional D-SLRcameras and comes preinstalled withthe number one image editor: AdobePhotoshop.

Another reason for the use of Adobe-RGB or sRGB is the output on digitallabs that internally use sRGB for theimage development. But, the gamut ofthe mini labs is much smaller thansRGB or Adobe-RGB. So it makes nodifference if one uses ECI-RGB instead.

Additionally, the standardcommunication whitepoint for the ICCcolor management is D50. Soft boxlighting and flashes generally also use5.000K. Even more, the photo is onlyone part of the workflow and at the endof this workflow is the printed image.This print matches Gamma 1.8 - 5.000Kmuch better. Using a correspondingRGB working space enables the userto get the most out of the workflow andto avoid problems from imageconverting.

The high-end photography has alreadymoved on that path as digital backsand their software widely support ECI-RGB as the RGB working space. Theimage from the camera comes withouta specific profile (but sometimes withan embedded camera profile) and theRGB-working space can be appliedduring the development of the imagein the camera software. This gives fullcontrol over the colors and the results.

Thinking Workflow

But also for DSLR users, it´s not aproblem to change from the camera´sembedded Adobe or sRGB to ECI-RGB.The major Raw-converter softwaressupport the setup of an individual RGBworking space in the

The CCDs and color algorithms in digitalcameras have quite different colorgamuts. Interestingly, Adobe RGB is notable to reproduce the camera´s gamut- especially in the red area. ECI-RGB´soverall match to the camera´s colorabilities is much better.

But Adobe-RGB is not only used inconjunction to a camera. It́ s also usedin conjunction to photographic inkjetprinters. Interestingly, no inkjet printer- even the 12 color ones not - canreproduce the Adobe-RGB gamut.Furthermore, Adobe-RGB cuts off theCyan of the printer´s gamut. ECI-RGBoffers - once again - a better coverageof the color gamut.

The conclusion is to think about theworkflow and to use ECI-RGB plus anECI-RGB optimized wide gamut displaylike the Intelli Proof excellence.

ECI-RGB

Frontier PD

Frontier sRGB

ECI-RGB

Adobe-RGB

DSLR

Digital back

Intelli Proof excellence

Intelli Proof 230 (dark grey)

ISOcoated Offset

Pantone Hexachrome

ECI-RGB

Adobe-RGB

12 color Inkjet

8 color inkjet

Page 5: Quato Intelli Proof 262/240 excellence - pixl.dk · Quato Intelli Proof 262/240 excellence The visual contract proofer´s White Paper on wide color gamut technology Since the beginning

There are many different ways tocalibrate and profile a display. If onecan adjust the monitor’s hardwareautomatically we can call it hardware-calibration. If no adjustments arepossible or only the luminance andthe whitepoint can be controlled wewill call it software-calibration. Thegamut is only slightly affected by thistype of calibration, even if somepeople argue this way. But, the moreprecise the calibration and theprofiling process are, the better thecolor performance and the simulationof in-gamut and out of gamut colorswill be. If the color profile on the otherhand has to balance the monitor’sdrawbacks too much, then the overallquality will decrease.

Visual calibration

Without the assistance of a measuringdevice, a monitor can only be adjustedby using the human eye. Apple´sColorsync and Adobe´s Gamma allowthe user to adjust based on visual testpatterns. So this is fairly precise. Thewhitepoint can also be adjusted, butthe software never knows the state ofthe monitor.

Software calibration

A monitor without adjustments canset the luminance in most cases, butdoesn’t have any control over its

Calibration Technologies

internal RGB-values. In this case, theprofile has to do a lot of math andevery deviation from the referencehas to be corrected by the ICC-profile.Such a display for example has about7.000 Kelvin and a gamma of 2.2.For prepress appliances the profilehas to reduce whitepoint by up to2.000 K and gamma by 0.4. Thisleads into a loss of about 20 shadesper channel. This loss is visuallyrecognizeable and the usage forsoftproofing and color criticalapplications is not recommended

Hardware-assisted OSD-calibration

Some TFTs allow to adjust RGB- andluminance. Depending on themonitor’s type and manufacturermore or less 100 steps are availableto tweak the colors. With 100 stepsit’s impossible to reach exactly thecalibration target. The remainingdeviations will be corrected by theprofile with only a little loss. But don’tforget the gamma. On such a displayone will lose around 19 shades perchannel by doing the gamma-math.This loss can be avoided with adisplay that supports gamma-adjustments, but the gamma in onlyvalid for the 50% gray.

