1

Gernot Hoffmann

CieLab-Values by W.Faust IT8.7/2 / R011220 / Ref.D50 / Brad-yes G.Hoffmann / November 27 2004 PostScript / sRGB / 709 primaries / whitepoint D65 / out of gamut marked by dot / grays equalized R=G=B

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Table of Contents

1. Introduction 2

2. General Test Page 4

3. IT8 Target 5

4. CIELab / sRGB Color Chart 8

5. CIELab / sRGB Grayscale Chart 9

6. Grayscale Conversions 12

7. Reflectance / Density / Visual Dot Area 15

8. Dot Gain 17

9. Black Generation 19

10. Files 20

Color Printer Test Pages

Settings for Acrobat

Edit / Preferences / General / Page Display (since version 6)

Custom Resolution 72 dpi

Edit / Preferences / General / Color Management (full version only)

sRGBEuroscaleCoated or ISOCoated or SWOPGrayGamma 2.2

2

Purpose: 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 R=G=B=128.Graywedge 2 (PostScript) should be printed by K-only. K is linear by numbers.

Linearity and ink transition: 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.

Saturation: 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.

Ink limit: 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% dotgain.

General appearance: 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 6.3.

1.1 Introduction

3

1.2 Introduction

How to apply the test pages using a RIP (Raster Image Processor)

RGB source space sRGB

CMYK source space None

Destination space Actual printer profile

Rendering Intent Relative Colorimetric

This 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 Photoshop

Resumed

Printing 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 space

CMYK 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 space

RGB values and Lab values are correctly indicated. CMYK values are converted toRGB using the actual color spaces. K-only components appear as rich black (theCMY channels are not empty).

This mode can be used for printing but the CMYK components cannot be reproducedcorrectly.

RGB color space sRGB

CMYK space Euroscale Coated

Grayscale Gamma=2.2

Destination space Actual printer profile

Rendering Intent Relative Colorimetric

The settings for Acrobat (Reader)

Color spaces sRGB / Euroscale Coated / Gray Gamma=2.2 (but see ch.6.3)

Soft proof Off

4

Next 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.

CMYK

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Grayscale DotGain 20%

5 CIELab-Values by W.Faust IT8.7/2 / R011220 G.Hoffmann / June 17 2007 PostScript coded by sRGB / D65 / Out of gamut marked by dot

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CIELab-Values by W.Faust IT8.7/2 / R011220 G.Hoffmann / June 17 2007 PostScript coded by sRGB / D65 / Out of gamut marked by dot

