Re: ECI-EN digest, Vol 1 #96 - 5 msgs - ECI-EN

5 Aug 2004

      The overriding reason  for RGB equal value producung neutral and CMYK needing different
values for cyan and the magenta - yellow is the colour or
spectral response of the ink set.

Yellow is the best ink but cyan and magenta have large transmission errors.  Magenta is
contaminated with yellow and a little cyan - cyan ink is
contaminated with magenta and yellow.

To produce a neutral in CMYKthe grey balance must be altered to remove the imbalance
caused by the contaminants.  The balack also helps to build up
density lost by balancing the ink set to make neutrals.

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 Today's Topics:

   1. Re: RGB to CMYK  with ISO web coated profile (Andy Psarianos)
   2. Re: RGB to CMYK  with ISO web coated profile (Chris Murphy)
   3. Re: RGB to CMYK  with ISO web coated profile (Peter Kleinheider)
   4. Re: RGB to CMYK  with ISO web coated profile (Paul Sherfield)
   5. Re: RGB to CMYK  with ISO web coated profile (Peter Kleinheider)

 --__--__--

 Message: 1
 From: Andy Psarianos &lt;andy(a)psarianos.com&gt;
 Subject: Re: [ECI-EN] RGB to CMYK  with ISO web coated profile
 Date: Tue, 3 Aug 2004 21:46:12 +0100
 To: eci-en(a)lists.transmedia.de
 Reply-To: eci-en(a)lists.transmedia.de

 Paul,

 Thanks that's really helpful.

 Yes indeed I am talking about the latest release of the profile called
 "ISO web coated"

 For example if I convert the following values I get the following
 results.

  From RGB Adobe 1998:

 RGB 50,50,50 to "SWOP" CMYK = 70,64,63,62
 (C highest and M and Y are similar values)

 RGB 50,50,50 to "ISO web coated" CMYK = 64,53,48,71
 (C highest M in middle and Y lowest)

 I'm not saying SWOP is correct, but if I were to remove the black
 separation it would appear grey wouldn't it? I don't believe the values
 in the ISO web coated values would be neutral. If this is the case, the
 question is why?

 I do understand that the lack of yellow in the dark greys could be
 hidden by the heavy black, but I don't understand why this was done,
 and why a more "conventional & balanced grey" was not chosen. Is it
 simply that when printing shadows with equal amounts of m and y they
 have a "yellowish hue" or is this an ink trapping issue?

 Overall, all tests I've done with the ISO web coated profile in
 conversions results have been very good. I'm willing to accept that
 these "unconventional values" in principle are OK, although I have
 several sceptics here which I need to convince.

 I would like to know what the reason was for this choice, if indeed it
 was a choice.

 Can anyone help shine some light on this decision?

 many thanks

 Andy Psarianos

 On 30 Jul 2004, at 18:38, Paul Sherfield wrote:

  Hi Andy

 Yes it does look a little odd, but works well in practise, due to the
 GCR
 setting I think. This is the latest ISO wed coated icc, as of a few
 months
 ago?

 Worked very well for me when a client was given Euroscale coated v2 for
 sheetfed images for a wed offset production with lots of neutral
 consumer
 electrical images. I was called in after the first printing!! We
 changed the
 Euroscale coated v2 to ISO web coated with good results when reprinted.

 Regards

 Paul Sherfield

 The Missing Horse Consultancy Ltd

 Telephone: 01442 871752
 Mobile: 07899 906385

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 --__--__--

 Message: 2
 Cc: Andy Psarianos &lt;andy(a)psarianos.com&gt;
 From: Chris Murphy &lt;lists(a)colorremedies.com&gt;
 Subject: Re: [ECI-EN] RGB to CMYK  with ISO web coated profile
 Date: Tue, 3 Aug 2004 15:03:16 -0600
 To: eci-en(a)lists.transmedia.de
 Reply-To: eci-en(a)lists.transmedia.de

 On Aug 3, 2004, at 2:46 PM, Andy Psarianos wrote:
  RGB Adobe 1998:

 RGB 50,50,50 to "SWOP" CMYK = 70,64,63,62
 (C highest and M and Y are similar values)

 RGB 50,50,50 to "ISO web coated" CMYK = 64,53,48,71
 (C highest M in middle and Y lowest)

 I'm not saying SWOP is correct, but if I were to remove the black
 separation it would appear grey wouldn't it? I don't believe the
 values in the ISO web coated values would be neutral. If this is the
 case, the question is why?

 I do understand that the lack of yellow in the dark greys could be
 hidden by the heavy black, but I don't understand why this was done,
 and why a more "conventional & balanced grey" was not chosen. Is it
 simply that when printing shadows with equal amounts of m and y they
 have a "yellowish hue" or is this an ink trapping issue? 
 I see this frequently with inkjet printing. If the yellow ink is very
 saturated (pure) compared to the other inks, it will take less yellow
 to balance the blue produced by cyan and magenta. And some yellow inks
 can be fairly green, which would take more magenta to further offset
 that contamination in the yellow.