The Quato Intelli Color series allowsusers to setup the whitepoint basedon Gamma 1.8, 2.2 and L*. The

resulting deviations still have to beadapted by the profile in the end andslight deviations will show some effecton graybalance and fidelity.

Factory-based hardware-calibration

In this case, the display has a precisefactory calibration LUT and a usercalibration LUT. If the user calibratesto values near the factory LUT, then acalibration process doesn’t have totweak the user LUT too much. Butthere is always a difference betweena factory and a user calibration dueto the measurement devices used.The more the user differs from thefactory calibration, the more theprecision decreases, as the calibrationdata is calculated and not measured.This ensures basic color performanceand is not suited for highend work.

Individual hardware-calibration

In this case the gamma and whitepoint will be adjusted individually andwith up 14 bit precision inside themonitor’s LUT. The hardware-calibration sets up the complete rangeof tonal values in hardware based onactual measurements. So there is noadjustment on the graphic card’s LUT,keeping the full dynamics. This kindof individual calibration takes longerthan the Factory-based hardware-calibration but is much more precise.

Intelli Proof 262/240 excellence calibration technology in depth

16 bit per channelCalibration

Processing Unit

16 bit ColorManagement

RoutinesUSB Interface

16 b

it pe

r cha

nnel

16 bit Red LUT

ImageEnhancementUnit with 30bit

Frame Modulation

30 bit color output

16 bit Green LUT

Stabilized Luminance

16 bit Blue LUT

16 b

it on

16

bit b

asis

Gamma CorrectionWhitepoint

Color Correction

feed back channel

45min

Lum

inan

ce

Luminance Circuit

Uniformity Circuit

A

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The Intelli Proof / iColor Display calibrationtechnology is based on the individualcalibration of the monitor’s LUT with upto 42 bit precision and the exact controlof the backlight to ensure a stableluminance.

Instead of a manual adjustment withits sub optimal precision of only upto 256 steps, the iColor Displaysoftware controls the Intelli Proof’sinternal Calibration Processing Unit(CPU) and the internal LUT (ColorCorrection Table) with up to 16 bitresolution by a dedicated USB-connection. To increase the precisioneven more, the software computesall values with an absolut precisionof 16 bit (65.536 steps).

This can be compared to what wasdone during high quality drumscanning. The reprograph scannedthe image in 16 bit resolution andmade all corrections with 16 bitresolution. Later, a perfect 8 bit imagewas created. Using an 8 bit imageand doing all the correction wouldresult in a big loss and visible effects.Therefore the Intelli Proof uses a scaledown from 16 bit software precisionto 14 bit calibration and 10 bit output.

The Intelli Proof display in depth

This highest precision approacheliminates the differences betweenthe monitor’s calibration and thecalibration target. The whitepointreaches a precision of less than 0.5deltaE from target to reference.Reaching a whitepoint of 5.000K for

example, is not the same as matchingthe black body curve (the real target),as the whitepoint is only correctlymatched, if it matches the black bodycurve and not the 5.000K vector.

Other than with a software calibrateddisplay, the gradation (Gamma, L*)and the whitepoint are exactlymatched for the whole dynamic rangefrom L=0 to L=100. This ensures thatcolors and grays can be reproducedat any level without visual deviationsfrom the target. The graybalanceshows only an average deviation ofless than 1 deltaE - that´s far belowthe human eye´s recognition.

Gradations (tonal response)

The display’s image processing unit(IPU) converts any 8 bit signal fromthe digital graphics card to 10 bit.As the human eye needs more than256 shades of gray to have theperception of a smooth blendingfrom one color to the other, this 10bitoutput is needed to reproduce ultrasmooth gradiants and high dynamicimages without loosing detail.

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8bit Resolution 10bit Resolution

The vector is 5.000K

Changing the levels on the 16bit image showsno deviations, while changes on the 8bit imageshow a lot of gaps in the histogram. The gaps willresult in visible loss of detail and color fidelity.