62.039.542.0

77.629.837.5

96.124.739.7

81.624.735.7

115.181.184.3

137.871.177.4

158.157.571.4

181.814.564.9

184.8163.8163.3

197.3159.8160.3

209.6155.1157.1

224.3149.5153.3

232.9235.8235.9

233.1230.8235.5

233.3235.5231.6

233.3229.8230.8

233.5229.9230.8

233.5235.6231.3

233.6230.3235.3

33.420.722.8

87.127.820.1

127.428.316.7

60.541.235.9

72.535.225.2

76.831.621.7

81.532.221.1

118.980.670.1

139.372.553.7

160.958.735.0

182.324.5

9.2

186.1164.6157.1

198.6160.6148.8

210.3157.1140.6

224.9151.3127.1

210.3231.1234.1

233.1216.9233.6

234.1233.6212.1

213.1212.3210.1

233.3212.8209.3

211.3228.8210.3

210.9212.1230.8

60.725.621.2

114.128.518.3

178.8117.9

97.966.054.242.0

72.551.429.1

81.853.222.6

75.650.523.1

152.6122.0

93.0

171.8116.6

56.5

187.6111.6

3.9

191.3109.0

0.0

198.3180.1162.8

209.3177.8146.6

218.9174.6129.3

230.6172.1108.6

185.8225.3231.8

232.1198.9230.1

235.1231.6192.5

192.1189.9187.9

231.9193.3188.8

188.6221.1190.8

189.1192.1224.9

41.425.721.9

172.688.954.9

187.3139.8118.3

58.956.042.2

60.755.728.6

68.861.223.6

62.055.723.8

150.9140.8104.8

156.6141.1

68.3

159.1142.3

17.6

161.6141.3

0.0

204.9196.9177.3

209.9196.9154.5

213.8197.1135.6

223.6198.1

0.0

157.8217.8228.3

230.1181.1226.1

236.1228.3169.6

168.8166.8164.9

229.1173.8166.8

164.3211.6169.6

166.5172.5217.8

136.170.540.0

142.9118.5

98.3

189.8153.1126.3

51.557.942.5

45.959.729.6

48.567.124.7

44.059.725.2

96.3105.5

78.8

87.5109.5

55.4

76.1114.1

26.2

71.6114.8

12.7

166.3171.3151.6

161.8173.1137.9

158.6174.9122.6

136.9182.6

66.5

127.9209.6224.3

227.1161.6220.8

237.3225.6150.1

147.5146.6144.8

225.1154.6147.3

139.3200.8149.8

144.6151.8209.1

183.180.5

0.0

145.688.533.2

183.8121.9

74.521.838.932.0

2.641.427.5

0.049.530.9

1.441.027.2

56.983.670.3

23.688.663.0

0.094.954.9

0.097.047.4

159.3171.9162.6

149.1174.6159.6

137.9177.8155.8

89.1185.6143.3

94.6200.6219.6

222.9141.6214.8

238.5221.8126.9

126.9125.4123.9

220.1134.5125.6

114.5189.6129.5

122.9131.3199.5

158.6128.1

96.5

189.3137.1

87.9

194.6149.3108.9

25.649.247.9

0.052.949.9

0.059.255.7

0.053.951.0

63.494.993.5

24.399.695.0

0.0106.8

98.6

0.0109.4102.9

156.6172.6170.3

141.1175.8172.1

125.9179.1175.3

59.9186.6178.9

47.2190.5213.8

218.5122.0208.3

239.5217.9104.6

105.8105.5104.1

214.5115.9105.6

87.8177.8110.6

101.0110.8188.8

185.5149.1104.8

187.8145.8

76.5

225.1164.3

0.029.248.054.2

0.550.563.7

0.055.775.9

0.052.270.4

68.593.5

103.3

31.796.6

117.0

0.0103.9135.1

0.0107.1150.5

155.1171.6178.8

143.8173.8186.3

127.6176.3195.8

82.9182.1213.3

0.0181.1208.3

213.1101.0201.1

240.5213.8

80.5

88.187.586.9

208.396.887.3

61.0166.5

93.3

82.390.9

178.1

192.8166.1103.8

158.6149.6128.1

173.3164.6

83.349.255.973.0

36.456.491.3

12.356.2

109.5

0.056.7

134.1

97.3102.4116.6

91.0101.9133.8

82.1102.1149.1

52.2104.0180.3

167.6168.8178.8

165.3168.9187.1

161.8169.5196.3

152.3170.3215.9

0.0170.3201.6

207.679.8

193.6

240.8209.3

53.2

68.669.068.8

202.378.968.1

20.7153.9

75.3

61.971.1

166.3

184.9178.8102.5

79.0113.5

39.5

122.4169.9112.1

37.032.253.4

37.028.970.0

35.225.890.9

12.013.4

128.8

93.586.9

105.9

96.584.5

121.5

97.081.0

137.3

95.972.6

173.3

173.1167.5179.1

174.9166.1186.9

176.8164.1196.5

179.8161.6216.3

0.0159.1194.1

201.155.5

185.3

241.3203.9

0.0

51.252.052.2

195.159.248.7

0.0140.6

57.2

42.951.7

154.1

120.5174.8130.3

0.091.024.2

11.943.525.3

69.948.469.5

85.640.284.1

97.026.199.3

101.618.1

105.8

118.095.4

115.5

132.387.9

129.8

144.878.9

142.6

176.345.0

178.3

180.8164.5178.5

190.8161.1186.3

198.1155.9194.6

216.3145.3215.1

0.0146.8185.8

193.620.1

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241.1197.6

0.0

34.935.936.4

186.836.730.2

0.0125.8

40.9

26.832.0

141.1

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12.638.534.2

5.242.550.7

62.239.250.0

77.528.751.9

94.924.760.9

80.524.752.7

114.580.895.9

138.170.9

100.5

159.853.2

104.4

179.60.0

109.3

185.6163.6171.8

196.3159.5174.3

207.8155.1177.8

223.6146.8182.1

0.0132.5176.3

183.80.0

164.3

239.9188.9

0.0

20.221.322.2

176.32.39.6

0.0108.4

23.7

14.18.6

126.8

15.820.323.6

23.819.726.6

45.223.932.5

235.3235.3235.3

217.3217.3217.3

205.6205.6205.6

194.3194.3194.3

183.9183.9183.9

172.6172.6172.6

160.5160.5160.5

149.3149.3149.3

138.3138.3138.3

128.8128.8128.8

117.1117.1117.1

107.4107.4107.4

97.597.597.5

87.587.587.5

78.478.478.4

67.667.667.6

59.459.459.4

51.051.051.0

42.542.542.5

34.734.734.7

27.127.127.1

23.323.323.3

18.918.918.9

17.217.217.2

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Coded by sRGB numbers / Background 118.9

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6 CIELab-Values by W.Faust IT8.7/2 / R011220 G.Hoffmann / June 17 2007 PostScript coded by ProPhotoRGB / D50

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CIELab-Values by W.Faust IT8.7/2 / R011220 G.Hoffmann / June 17 2007 PostScript coded by ProPhotoRGB / D50

