A3gencolorhigh1Gernot Hoffmann CieLab-Values by W.Faust IT8.7/2 / R011220 / Ref.D50 / Brad-yes G.Hoffmann / November 27 2004 of Contents1.Introduction22.General Test Page43.IT8 Target54.CIELab / sRGB Color Chart85.CIELab / sRGB Grayscale Chart96.Grayscale Conversions127.Reflectance / Density / Visual Dot Area158.Dot Gain179.Black Generation1910.Files
20Color Printer Test PagesSettings for AcrobatEdit / Preferences / General / Page Display (since version 6)Edit / Preferences / General / Color Management (full version only)EuroscaleCoated or ISOCoated or SWOPGrayGamma 2.2: page 4 demonstrates many features for all kind of color laser, inkjet anddye sublimation printers.Especially helpful for testing a printer calibration.Printable area: page alignment and printable area are shown by three frames.Gray balance: the RGB graywedge 1 should be printed by rich black CMYK.Thiswedge is linear by numbers.At 0.5 we have Graywedge 2 (PostScript) should be printed by K-only.K is linear by numbers.: smoothness and linearity of primary inks CMY areshown top left by three wedges.Transitions of Magenta/LightMagenta and Cyan/Light Cyan for six-color-printers are also shown top left.: fully saturated colors on the fan and on the wheel.Black L=0.0 to mediumlightness L=0.5 and from L=0.5 to White L=1.0 .Hue, Lightness and Saturation aredefined by the HLS color order system.Linearly coded by numbers in sRGB.: problems with too much ink are apparent at the black end of
the rich blackgraywedge, the black parts in the photo and in the ink limit swatch 300%.
Dependingon the paper, the total ink limit should not be higher than 300% or 320%.Black generation: Undercolor Removal UCR or Gray Component Replacement GCRcan be tested.The left gray portrait is RGB coded and should be printed by richblack.The right portrait is a grayscale, converted from the RGB image by 20% dot: color photo, bottom large image.Rastered black text: text is printed by 100%, 75% and 50% K-only.Color accuracy: pages 5-7 show an IT8 scanner target: page 5 coded by sRGBpage 6 by ProPhotoRGB and page 7 coded by Lab.For sRGB some colors are out of gamut.These are marked by a dot and the RGBvalues are clipped.Load in Photoshop any page in its specific color space andmeasure RGB and Lab values.The values are colorimetrically correct but a littlerounded.Page 8 is used similarly.Gray accuracy: page 9 shows a CIELab grayscale chart, coded by sRGB.
This willbe printed mostly by K-only because of an internal interpretation of R=G=B.Page 10 shows a similar CIELab grayscale chart.B is a little modified.This pageshould be be printed always by CMYK rich black, nearly as neutral gray.Page 11 is defined as PostScript graphic with values K=0 to 100.Grayscale conversions: chapter 6.2 shows several conversions.Images 1 to 6 are grayscales, coded by 1 byte per pixel.According to chapter 8.1eachdot gain can be replaced by an equivalent gamma
.Images 7 and 8 are in CMYK withthree empty channels CMY, coded by 4 bytes per pixel.An improved workflow is explained in chapter to apply the test pages using a RIP (Raster Image Processor)RGB source spacesRGBCMYK source spaceNoneDestination spaceActual printer profileRendering IntentRelative ColorimetricThis should show all components correctly printed.CMYK is passed through withoutany change.
K-only should be printed by pure black.How to apply the test pages using PhotoshopPrinting by a RIP retains all features of the test pages.Printing by Photoshop should be done in RGB mode.The result is easily affected bywrong settings.Open document in CMYK working spaceCMYK values are correctly indicated.RGB values are converted to CMYK using theactual color spaces.This mode can be used for printing but the RGB components cannot be reproducedcorrectly.Open document in RGB working spaceRGB values and Lab values are correctly indicated.
CMYK values are converted toRGB using the actual color spaces.
K-only components appear as rich black (theThis mode can be used for printing but the CMYK components cannot be reproducedcorrectly.RGB color spacesRGBCMYK spaceEuroscale spaceActual printer profileRendering IntentRelative ColorimetricThe settings for Acrobat (Reader)sRGB / Euroscale Coated / Gray Gamma=2.2 (but
see ch.6.3)Soft proofOff4Next text 75% black: Graywedge 1 should be printed by rich black CMYK.Graywedge 2 by K-only.
Graywedge 1 hasalways a tint until the printer is accurately color calibrated.The three CMY wedges should be printed by pure inks.Next text 100% black:Source working space for RGB components was sRGB.Artefacts may appear in the PDFpreview if Smooth Line Art is enabled in Acrobat.CMYKCMYK Ink Limit 300% DotGain 20%5 CIELab-Values by W.Faust IT8.7/2 / R011220 G.Hoffmann / June 17 2007 CIELab-Values by W.Faust IT8.7/2 / R011220 G.Hoffmann / June 17 2007 by sRGB numbers / Background 118.956 CIELab-Values by W.Faust IT8.7/2 / R011220 G.Hoffmann / June 17 2007 CIELab-Values by W.Faust IT8.7/2 / R011220 G.Hoffmann / June 17 2007 by ProPhotoRGB numbers / Background 99.667 CIELab-Values by W.Faust IT8.7/2 / R011220 G.Hoffmann / June 15 CIELab-Values by W.Faust IT8.7/2 / R011220 G.Hoffmann / June 15 2007 by Lab numbers / Background L=50785-100 -90 -80 -70 -60 -50 -40 -30 -20 - -90 -80 -70 -60 -50 -40 -30 -20 - 100L* = -90 -80 -70 -60 -50 -40 -30 -20 - -90 -80 -70 -60 -50 -40 -30 -20 - 100L* = Numbers895.1
CIELab / sRGB Grayscale ChartLeft numbers in the swatches are the CIELab lightness values L=0 to 100.Rightnumbers are the sRGB values C=R=G=B=0.0 to 255.0 .The sRGB values in the file are rounded.BlackCurve for gamma-encodedvalues C=RGB for sRGBGreenLinear function, comparisonBlueCurve for values without gamma-encoding C=RGBGrayDensityGamma encoded values are indicated byThe Tone Reproduction Curve (TRC) from to C is surprisingly nearly linear0.00.10.2Bottom right:RGB graywedge, linear by / sRGB Rich Gray ChartThe gray chart on the previous page is printed eit