16bit 8bit

The linear curve on the left side shows theperfect match of the Intelli Proof to the targetgradation. The left shows a software calibration.

In the past, Gamma 1.8 was referredto be the Macintosh Gamma andGamma 2.2 was refered to be thestandard PC Gamma. The Gamma isnot related to a specific platform but toa specific workflow and working space.

Gamma 1.8 for example is mostly usedin the printing and graphic arts, as itmatches the ISO compliant dot gaincurve very well, while Gamma 2.2 hasa different balance between black andwhite and therefore a shifted mid gray.

A color mode change from 1.8 GammaRGB to CMYK (ISOcoated) will result inno visible loss of the gradation. Doingthis with a Gamma 2.2 RGB will resultin a visible loss.

If one decides to use ECI-RGB as theworking space, one has to calibrate themonitor with the same setup. Amismatch between working space andmonitor profile results always in a

visible loss. For example: if the monitoris calibrated with Gamma 1.8 and 5.000K and Adobe-RGB is used as a workingspace, the shown image will have aloss of about 40 shades per channel.That´s a definitive visual loss and canbest be traced by using a uniformgraybalance from black to white.

However, it´s not possible to generalizethe use of ECI-RGB for every workingenvironment. It´s the individualworkflow that rules. But following amedia neutral path with an RGBworking space that includes all possibleoutput devices is a clever choice toavoid the most common problems.

The gradiants shows the balance between black and white and where the mid gray is located. From topto bottom: ISOcoated, Gamma 1.8, L* and Gamma 2.2. It´s good to be seen, that Gamma 1.8 matches themid gray much better than L* or Gamma 2.2. That´s why the Gamma 1.8 based ECI-RGB is prefered.

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256mb DDR II-Ram

Today´s displays suffer from several non-uniformity issues. While a luminancechange from the center to the cornersmight be acceptable, a color shift fromleft to right is most likely to beunacceptable.

While direct backlight sources - insteadof edge-lighting - can significantly reducethe luminance non-uniformity, the colorshift can not be compensated. Due tothis limitation of backlight technology,Quato has developed the ADC-circuit(Area Dimming Control) that separatesthe display into 25 independent areasand individually corrects the deviationsof every single display.

The sophisticated ADC-circuit´scorrection LUT uses a factory basedmeasurement and smoothesautomatically every of the 25 areas toits neighbouring area to avoid theoccurance of a checkerboardphenomenon.

Additionally, the sensors in the back ofthe display track temperature, luminanceand whitepoint and keep the displayadjusted to the calibration parametersand give a real-time feedback to the ADC-controller to keep the uniformity.

As a result, the display easily reaches theuniformity requirements of ISO12646-2008. Additionally, the whitepoint isstabilized and the optical drift is reduced.However, slight clouds of non uniformity(called mura) cannot be fully avoided.But, the difference to CRT and standardTFT displays is visually striking and makesthe Intelli Proof excellence 240/262 aperfect solution for high end work.

The Intelli Proof display´s uniformity

Before uniformity compensation

The Quato ADC Circuit Board

LVDS-out to the panel

32mb Flash for uniformity correction LUT

ADC uniformity correction ASIC

After uniformity compensation

Color stability improvement

Whitepoint stability improvement

LVDS-in from mainboard

Page 8: Quato Intelli Proof 262/240 excellence - pixl.dk · Quato Intelli Proof 262/240 excellence The visual contract proofer´s White Paper on wide color gamut technology Since the beginning

An LCD panel is made of differentparts. Between the polarizer on theback and the polarizer on the front,there is the glass substrate coveringthe liquid crystal cells and the RGBcolor filter to the front. The polarizerin the back has the same orientationthan the back part of liquid crystalwhile the front polarizer is aligned tothe front part of the liquid crystal.The polarized light will be bent bythe liquid crystals and passedthrough the cell. The result is thatthe light passes the crystal andleaves the cell at the opposite side.The liquid crystal looks bright.Depending on the intensity of thelight that passes the Red, Green andBlue filters with their correlated liquidcrystal package on the back (the sub-pixel), the different colors occur inan additive way (Red + Green + Blueresult in white).