40.031.831.7

46.528.328.5

57.429.329.9

48.226.627.1

82.467.566.9

93.963.761.2

105.559.056.2

119.548.950.4

159.5149.1146.8

166.1147.1143.8

172.6144.5140.3

181.1141.6136.6

229.1230.6231.1

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228.6230.3226.5

226.1224.1224.9

226.3224.3224.8

228.6230.3226.1

227.3224.8229.8

21.717.717.9

51.028.718.7

77.637.419.5

39.032.527.8

43.730.221.6

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48.229.819.3

83.167.456.2

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159.8149.9141.1

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171.6145.8125.6

179.3142.6113.5

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221.5210.6225.9

225.1227.8206.1

202.8202.6200.3

215.9205.6200.1

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204.8202.8222.1

35.523.318.1

68.634.519.3

134.1105.9

83.545.241.733.0

47.040.425.3

52.242.522.7

48.239.922.2

117.4105.5

79.6

126.1103.1

54.7

135.1101.3

35.2

136.899.930.7

173.8166.6148.8

178.5165.5134.1

182.3163.3118.9

188.1162.3102.5

195.8214.3224.3

213.6192.1219.9

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42.242.025.3

47.246.723.9

42.542.223.1

123.5122.3

91.5

124.0122.5

65.9

124.4123.6

44.4

125.0122.9

35.5

186.5184.8165.3

186.8184.8144.1

187.3184.8127.9

188.1185.9

58.7

177.5203.6219.1

205.6174.3213.6

218.6221.1163.9

151.1150.3148.5

193.6165.1152.6

167.6195.6159.6

161.3157.5202.6

90.162.436.2

110.8101.4

82.9

154.8138.8112.0

39.743.033.5

36.943.926.2

40.249.525.1

36.043.723.9

78.684.965.3

73.987.450.0

69.190.536.5

67.390.632.5

149.3154.1136.6

145.6154.9124.5

142.8156.1111.9

129.6161.1

73.9

159.8192.5213.6

196.6155.3205.8

216.1217.9146.3

128.5128.3126.5

182.5146.1131.6

147.3181.8139.1

140.5135.1190.8

125.377.626.7

100.176.536.2

137.1109.6

67.422.728.124.7

19.129.122.2

20.634.525.2

18.728.822.1

53.063.955.5

45.266.550.9

38.270.546.2

31.571.541.7

147.1154.3146.8

142.1155.8144.1

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118.9162.6130.3

142.8180.8207.1

187.5136.8197.5

213.3213.6126.6

106.6106.3104.9

171.1127.3109.9

128.1167.6119.3

120.8114.0178.6

123.4111.8

83.4

146.1123.6

79.5

155.1135.8

97.428.735.535.9

24.737.437.5

24.141.741.9

22.637.938.2

62.773.974.9

54.776.576.5

47.081.479.9

39.282.683.5

147.1154.8154.1

140.6156.6156.1

135.3158.8159.3

118.1163.3163.5

125.8168.3199.5

178.5119.9188.9

210.8209.3109.5

86.486.585.4

160.6110.6

90.8

109.9153.6101.5

102.093.8

165.6

148.3134.1

93.8

146.9131.1

73.1

177.1153.1

38.230.235.040.0

27.336.247.0

26.639.756.7

25.137.052.2

65.673.582.8

58.974.994.8

54.779.9

111.5

49.082.0

126.1

147.3153.9162.1

143.6155.3169.8

138.8156.9179.5

129.1160.8198.1

111.5157.1192.3

169.3103.0179.8

208.6204.9

93.5

69.869.569.1

150.694.973.9

94.3140.6

85.9

86.375.6

153.1

158.9151.1

96.3

133.8131.8112.5

144.1146.9

80.941.942.254.9

41.242.569.5

40.742.584.9

40.942.7

107.4

83.083.495.5

83.083.0

110.9

82.583.3

125.0

81.584.6

156.1

153.3152.6161.9

153.5152.8170.3

153.3153.3179.6

152.6153.9200.3

97.4145.1183.8

160.387.6

170.5

205.9200.1

78.9

53.053.253.0

141.881.457.9

78.6126.9

70.8

71.058.5

139.9

158.3162.5

97.5

70.690.142.0

120.5147.8101.8

28.725.238.5

30.924.150.9

34.423.367.8

39.019.8

101.4

74.970.384.8

78.369.198.3

80.667.3

112.5

86.463.0

147.3

156.1151.8162.3

157.9151.1170.1

160.1149.8179.5

165.1148.6200.1

83.9132.6174.8

151.372.9

160.8

203.5194.5

64.5

38.939.239.2

132.568.143.0

63.9112.8

56.5

57.943.2

126.9

123.9153.1117.5

39.767.529.2

21.230.721.3

48.738.951.7

57.536.563.2

64.532.475.5

67.830.881.0

91.679.894.0

100.376.5

106.5

108.172.4

118.1

131.161.9

152.6

159.6149.8161.5

166.1148.3168.9

170.6144.8177.1

183.8139.1198.1

71.6119.6164.9

141.658.7

149.9

200.3187.9

52.2

26.726.927.2

123.355.930.5

50.097.944.4

47.229.9

113.5

28.736.529.8

20.727.525.9

23.130.537.2

40.731.736.9

47.528.237.9

58.229.744.5

48.926.738.2

83.167.576.1

96.464.179.5

109.158.082.4

120.845.285.5

161.3149.6154.9

167.3147.1157.1

174.3144.8160.3

183.8140.1164.1

60.4105.3153.8

130.844.9

137.5

195.9178.9

40.7

16.716.917.5

112.944.719.7

37.581.532.7

38.218.299.4

15.316.218.2

18.216.519.9

28.220.724.2

230.5230.5230.5

208.5208.5208.5

194.6194.6194.6

181.3181.3181.3

169.3169.3169.3

156.5156.5156.5

143.1143.1143.1

131.1131.1131.1

119.5119.5119.5

109.5109.5109.5

97.997.997.9

88.388.388.3

78.878.878.8

69.569.569.5

61.261.261.2

52.052.052.0

45.245.245.2

38.538.538.5

31.831.831.8

26.226.226.2

20.820.820.8

18.318.318.3

15.615.615.6

14.514.514.5

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

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Coded by ProPhotoRGB numbers / Background 99.6

6

7 CIELab-Values by W.Faust IT8.7/2 / R011220 G.Hoffmann / June 15 2007 PostScript / CIELab coded / Reference white D50

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

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CIELab-Values by W.Faust IT8.7/2 / R011220 G.Hoffmann / June 15 2007 PostScript / CIELab coded / Reference white D50

18.811.2

2.9

18.823.6

6.5

21.733.4

9.6

18.627.7

7.6

38.415.0

4.2

38.929.3

9.8

39.543.215.1

39.562.420.2

69.07.83.2

69.314.4

5.3

69.421.1

7.4

69.629.210.2

93.0-0.9-0.5

91.91.4

-2.0

92.9-1.31.6

91.51.4

-0.1

91.51.30.0

92.9-1.31.8

91.81.8

-2.0

8.46.91.2

20.127.520.3

28.541.933.9

18.88.67.2

18.917.214.9

18.721.217.2

19.722.919.2

38.415.513.0

39.027.724.5

39.742.237.2

39.759.751.0

69.37.26.9

69.413.211.8

69.518.716.7

69.626.524.6

90.1-6.7-3.9

88.47.9

-6.0

92.1-2.610.5

85.00.01.2

86.86.94.4

89.1-8.67.0

85.32.3

-9.4

14.417.211.5

25.737.529.3

55.722.821.3

23.73.99.7

23.57.6

17.9

25.210.724.2

23.69.4

21.8

53.79.2

20.6

54.017.941.4

54.726.360.9

54.528.965.5

74.54.7

11.3

74.68.4

20.3

74.512.329.7

74.916.841.0

86.91- 2.3-7.7

83.815.91- 0.9

91.4-3.419.6

77.00.51.3

81.513.7

7.6

85.11- 5.411.1

78.33.9

1- 6.7

11.27.55.9

47.732.935.4

62.516.518.8

23.5-0.89.1

23.3-1.117.7

25.9-0.723.9

23.5-0.820.7

58.7-0.420.7

58.9-1.140.4

59.2-2.459.7

59.0-1.268.1

79.80.4

11.0

79.8-0.223.2

79.9-0.433.0

80.1-2.382.9

83.11- 7.91- 1.6

79.323.71- 5.5

90.3-3.829.7

68.50.41.2

76.020.111.9

80.52- 2.115.6

71.35.2

2- 3.7

37.926.630.9

51.77.5

14.9

66.111.319.6

23.3-5.38.6

23.21- 0.516.7

26.11- 3.922.7

23.11- 1.918.9

43.2-7.613.9

43.41- 5.927.2

43.92- 4.740.9

43.72- 7.244.9

69.3-4.69.6

69.1-8.816.7

69.11- 2.624.8

69.12- 9.251.7

79.12- 3.21- 5.6

74.431.72- 0.1

89.4-3.838.5

60.90.01.1

70.826.515.1

75.62- 8.219.1

63.77.3

3- 0.5

47.540.057.7

43.520.840.7

57.021.235.9

13.9-8.92.2

13.91- 7.2

5.2

16.72- 2.9

6.7

13.71- 7.6

5.1

33.01- 3.0

4.5

33.22- 6.3

8.7

33.94- 0.714.4

33.75- 1.518.2

69.0-6.03.2

69.01- 1.4

4.7

69.01- 7.2

6.6

68.83- 7.412.4

75.12- 7.71- 9.3

69.339.72- 4.5

88.3-3.248.4

52.70.40.9

65.332.919.3

70.83- 3.922.7

56.29.7

3- 6.7

55.98.8

21.8

61.516.534.4

65.513.728.2

18.5-9.9-2.3

18.71- 9.1-3.4

20.62- 5.7-4.6

18.72- 2.9-4.3

37.71- 2.3-3.1

37.72- 4.1-4.3

38.73- 8.4-5.4

38.54- 9.2-8.4

69.3-6.1-0.8

69.01- 2.8-2.2

69.11- 8.7-4.0

68.93- 6.9-6.8

70.83- 2.02- 2.9

64.547.02- 8.2

87.1-2.357.4

44.5-0.10.8

60.238.723.7

65.63- 9.425.7

48.712.54- 2.9

64.49.8

28.7

63.510.642.5

71.814.687.3

18.5-6.4-6.5

18.61- 1.91- 3.0

20.11- 6.81- 8.9

18.61- 5.81- 7.5

37.9-7.7-8.8

37.71- 5.71- 7.8

38.92- 4.72- 6.9

39.23- 1.63- 6.0

69.0-4.8-5.8

69.0-8.51- 0.1

68.91- 3.11- 5.4

69.12- 3.22- 5.1

66.83- 5.52- 6.2

59.554.43- 1.7

86.0-1.166.4

37.20.20.4

55.244.527.7

60.94- 3.928.5

41.416.24- 8.4

69.54.0

35.9

62.20.8

12.6

67.0-5.042.7

23.30.7

1- 1.7

23.30.9

2- 3.7

23.22.5

3- 5.7

23.55.3

5- 0.9

43.20.4

-8.8

43.21.9

1- 9.2

43.22.2

2- 8.3

43.52.5

4- 6.4

69.31.0

-5.3

69.41.4

-9.8

69.51.4

1- 4.7

69.51.4

2- 5.5

62.43- 8.42- 9.2

54.960.93- 4.7

84.80.4

74.8

29.2-0.20.1

50.749.532.9

55.94- 8.231.2

33.920.25- 3.5

72.0-5.739.5

43.92- 2.635.5

65.02- 5.124.6

13.76.8

1- 3.2

13.613.32- 4.8

14.120.73- 8.4

13.936.06- 3.5

38.25.9

-9.9

38.211.31- 9.2

37.916.72- 9.2

37.529.35- 1.5

69.43.8

-5.3

69.46.3

-9.6

69.39.4

1- 4.9

69.515.02- 5.5

57.94- 0.53- 2.0

50.466.93- 7.2

83.42.5

83.5

21.7-0.3-0.2

46.254.238.5

50.55- 1.933.5

26.525.15- 8.2

66.62- 5.616.9

32.93- 6.529.8

15.01- 6.1

8.223.213.2-9.1

24.126.71- 7.5

24.239.22- 6.9

24.544.03- 0.7

43.212.3-7.7

43.524.21- 5.9

43.535.42- 3.3

44.763.24- 2.4

69.38.1

-5.0

69.514.5-8.7

69.320.91- 3.7

69.435.72- 4.7

53.24- 1.53- 4.7

45.772.33- 8.9

81.65.0

91.1

14.1-0.4-0.5

41.958.443.7

44.55- 4.534.5

19.630.96- 1.5

18.81- 2.2

4.9

13.31- 1.4-0.3

15.21- 0.8-9.3

18.912.6-2.4

18.925.6-3.4

21.934.5-4.8

18.728.7-4.1

38.516.3-3.0

39.531.8-3.8

39.948.0-5.1

38.967.5-9.0

69.49.3

-1.1

69.415.9-2.4

69.622.7-3.7

69.533.4-5.9

47.74- 0.23- 7.5

40.976.13- 9.9

79.48.4

97.8

6.9-0.4-0.7

37.461.048.9

37.95- 4.534.5

13.037.56- 3.5

6.2-1.3-2.8

6.93.3

-4.0

11.512.0-1.2

93.10.00.0

86.80.00.0

82.50.00.0

78.50.00.0

74.80.00.0

70.50.00.0

66.00.00.0

61.90.00.0

57.70.00.0

53.90.00.0

49.20.00.0

45.40.00.0

41.20.00.0

37.20.00.0

33.20.00.0

28.70.00.0

25.10.00.0

21.20.00.0

17.20.00.0

13.60.00.0

9.80.00.0

7.90.00.0

5.90.00.0

5.20.00.0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

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Coded by Lab numbers / Background L=50