A word about Contrast andBrightness (Lumiance)

The contrast and luminance valueson a data sheet do not tell anythingreal. For example a 1000:1 contrastis not used in any real world application. If the monitor is calibrated to the ISO12646 recommendation of 160cd/m2 and has ablackpoint of 0.5cd/m2, a contrast ratio of 1:320 is achieved (160/0.5=320). This is the real net or working contrast - no matterwhat values are printed on the data sheet. In addition, a viewing angle of 178° only tells that the contrast does not go lower than1:10 when the image is observed at 89° from the side. But this does not tell anything about how the colors change. And the colorchange is what really counts. The specifications of a S-IPS panel for example show the same 178° viewing angle like a A-MVAor S-PVA panel. But the color - or better: hue - change is obvious. The color difference between 0° and 30° for a pure red is DeltaE4 for the S-IPS and DeltaE 8 for the S-PVA. Given that the human eye can distinguish from DeltaE 3-5 on, a visible difference.

Panel Technology

The panel technology is another key for a perfect color representation. The Intelli Proof excellence is based on advanced S-IPS paneltechnology that offers much more stable viewing conditions than competing unit based on S-PVA panels. IPS is the only available paneltechnology on the market that offers a wide viewing angle without visible hue shifts. While the luminance of a color drops, the huebasically stays the same. With S-PVA or A-MVA panels, the luminance will stay more or less the same while the hue changes heavily. Awhite image for example, will look simply darker when viewed from the side with S-IPS, while a S-PVA will get a color change to yellow.

Panel Technology - a look behind the scenes

Illustration of IPS vs. VA optical results

Page 9: Quato Intelli Proof 262/240 excellence - pixl.dk · Quato Intelli Proof 262/240 excellence The visual contract proofer´s White Paper on wide color gamut technology Since the beginning

IPS-Technology

Panel Technology - the different panel types

TN Technology

TN is the oldest and still most widelyused LCD technology. Thanks to itsrather simple structure and ease ofmanufacturing, it is the cheapest LCDtechnology available today and iswidely used for home and officecomputer applications. TN cells havethe ability to quickly switch from darkto bright and vice versa. They alsohave some drawbacks. As can beobserved, the crystals at the edgewill not fully transition into a verticalstate when an electric signal isapplied. In addition, the opticalproperties of the TN liquid crystalsvary greatly relative to the viewingangle under which an observer looksat the screen. Heavy color and hueshifts and a poor contrast are theresult.

VA Technology (A-MVA/S-PVA)

Multidomain Vertical Alignment andPatterned Vertical Alignment areacompromise between TN and IPStechnology as the technologyresulted in fast response times,relatively good viewing angles.When one observes from the top to acell that is switched half on, thecrystals are oriented at 45 degrees andthe cell will look gray. On the otherhand, observed from the left, with aparallel viewing angle to the crystals,the cell will look dark. The cell is splitinto 2 halves (domains) in which thecrystals are oriented slightly differently,in such a way that for an observer thetwo halves work complementary. If onelooks at the screen from a differentangle, one domain will look dimmerbut this will be compensated with thesecond domain that looks equallybrighter.That´s the reason why VA-panels show a much higher color shiftat different viewing angles than IPS-panels, but offer high contrast ratios.

IPS Technology (AS-IPS/S-IPS)

In an IPS LCD display, the long axisof the crystals is always orientedparallel to the glass panels. When anelectrical signal is applied, thecrystals rotate horizontally, i.e. in thesame plane. The IPS panel needs 2electrodes to create the properelectrical field so that the liquidcrystals can rotate in a horizontalplane. As an immediate result, theaperture of each cell becomessmaller as each electrode blockssome of the light coming from thebacklight. A small aperture meansthat less polarized light can passfrom the back to the front of the

VA-Technology

TN-Technology

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display. This drawback becomesmore significant with increasingresolution (smaller cells) as therelative size of the two electrodeswill block a relatively larger part ofthe light. A display using an IPS panelwill therefore have a lower brightnessthan a TN panel when using thesame backlight. As the electrodesalso reflect some of the light, alsothe contrast ratio of IPS panels willbe somewhat lower. The majoradvantage of IPS technology is theability to preserve high contrast andcolor values under different viewingangles. For image editing, contrastpreservation is a must as there is aneed to distinguish subtle differencesfrom a broad viewing angle. And ascolor becomes more and moreimportant, accurate and repeatablecolor reproduction under differentviewing angles also becomesmandatory.