7

8

45

0152255

0149255

0146255

0143255

0140255

0136255

0132255

0127255

0122255

0116255

0109255

51100255

9491255

12279255

14563255

16540255

1840255

35

0151255

0148255

0145255

0142255

0139255

0135255

0131255

0126255

0120255

0114255

45107255

8999255

11789255

14077255

16060255

17835255

1950255

25

0150255

0147255

0144255

0141255

0138255

0134255

0130255

0125255

0119255

34113255

83106255

11197255

13487255

15475255

17258255

18829255

2040255

9

0149239

0146239

0144239

0140239

0137239

0133240

0129240

0124240

16118240

75112240

105104240

12796241

14785241

16573241

18155241

19723242

2120242

00148221

0146221

0143221

0140222

0136222

0132222

0128222

0123222

66117222

97111223

120103223

14094223

15884223

17471223

19052224

20517224

2190224

03

0147203

0145204

0142204

0139204

0135204

0131204

0127204

54122205

88116205

112110205

132102205

15093205

16783206

18269206

19750206

2118207

2250207

96

0147186

0144186

0141186

0138186

0135187

0131187

36126187

77121187

103115187

124109188

142101188

15892188

17481188

18967189

20348189

2160190

2300190

98

0146169

0144169

0141169

0138169

0134169

0130169

64126170

93120170

114115170

133108170

150100171

16591171

18080171

19466172

20846172

2210173

2340173

80146151

0143151

0140152

0137152

0134152

47130152

80125153

104120153

123114153

140107153

156100154

17190154

18579155

19965155

21244155

2250156

2370156

84

0145134

0143134

0140134

0137135

15133135

65129135

92125136

112119136

130113136

146107137

16199137

17690137

18978138

20364138

21542139

2280139

2410140

76

0145117

0143117

0140117

0136117

45133118

77129118

100124119

119119119

136113119

151106120

16698120

18089121

19378121

20663122

21841122

2310123

2430124

7014599

0142100

0139100

0136100

59132101

86128101

106124101

124119102

140113102

155106103

16998104

18389104

19677105

20862105

22139106

2330107

2450108

7014581

014282

013982

3113683

6913283

9212884

11112384

12811885

14411285

15810586

1729887

1858887

1987788

2116189

2233890

235091

247092

7014462

014263

013963

4413664

7513265

9712865

11512366

13211867

14711268

16110569

1749769

1878870

2007671

2126173

2253774

237075

248076

7014440

014241

013942

5313543

8013244

10112845

11812346

13411847

14911249

16310550

1769751

1898753

2017654

2146055

2263657

238058

249060

601443

01426

21399

5813512

8313215

10312817

12012320

13611822

15011225

16410527

1779730

1908732

2027534

2156037

2273639

239041

250043

601440

01410

181380

621350

861320

1051270

1221230

1371180

1511120

1651050

178970

191870

203754

2156010

2273516

239020

251025

601440

01410

251380

641350

871310

1061270

1231230

1381170

1521110

1661050

179970

191870

204750

216600

228350

24000

25100

601440

01410

291380

661350

891310

1071270

1241230

1391170

1531110

1661050

179960

192870

204750

216590

228350

24000

25200

601440

01410

321380

671350

901310

1081270

1241230

1391170

1531110

1671040

180960

192870

205750

217590

229350

24000

25200

-100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90

-100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

90

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

90

100

a*

b*

L* = 50709 primariesWhite D65ReferenceD50Bradford yesGamma sRGBDot mark forout of gamutClipping forR-Y-G-C-B-M hexagonOuter blue areahuman gamut

-100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90

-100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 10 20 30 40 50 60 70 80 90 100

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

90

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

0

10

20

30

40

50

60

70

80

90

100

a*

b*

L* = 50709 primariesWhite D65ReferenceD50Bradford yesGamma sRGBDot mark forout of gamutClipping forR-Y-G-C-B-M hexagonOuter blue areahuman gamut

sRGB Numbers

8

9

5.1 CIELab / sRGB Grayscale Chart

Left 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.

Black Curve for gamma-encodedvalues C’=RGB’ for sRGB

Green Linear function, comparisonBlue Curve for values without gamma-

encoding C =RGBGray Density

Gamma encoded values are indicated byan apostroph only on this page

The Tone Reproduction Curve (TRC) fromL* to C’ is surprisingly nearly linear

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Bottom right:RGB graywedge, linear by numbers

0 0.0 1 3.6 2 7.3 3 10.9 4 14.1 5 16.8 6 19.3 7 21.5 8 23.5 9 25.5 10 27.5

10 27.5 11 29.5 12 31.5 13 33.5 14 35.6 15 37.7 16 39.8 17 41.9 18 44.0 19 46.1 20 48.3

20 48.3 21 50.5 22 52.7 23 54.9 24 57.1 25 59.3 26 61.5 27 63.8 28 66.1 29 68.3 30 70.6

30 70.6 31 72.9 32 75.3 33 77.6 34 79.9 35 82.3 36 84.7 37 87.0 38 89.4 39 91.8 40 94.2

40 94.2 41 96.7 42 99.1 43 101.5 44 104.0 45 106.5 46 108.9 47 111.4 48 113.9 49 116.4 50 118.9

50 118.9 51 121.4 52 124.0 53 126.5 54 129.1 55 131.6 56 134.2 57 136.8 58 139.4 59 142.0 60 144.6

60 144.6 61 147.2 62 149.8 63 152.4 64 155.1 65 157.7 66 160.4 67 163.0 68 165.7 69 168.4 70 171.1

70 171.1 71 173.8 72 176.5 73 179.2 74 181.9 75 184.6 76 187.3 77 190.1 78 192.8 79 195.6 80 198.3

80 198.3 81 201.1 82 203.9 83 206.7 84 209.5 85 212.3 86 215.1 87 217.9 88 220.7 89 223.5 90 226.3

90 226.3 91 229.2 92 232.0 93 234.9 94 237.7 95 240.6 96 243.5 97 246.3 98 249.2 99 252.1 100 255.0

L*0

RGB’

255

RGB

0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

Dens

0 20 40 60 80 100

10

0 0.3 1 4.0 2 7.6 3 11.3 4 14.4 5 17.2 6 19.6 7 21.8 8 23.8 9 25.8 10 27.8

10 27.8 11 29.8 12 31.8 13 33.9 14 35.9 15 38.0 16 40.1 17 42.2 18 44.3 19 46.5 20 48.6

20 48.6 21 50.8 22 53.0 23 55.2 24 57.4 25 59.6 26 61.9 27 64.1 28 66.4 29 68.7 30 71.0

30 71.0 31 73.3 32 75.6 33 77.9 34 80.3 35 82.6 36 85.0 37 87.4 38 89.8 39 92.2 40 94.6

40 94.6 41 97.0 42 99.4 43 101.9 44 104.3 45 106.8 46 109.3 47 111.7 48 114.2 49 116.7 50 119.2