The new Intelli Proof 262 and 240excellence use an advanced S-IPSpanel that incorporates someadvantages of the hightest endmedical IPS-Pro development to offerhigh contrasts with low color shiftingand even exceeds TN/VA in respectof luminance. Thanks to theincreased transmittance of the newsubpixel structure, the new directbacklight offers a high maximumluminance of 400 cd/m2 and reducesthe overall power consumption. Ithas therefore enough headroom forbrightness aging over the time whenusing the ISO 12646 luminancerecommendation.

When comparing the new advancedS-IPS panel with a comparable 24”hardware calibrated wide gamut S-PVA unit, the known limitations of S-PVA are easy to observe. While bothdisplays look quite good from thefront, the side view shows the heavycolor shift of S-PVA. White or neutralgray areas get a reddish-yellowishcast, while the S-IPS panel simplygets darker without showing a severecolor shift. This can be seen on bothimages, the color and the black andwhite one on the right.

On the color image, especially thegray and color balance strip on theright shows a severe color shift toyellow while the image shows anoverall visible shift to yellow.

On the grayscale image, the graybalance strip on the right shows thesame severe yellow tint while themain image has an even more visibleyellow cast.

Panel Technology - the different panel types

S-IPS pixel-structure advanced S-IPS pixel-structure (derived from IPS-Pro)

S-PVA / A-MVA pixel-structure TN pixel-structure

Direct color comparison between Quato IP 240 excel and 24” S-PVA based display

S-IPS

S-PVA

S-IPS

S-PVA

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iColor Display software in depth

IColor Display establishes a completenew way ro calibrate a display. Itsstraight forward and intuitive userinterface makes the calibrationprocess a snip; even for beginnersand semi trained personal. Whenstarting up iColor Display, the usercan decide how the calibrationshould be performed: from automatichardware calibration for Intelli ProofDisplays to simple profiling fornotebook displays.

Base calibration

After the user sets the values forwhite point, gamma andluminance, the necessarycalibration procedures areautomatic without any interactionfrom the user. After the calibration,the user saves the profile and thecomplete process is completed.

iColor Display supports Gamma, L*and a real sRGB mode. Thewhitepoint can be defined in Kelvinand x/y or XYZ. Furthermore ameasured D50 L*a*b* paper whitecan also be used for the whitepointsetup to match the screen to aprintng paper without activesoftproofing.

The human eye recognizes colorsnot always the same waycolorimeters or spectrometers do.Due to that, iColor Display allowsthe user to adjust the whitepointto match two displays to each otheror to match a screen´s whitepointto the reflective paper in a D50viewing booth.

As the world’s first dedicateddisplay calibration software, iColorDisplay allows you to save theprofile in three different wayswithout the need of a recalibration.One can choose between a RGB-optimized or a perceptivlyoptimized matrix- and a LUT-profile.As only Adobe Photoshop iCS3 and4 are able to work correctly withLUT-profiles it’s not recommendedto use this kind of profile with olderapplications. Instead a matrix-profile will do the job. Additionally,five chromatic adaptions areavailable to adapt the tonalresponse to the human eye withwhitepoints other than D50.

The results and settings of analready made calibration can beeasily transferred back into thedisplay to switch between twoenvironments without a completerecalibration.

Testing and evaluation

A set of testing- and evaluation-functions are available to ensurethe best results. The primaries(Red/Green/Blue) and secondaries(Cyan/Magenta/Yellow) are usedto show the precision inside thedisplay’s gamut in deltaE. A grey-ramp is also included. For moreexperienced users, the basicvalues are also available as XYZ-values. The deviation calculationmethod uses deltaE 76 and 94.

The ugra Display Analysis andCertification Tool is built into theiColor Display software andcertifies a monitor for proofing withdifferent printing environments.

After all optimizing and evaluation,an a/b-diagram shows the gamutof the display in projection orslicing view in comparison to twoadditional profiles. Possibledeviations can be seen beforeanything gets wrong.

TFTs do not require a calibration oncea week, a monthly recalibration isenough. This means the smallestpossible interuption of the workingprocess.