50 119.2 51 121.8 52 124.3 53 126.8 54 129.4 55 132.0 56 134.5 57 137.1 58 139.7 59 142.3 60 144.9

60 144.9 61 147.5 62 150.1 63 152.7 64 155.4 65 158.0 66 160.7 67 163.3 68 166.0 69 168.7 70 171.4

70 171.4 71 174.1 72 176.8 73 179.5 74 182.2 75 184.9 76 187.7 77 190.4 78 193.1 79 195.9 80 198.7

80 198.7 81 201.4 82 204.2 83 207.0 84 209.8 85 212.6 86 215.4 87 218.2 88 221.0 89 223.8 90 226.7

90 226.7 91 229.5 92 232.3 93 235.2 94 238.1 95 240.9 96 243.8 97 246.7 98 249.6 99 252.4 100 255.3

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

5.2 CIELab / sRGB Rich Gray Chart

The gray chart on the previous page is printed either by K-only or by rich blackCMYK. Desktop printers print mostly by K-only.

The printer can be forced to print by rich black CMYK if the values RGB areslightly different. Here we have added 1 unit of 255 to the B channel. The gray isnot accurate, but good enough for a gray balance test.

11

5.3 K-only Gray Chart

0 1 2 3 4 5 6 7 8 9 10

10 11 12 13 14 15 16 17 18 19 20

20 21 22 23 24 25 26 27 28 29 30

30 31 32 33 34 35 36 37 38 39 40

40 41 42 43 44 45 46 47 48 49 50

50 51 52 53 54 55 56 57 58 59 60

60 61 62 63 64 65 66 67 68 69 70

70 71 72 73 74 75 76 77 78 79 80

80 81 82 83 84 85 86 87 88 89 90

90 91 92 93 94 95 96 97 98 99 100

0

10.0

20.0

30.0

40.0

50.0

60.0

70.0

80.0

90.0

A PostScript printer should print these charts by K-only. The patches can be usedto measure the dot gain.

12

6.1 Grayscale Conversions

A color images contains additionally a patch which is filled in Photoshop in sRGBmode by RGB=128/128/128. The image is then converted to grayscale by severaldifferent dot gains. The image does not change the appearance.If we choose in the color settings the same Gray Gamma 2.2 as a standard then thenewly loaded images will look different.The next page shows the converted images including the patch top right. The largenumber in the patch is the gray number after the conversion as measured by Photo-shop. R=G=B=128 is equivalent to L*=54 in the gray charts.

Grayscales by Photoshop should be saved by one of these formats- EPS without PostScript color management, with 8-bit TIFF preview- K-only CMYKTIFF can cause shifts by Export to PDF in PageMaker 6.52 and 7.01.Export to PDF by PageMaker 6.52 should be done in mode CMYK.This does not affect RGB images.Vector graphics should be defined by CMYK anyway.

For offset printing by K-only we have to use an appropriate dot gain, as recommendedby the service provider /printer. The images 7 and 8 (next page) show two versions,executed by modified profiles with Black Generation=Maximum (empty plates CMY)Color settings for Export to PDF:Settings File None / Leave Color Unchanged / Rendering Intent Default (or Rel.Col.).

The grayscale conversions work as follows:1. Remove gamma encoding for sRGB.

This is essentially a power function with gamma g1=2.2. The numbers are converted by c2= c1g1.

2. Apply dot gain encoding.Each dot gain has an equivalent gamma value g2 (simplified model). The numbers are converted by c3= c21/g2.

3. Altogether we get new numbers c3=c1g1/g2

For Gray Gamma=2.2 we get c3=c1.

Dot gain % Gamma R=G=B0 1.00 55

10 1.32 8015 1.51 9320 1.74 10525 2.00 118

28.2 2.20 12830 2.32 132

EC 104 Black Ink Euroscale Coated v2

13

1. Grayscale DG=10%

6.2 Grayscale Conversions / Saved as EPS

2. Grayscale DG=15% 3. Grayscale DG=20%

4. Grayscale DG=25% 5. Grayscale DG=30% 6. GrayscaleBlack Ink - Euroscale C. v2

80 93 105

118 132 104

7. Left: CMYK K-onlyBlack Ink - Euroscale Coated v2CMYK with three empty plates CMYCoded by four bytes per pixelExecuted by Eurostandard CoatedDot gain = 9%Black Generation=Maximum

8. Right: CMYK K-onlyBlack Ink - Euroscale Coated v2CMYK as aboveExecuted by Eurostandard CoatedDot gain = 15%Black Generation=Maximum(not available for Euroscale Coated)

The grayscales were saved as EPS. PageMaker’s Export to PDF in CMYK moderetains CMYK numbers and RGB numbers and gray numbers in grayscales.

14

6.3 Grayscale K-only Printing / PDF/X-1a

This chapter describes a workflow which is entirely based on one offset profile, herefor instance ISO Coated. The description follows Adobe CS2 with Acrobat7 Profes-sional.

Define color settings in Photoshop:RGB sRGB (for instance)CMYK ISO CoatedGray Black Ink ISO Coated (by loading ISO Coated)Spot Dot gain 20%Save as sRGB-ISO-ISO-20.csf

Synchronization by Bridge delivers in InDesign:RGB sRGBCMYK ISO CoatedGray Undefined (probably gamma=2.2)Spot Undefined

Manual synchronization for Acrobat delivers:RGB sRGBCMYK ISO CoatedGray Black Ink ISO CoatedSpot Undefined

Image processing by Photoshop:Color imageMode GrayscaleMake new doc in CMYK with white background and the same size by pixelsColor management: Use ISO Coated (the purpose is not clear, probably not wrong)Grayscale: select all, copyCMYK: paste into channel KSave CMYK as uncompressed TIFF, without embedding the ICC profile

Workflow in InDesign:Make documentPlace TIFFSave as PDF/X-1a, with modified joboptions:Downsample to 288dpi if above / use ZIP 8 bits per channel / Leave color unchangedUse Rendering Intent ISO Coated (this is merely an information)

Now we have a PDF/X-1a compliant PDF. Pure CMYK, but the channels CMY areempty, which should be told to the press people. The viewing conditions in Photoshop,InDesign and Acrobat are consistently defined by CMYK.An example for file size:Grayscale 458 kB, CMYK 1832 kB, ZIP8-PDF 519 kB. The compression ratio isn‘tgood for ZIP-8, but empty channels don‘t contribute much to file size.