As a novelty, the iColor Displaysoftware includes a site-license. Evennon Quato monitors can becalibrated with the same allgorithmas the Intelli Proof series. Thisensures a highly predictable colorworkflow for all types of displays. Toperform a calibration or profiling ofthird party display, simply choosethe appropriate calibration task.

iColor Display 3 supports a varietyof colorimeters and spectrometers:

- Eye-one pro / photo / publish- Eye-One display 1 / 2- Datacolor Spyder 2 / 3- X-Rite DTP94 / Monaco Optix XR

For the specific tasks of a wide gamutunit calibration, only the Eye-Onespectrophotometer from Rev. D onand the Quato branded DTP 94should be used. Keeping in mind,that Eye-One spectrophotometersare not perfectly suited for TFTs asthey cannot measure dark emmissiveshades with high accurancy, acolorimeter is still better suited toproduce perfect results.

iColor supports Windows XP 32 /Vista 32/64 and X 10.2 or later(except LE series: 10.5.2 minumum).

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Aside from the precision of acalibration, the gamut is also a keyfeature for excellent soft proofingresults. The Intelli Proof’s wide colorgamut advanced S-IPS panel coversthe ISOcoated reference offsetprinting gamut at around 100%according to the ugra Display AndCertification Analysis. The slightabsolute difference to ISO12647standard offset print makes themonitor a perfect companion forremote proof solution and for highquality soft proofing of standardOffset and higher Gamut printingtechnologies.

But there is always one problem withcalibrated monitors: Is the displayreally color-correct? Does it reproducecolors correctly? How precise will asoftproof be? In order to give somehelp through these daily problems,the Quato iColor Display softwareincludes the certification routines ofboth, SWOP® and ugra/fogra for fullcolor control.

The ugra Display Analysis AndCertification Tool (ugra-DACT) isbased on the color patches of thewidely accepted ugra/fogra MediaWedge. In addition to the 48 MediaWedge patches, the ugra-DACT willalso measure the calibration and thegray balance precision. Based on thegamut size, the software will usecategories like Multicolor, coated,uncoated and newspaper printing toevaluate the display´s performance.Therefore this approach does notonly measure and certify the results,it also gives recommendations for areasonable use of that specificdisplay. That´s a complete newapproach and separates the UDACTidea from other certification tasks.

The in-line SWOP® certification,together with the integrated spotcolor measurement helps to checkthe complete workflow. To certify thecalibration, the Quato SWOP® wedgewill be opened in Adobe Photoshop®

with its embedded profile. iColor thenassists the user to measure all thepatches in Adobe Photoshop® andcheck if the color setup and thecalibration match. So the SWOP®

certification does not only certify thecalibration, it certifies the colorworkflow.

The Intelli Proof displays can beactively certified all around the world.And if other standards should beapplied, it´s no problem to extendthe certification approach.

Calibration results and built-in certification

ugra UDACT certification

ugra/fogra Mediawedge

The Quato SWOP wedge

SWOP certification

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Sample certification results

The results of the UGRA Display Analysis and Certification Tool show that the Intelli Proof excellence reaches both, a very neutral gray balance and a very high profilequality. Additionally, the unit nearly reaches an exact match to the black body curve with only 0.5 deltaE and a very dark black point of 0.2 nits. Further more, the displayreaches a Softproof quality that is nearby equal to what you get out of contract proofer and can therefore be called a “visual contract proofing system”.

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TFT is between 5.600k to 6.000k.

As D50 is the standard of colorcommunication that all ICC awareapplications use, the display´shigher whitepoint has to bedownscaled to the D50 basis. Thisis called the chromatic adaption. Alinear downscale does not match thehuman eye´s tonal response curves,so a different model has bo be takeninto account. That´s where chromatic

A few steps to the perfect image

Color management is not new. In factit’s as old the human being realisedthe colors of nature and tried toreproduce them. The human eye isthe basis of all our colored emotionsand the computer display is thecentre of all decision regarding color.Due to the extension of the display’sgamut the display will step by stepbe an add-on to the classic hardcopyproof – a soft proof will be the futureway to judge color reproduction.

Keeping that in mind, one canwonder why so many workstation useold and blurred CRTs that have neverbeen calibrated. Of course, themonitor is only one piece in the colormanagement puzzle, but it’s the mostimportant visual one.

Before any discussion about anddecision for new hardware, oneshould double check the workingenvironment since color is not color.The human eye only allows us arelative and subjective recognitionof colors. Every human being has adifferent sense of a specific color.Just think about tomato red – doesyour neighbour also have the samecolor in mind. Definitely not. But it’snot only our eye and brain thatinfluences color recognition. It’s alsothe environment. The wrongsurrounding light makes thedefinition of color pretty muchimpossible. Thanks to the ISO 3664regulation one might know the rightlighting conditions: a proofing andimaging workstation must uses D50lighting. It’s quite easy to achieveD50 light in every bureau by usingGTI or JUST daylight fluorescenttubes. With only a few steps one canhave perfect lighting conditions ifone can keep direct sunlight out ofthe office. For example the PantoneColor 169 CVC viewed under D50standard light has no visibledifference to the reference. The samecolor viewed with the normal officelighting of about 2.800 Kelvin differs

up to 12.4 deltaE. Keep in mind that– generally speaking – above 3 deltaEthe human eye recognizes differencesbetween two colors. With greys iseven lower from 0.5 deltaE on.To make it a bit more complicated,the gamut of one device and anotherdevice is also not the same. Displays,cameras and scanners are workingwith the additive RGB color space.Printers usually work with thesubtractive CMYK color space.

No device reproduces colors correctlyout of the box. So this is absolutelynecessary to perfrom a calibration tohave a valid color reproduction. Tomake the conversion from RGB toCMYK easier, the color managementis based on the device independentL*a*b* color space. This kind ofconversion ensures the best matchingof colors that share the source andthe target color space. Colors that donot match have to be converted intoa shade that is inside the gamut (colorspace) and looks near the original.Color management could not be loss-free by definition, but it warrants aclear definition of what will happenwith the colors during the conversionfrom one color space to another.

Unfortunately a monitor looksdifferent at 5.000K than a viewingbooth that uses D50 lights accordingto the ISO12647 and ISO 3664standards. Extensive tests at the RITlead into the result, that if a monitorshould match a D50 viewing booth,it needs to be calibrated to a morecolder (blueish) whitepoint and theviweing box has to be dimmed downto the luminance of the screen.Basically, the booth´s luminance inLux has to be divided by Pi to get theequivalent in candela persquaremeter. Thus, for 150 cd/m2,the box has to be reduced to 450 Lux.

The native corresponding whitepointfor paper type 1 at D50 for the humaneye on a transmissive device like a

Color deviation with D50 lighting

Color deviationwith standard lighting

The native whitepoint

adaptions like Bradford or vonKriesstep in. Quato offers the user fivedifferent chromatic adaptionmethods to optimise the display´scolor performance to the colorrecognition of the human eye whenusing non D50 lighting and displaywhitepoint. Especially iColordisplay´s reference technology - thatcalibrates all monitors to one, userdefined setup - helps to integrateIntelli Proof displays into remoteproof and special proof enviroments.

With the integrated UGRA and SWOPdisplay certification, iColor displayadditionally helps to ensure a perfectcolormanagement workflow. For thefirst time ver, users can certify if thedisplay is recommended for softproofing and remote proofing.

For a perfect workflow it’s not onlynecessary to use well balancedequipment but also all softwareapplication have to speak the samelanguage. Combined withindividually profiled and calibratedinput and output devices thisensures a trouble free color managedworkflow which is the only way toreach a perfect color reproduction.

Notice the difference

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using a the recommendations forcalibration a display may has a whiteluminance of 150 cd/m2 and a blackluminance of 0.5 cd/m2. This resultsin a contrast ration of 300:1. Thedifference between realworld andfactory is obvious and shows thatonly the net contrast rules.

The ISO 12646 does not only coverthe minimum requirements forsoftproofing displays, it also coversthe viewing conditions according toISO 3664. In contrast to UDACT andSWOP, the ISO 12646 cannot becertified at the user side - this has tobe done in a laboratory and is validfor a series of monitors and not forthe individual one.

The ugra/fogra Display Analysis andCertification Tool implements someof the elements of this upcomingregulation and establishes them onthe desktop. Todays color judgementis focussed on primaries, but thereare discussions in almost everynormative institute to extend thefocus also to the graybalance. Thereason is obvious, as it is possibleto have good primaries and a badgray balance. Is the gray balanceacceptable, than the primaries arein most cases also acceptable. Thisfocus shift is the reason why iColorDisplay is performing an extensiveiterative gray balance calibration.