15

7.1 Reflectance / Density / Visual Dot Area

The table on the next page shows the density D, the reflectance factor R, the CIE1931 luminance Y, the Lab lightness L* and the visual dot area A for different blackdensities Db.

All this is valid for assumed ideal conditions:

Density D Reflectance R CIE Y Lab L*Darkness infinite 0 0 0Paper white 0 1 100 100

In matrix calculations the range for Y is 0 to 1. Here we have, as in many programs,the range 0 to 100. Hence, Y is merely R multiplied by 100.

The visual dot area A is calculated by the Murray-Davies model.

Toner printers may have black at D=1.5.Offset and inkjet densities can be above D=2.

Calculation

D R

R

Y R

A

Y R if R

D

D

Db

= −

==

= −−

= >

−

−

−

log( )

10

100

1 10

1 10

011 3 ..

. /

*

008856

7 787 16 116

116 161

1

Y R else

L Y

= +

= −

Linearizattion for L*< 8

D

L R

L Y

>==

2 0528

903 29

9 03

.

* .

* .

16

Dens.D Refl.R CIE Y Lab L* Area A Area A Area A Area A Area A Area A Area A Area A0...2.8 0...1 0...100 0...100 Db=1.4 Db=1.6 Db=1.8 Db=2.0 Db=2.2 Db=2.4 Db=2.6 Db=2.82.8000 0.0015 0.15 1.43 1.00002.7500 0.0017 0.17 1.60 0.99982.7000 0.0020 0.20 1.80 0.99952.6500 0.0022 0.22 2.02 0.99932.6000 0.0025 0.25 2.26 1.0000 0.99902.5500 0.0028 0.28 2.54 0.9996 0.99872.5000 0.0031 0.31 2.85 0.9993 0.99842.4500 0.0035 0.35 3.20 0.9989 0.99802.4000 0.0039 0.39 3.59 1.0000 0.9985 0.99762.3500 0.0044 0.44 4.03 0.9995 0.9980 0.99712.3000 0.0050 0.50 4.52 0.9989 0.9974 0.99652.2500 0.0056 0.56 5.08 0.9983 0.9968 0.99592.2000 0.0063 0.63 5.70 1.0000 0.9976 0.9961 0.99522.1500 0.0070 0.70 6.39 0.9992 0.9968 0.9954 0.99442.1000 0.0079 0.79 7.17 0.9983 0.9960 0.9945 0.99362.0500 0.0089 0.89 8.05 0.9973 0.9950 0.9935 0.99262.0000 0.0100 1.00 8.99 1.0000 0.9962 0.9939 0.9924 0.99151.9500 0.0112 1.12 9.97 0.9987 0.9950 0.9927 0.9912 0.99031.9000 0.0125 1.25 10.98 0.9973 0.9936 0.9913 0.9898 0.98891.8500 0.0141 1.41 12.04 0.9958 0.9921 0.9898 0.9883 0.98741.8000 0.0158 1.58 13.13 1.0000 0.9940 0.9904 0.9880 0.9866 0.98571.7500 0.0177 1.77 14.27 0.9980 0.9921 0.9884 0.9861 0.9846 0.98371.7000 0.0199 1.99 15.46 0.9958 0.9899 0.9862 0.9839 0.9825 0.98161.6500 0.0223 2.23 16.69 0.9933 0.9874 0.9838 0.9815 0.9800 0.97911.6000 0.0251 2.51 17.97 1.0000 0.9905 0.9847 0.9810 0.9787 0.9773 0.97641.5500 0.0281 2.81 19.30 0.9968 0.9874 0.9816 0.9779 0.9757 0.9742 0.97331.5000 0.0316 3.16 20.68 0.9933 0.9839 0.9781 0.9745 0.9722 0.9708 0.96991.4500 0.0354 3.54 22.11 0.9893 0.9800 0.9742 0.9706 0.9683 0.9669 0.96601.4000 0.0398 3.98 23.60 1.0000 0.9849 0.9756 0.9698 0.9662 0.9640 0.9626 0.96171.3500 0.0446 4.46 25.15 0.9949 0.9799 0.9707 0.9649 0.9613 0.9591 0.9577 0.95681.3000 0.0501 5.01 26.76 0.9892 0.9743 0.9651 0.9594 0.9559 0.9536 0.9522 0.95131.2500 0.0562 5.62 28.44 0.9828 0.9680 0.9589 0.9532 0.9497 0.9475 0.9461 0.94521.2000 0.0631 6.31 30.18 0.9757 0.9610 0.9519 0.9463 0.9428 0.9406 0.9392 0.93831.1500 0.0708 7.08 31.98 0.9677 0.9531 0.9441 0.9385 0.9351 0.9329 0.9315 0.93061.1000 0.0794 7.94 33.86 0.9587 0.9442 0.9353 0.9298 0.9264 0.9242 0.9228 0.92201.0500 0.0891 8.91 35.81 0.9486 0.9343 0.9255 0.9200 0.9166 0.9145 0.9131 0.91231.0000 0.1000 10.00 37.84 0.9373 0.9231 0.9144 0.9090 0.9057 0.9035 0.9022 0.90140.9500 0.1122 11.22 39.94 0.9246 0.9106 0.9020 0.8967 0.8934 0.8913 0.8900 0.88920.9000 0.1259 12.59 42.13 0.9103 0.8966 0.8881 0.8829 0.8796 0.8776 0.8763 0.87540.8500 0.1412 14.12 44.41 0.8943 0.8808 0.8725 0.8674 0.8641 0.8621 0.8609 0.86010.8000 0.1584 15.84 46.77 0.8764 0.8631 0.8550 0.8500 0.8468 0.8448 0.8436 0.84280.7500 0.1778 17.78 49.23 0.8562 0.8433 0.8354 0.8304 0.8273 0.8254 0.8242 0.82340.7000 0.1995 19.95 51.78 0.8336 0.8211 0.8133 0.8085 0.8055 0.8036 0.8024 0.80170.6500 0.2238 22.38 54.43 0.8083 0.7961 0.7886 0.7839 0.7810 0.7792 0.7780 0.77730.6000 0.2511 25.11 57.19 0.7798 0.7681 0.7608 0.7563 0.7535 0.7518 0.7506 0.75000.5500 0.2818 28.18 60.05 0.7479 0.7366 0.7297 0.7254 0.7227 0.7210 0.7199 0.71930.5000 0.3162 31.62 63.03 0.7121 0.7013 0.6947 0.6906 0.6881 0.6865 0.6854 0.68480.4500 0.3548 35.48 66.12 0.6719 0.6618 0.6555 0.6517 0.6492 0.6477 0.6468 0.64620.4000 0.3981 39.81 69.33 0.6268 0.6174 0.6115 0.6079 0.6057 0.6043 0.6034 0.60280.3500 0.4466 44.66 72.67 0.5762 0.5675 0.5622 0.5589 0.5568 0.5555 0.5547 0.55410.3000 0.5011 50.11 76.14 0.5194 0.5116 0.5068 0.5038 0.5019 0.5008 0.5000 0.49960.2500 0.5623 56.23 79.74 0.4558 0.4489 0.4447 0.4420 0.4404 0.4394 0.4387 0.43830.2000 0.6309 63.09 83.49 0.3843 0.3785 0.3749 0.3727 0.3713 0.3705 0.3699 0.36960.1500 0.7079 70.79 87.38 0.3041 0.2995 0.2967 0.2950 0.2939 0.2932 0.2927 0.29250.1000 0.7943 79.43 91.43 0.2142 0.2109 0.2089 0.2077 0.2069 0.2064 0.2061 0.20600.0500 0.8912 89.12 95.63 0.1132 0.1115 0.1105 0.1098 0.1094 0.1091 0.1090 0.10890.0000 1.0000100.00 100.00 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