But the certification does not help tosetup the display´s calibrationpreference in the right way. If onetakes the final process into account(almost every image is a leastprinted) and selects therecommended ECI-RGB workingspace, then gamma 1.8 makes muchmore sense as the image does notknow on which system it runs, soharmonizing the setup is a goodthing, too.

The next thing to define is theluminance. ISO 3664 defines at least1800 Lux as the environmental lightintensity. A display´s luminance isdefined in candela per squaremeter(cd/m.). To get LUX into a relationwith candela, it must be devided byPi. So 1800 Lux is around 600 cd/m2.No proofing display can support thishigh luminance and so most of theviewing booth include an electronicdimmer to set the viewing booth

The process stability of every digitalor analogue tool highly depends onthe ability to finally trace the resultsas beeing inside the specifications.

As a result, almost everything in thedigital workflow is standardized,except the display. There is a ISOregulation for environmental lightingconditions that defines D50 as thestandard for proofing andcomparisons between colors andprints. The ISO 12647 defines theprinting technologies and theallowed deviations from thespecifications to print in anacceptable way.

Of course, there are some regulationslike ISO 13406 (display technology)and ISO 12646 (requirements for softproofing displays). The first is onlyaccepted regarding the pixel errorclass. The latter is for manufacturersonly. So both don´t have a realimpact on today´s work.

Regarding the pixel error class, Quatodecided not to follow the ISO 13406-2, because a 21.3” display with 1.92million pixels can have more than 10defective pixels and this is nothingone would accept. Therefore QuatoIntelli Proof Displays use selectedpanels and offer a much higher levelof quality. Intelli Proof 240/262displays are granted not to have anydefective pixels in the center area ofthe screen. In the outer parts of thescreen, a maximum of two defectivepixels is allowed.

The viewing angle dependencies,specified in ISO 13406, do not reallymeet the user´s demand. A viewingangle of 178° only specifies, that thecontrast is not fallen below 1:10 whenlooking from this position on thescreen. It does not tell anythingabout the color stablility. Forexample, the Intelli Proof´s panel hasa shift in the luminance instead ashift in the color when looking athigher viewing angles on the screen.The white image still appears to bewhite and colors only decrease inluminance. That matches the humaneye, as this is more critical onchromatic shifts than on luminanceshifts. In deltaE, the Intelli Proof hasa deviation of deltaE 2 at 20°, whilesome other hardware calibrated TFTsreach deviations of up to deltaE 12at the same viewing angle.

The contrast ratio is also irritating asthe real world contrast is much lowerthan factory measurement maximumcontrast ratios like 1000:1. When

Some background and calibration recommendations

down to around 450 cd/m2.Additionally, ISO 3664 defines 32Lux for the softproofing andcomparison to a printed image. 32Lux is only given in a very dark room.In most environments, it´simpossible to reduce the externallights to such a value.

The ISO 12646 draft defines aminimum luminance of 120 cd/m2.The right luminance depends on theenvironmental lighting conditions.The brighter the light, the higher theluminance. Changing the luminanceregularly due to changes in thelighting conditions is not suited.

Stable and defined lighting is a mustfor a softproof workflow.

To summarize of all the threementioned basics for calibration, oneshould use a Gamma of 1.8 for ECI1.0 or L* for ECI 2.0. The Whitepointshould be around 5.800 K whencomparing printed images with thesoftproof under D50 light and theluminance should be at least 120cd/m2.

Gamma: 1.8 or L*Whitepoint: 5.800 kLuminance: at least 120 cd/m2

The colormanagement dialogue from AdobePhotoshop® that shows the recommendedsetup for the use of Intelli Proof displays.

gray balance dependencies

Thinking Workflow means, thatthe final result of all work is a print.

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Quatographic Technology GmbHHansestrasse 47b

fon: +49-(0)531-281381fax: +49-(0)531-2813898

38112 BraunschweigGermany

url: www.quato.demail: [email protected]

fon: +49-(0)531-281381fax: +49-(0)531-2813898

38112 BraunschweigGermany

url: www.quato.demail: [email protected]