7.2 Reflectance ... / Table

17

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0CMYK Input

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

CM

YK

Prin

ted

1.02.03.0

1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0G0

5

10

15

20

25

30

35

40

45

50

%

dgG dg

1.00 0.01.10 3.31.20 6.51.30 9.41.40 12.11.50 14.61.60 17.01.70 19.21.80 21.31.90 23.22.00 25.02.10 26.72.20 28.22.30 29.72.40 31.12.50 32.32.60 33.52.70 34.62.80 35.62.90 36.63.00 37.5

G dg

1.00 0.01.07 2.51.15 5.01.23 7.51.32 10.01.42 12.51.51 15.01.62 17.51.74 20.01.86 22.52.00 25.02.15 27.52.32 30.02.51 32.52.74 35.03.00 37.5

8.1 Dot Gain

This diagram shows the growthof the area of printed dots on thepaper.A printer tone reproduction curveis often similar to a power func-tion, like the so-called Gammafunction for a monitor, but shownsomewhat mirrored.For Gamma=2.0 we read for theinput 0.50 (50%) the output value0.75 which is interpreted as dotgain 25%.According to ISO the dot gain hasto be measured at 40%.Photoshop seems to use 50%.

A gray profile can be derived from a color CMYK profile. But it seems that the dotgain is different for rich black and K-only.

x

y

Formulas

y x

y x

At x

dg y x x

dg x

G

G

o

o o

oG

( ) ( )

( )

( )

( )

1 1

1 1

1 1

− = −

= − −

= −

= − − − xx

For x

left diagram table

dg

For x

dg

o

o

G

o

=+

= −

=

= −

0 5

0 5 0 5

0 4

0 6

.

( )

. .

.

. 00 6

100

.

%

G

Multiply dg by

The lower diagram shows the dotgain as a function of Gamma.

18

8.2 Dot Gain

This diagram shows the den-sity D and the value K as func-tions of the CIELab lightness.

The function K(L*) is based onmeasurements L* in a swatchbook for Euroscale Coated v2.A simple quadratic functionwas used for curve fitting.

L* = 0 means darknessL* = 100 means paper white

L*0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

D

0

10

20

30

40

50

60

70

80

90

100

K

0 20 40 60 80 100

L L

K L L

=

= − −

* /

( . . . )

100

100 1 125 0 5 0 625 2

19

9. Black Generation

Black Generation means the strategy howto replace CMY ink by K ink in dark areas.UCR (Undercolor Removal):Equal amounts of color ink are replacedby K ink in neutral areas.GCR (Gray Component Replacement):Equal amounts of color ink above a certainlevel are replaced by K ink everywhere.

The curves were created by Gretag Mac-beth Profile Editor, mode Graybalance:’The Gray Balance window indicates thecurve of the Lab lightness axis for eachcolor channel. The L* range (= Lightnessaxis) is from 0 to 100.’

This cannot be true. At least are the axesin reverse direction.

Euroscale Coated v2 uses medium GCR,ISO Coated heavy GCR and the inkjet wasprofiled for light GCR. This is necessary inorder to avoid the so-called pepper effect.Stronger GCR stabilizes the graybalance.

Characterizations like medium, heavy orlight are not standardized.

Offset Profile ISO Coated

Inkjet Profile for Mutoh 6100

Offset Profile Euroscale Coated

20

10. Files

This document is available in two versions:

Web Preview / about 300 kB

http://www.fho-emden.de/~hoffmann/a3gencolortest.pdf

High Quality JPEG / ZIP 144dpi / about 2 MB

http://www.fho-emden.de/~hoffmann/a3gencolorhigh.pdf

EPS file for the IT8 target 50 kB

http://www.fho-emden.de/~hoffmann/targetrgb.txt

Please rename to targetrgb.eps

The file contains a reference data table

View and print by Photoshop, PageMaker or InDesign

This document was tested by

QMS 6100 Magicolor

Fargo Pictura 310e

Lexmark 4079 plus

Mutoh RJ 6100 + PosterShop Pro

Mutoh RJ 6100 + Best Colorproof

Mutoh RJ 6100 + ColorGate ProductionServer

Okidata C9600

Gernot HoffmannJanuary 26 / 2008

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