 Off hand I can't say what yellow ink hue is being used with ISO web
 coated, but this is probably what's going on. This is why color by the
 numbers doesn't work unless you know the inkset and the print behavior
 of the press/printer very well. CMYK numbers are ambiguous.

 Chris Murphy
 Color Remedies (TM)
 www.colorremedies.com/realworldcolor
 ---------------------------------------------------------
 Co-author "Real World Color Management"
 Published by PeachPit Press (ISBN 0-201-77340-6)

 --__--__--

 Message: 3
 Date: Wed, 04 Aug 2004 10:49:03 +0200
 From: Peter Kleinheider &lt;pkleinheider(a)a1.net&gt;
 Subject: Re: [ECI-EN] RGB to CMYK  with ISO web coated profile
 To: eci-en(a)lists.transmedia.de
 &lt;282E5EE1-E58E-11D8-A683-000393468A5E(a)psarianos.com&gt;
 Reply-To: eci-en(a)lists.transmedia.de

 Andy

 When you do a relativ Colormetric Conversion from AdobeRGB to ISO Web
 Coated, a different way of gray-generation gets used as of perceptual.

 Since in a print run the yellow color is (usually) the last coler,
 Heidelberg (Profiles are done with Heidelberg PrintOpen) found that the
 yellow color is often reflecting and the color gets lighter the more
 yellow is on the sheet in a darkgray area. Therefor in the RelCol RI,
 the yellow color gets reduced a little bit more. Even at about 85%
 Gray, the values of yellow stall or drop when the color gets darker.

 When you separate using the Perceptive RI, you will find CMYK-Values
 that you would more consider as to be gray. But in real world pint
 production, you will not see much difference.

 Maybe Mr. Bestmann from Heidelberg cann explain that better.

 rgds

 Peter Kleinheider

 Am 03.08.2004 um 22:46 schrieb Andy Psarianos:

  Paul,

 Thanks that's really helpful.

 Yes indeed I am talking about the latest release of the profile called
 "ISO web coated"

 For example if I convert the following values I get the following
 results.

 From RGB Adobe 1998:

 RGB 50,50,50 to "SWOP" CMYK = 70,64,63,62
 (C highest and M and Y are similar values)

 RGB 50,50,50 to "ISO web coated" CMYK = 64,53,48,71
 (C highest M in middle and Y lowest)

 I'm not saying SWOP is correct, but if I were to remove the black
 separation it would appear grey wouldn't it? I don't believe the
 values in the ISO web coated values would be neutral. If this is the
 case, the question is why?

 I do understand that the lack of yellow in the dark greys could be
 hidden by the heavy black, but I don't understand why this was done,
 and why a more "conventional & balanced grey" was not chosen. Is it
 simply that when printing shadows with equal amounts of m and y they
 have a "yellowish hue" or is this an ink trapping issue?

 Overall, all tests I've done with the ISO web coated profile in
 conversions results have been very good. I'm willing to accept that
 these "unconventional values" in principle are OK, although I have
 several sceptics here which I need to convince.

 I would like to know what the reason was for this choice, if indeed it
 was a choice.

 Can anyone help shine some light on this decision?

 many thanks

 Andy Psarianos

 --__--__--

 Message: 4
 Date: Wed, 04 Aug 2004 09:55:26 +0100
 Subject: Re: [ECI-EN] RGB to CMYK  with ISO web coated profile
 From: Paul Sherfield &lt;paul(a)missinghorsecons.co.uk&gt;
 To: &lt;eci-en(a)lists.transmedia.de&gt;
 CC: Andy Psarianos &lt;andy(a)psarianos.com&gt;
 Reply-To: eci-en(a)lists.transmedia.de

 Hi Andy

 It does look odd, but as Chris Murphy said the yellow can do strange things
 within a CMYK grey balance.

 I believe this GCR setting within the profile is causing the results you are
 seeing, reducing the yellow in a RGB to CMYK conversion to reduce the
 possibility of a yellow bias.

 The grey balance for ISO for the CMY is:

                            Cyan      Magenta      Yellow
 Quarter tone          25%       19%           19%

 Mid tone                50%       40%           40%

 Three qu. tone       75%       46%           46%

 But this will not reflect the profile and any GCR that would be applied with
 a RGB to CMYK conversion.

 As you say the ISO profiles do work well, if the printers follow the
 standard printing conditions associated with each profile.

 Regards

 Paul

 The Missing Horse Consultancy Ltd

 Telephone: 01442 871752
 Mobile: 07899 906385

 --__--__--

 Message: 5
 Date: Wed, 04 Aug 2004 11:04:13 +0200
 From: Peter Kleinheider &lt;pkleinheider(a)a1.net&gt;
 Subject: Re: [ECI-EN] RGB to CMYK  with ISO web coated profile
 To: eci-en(a)lists.transmedia.de
 Reply-To: eci-en(a)lists.transmedia.de

 Paul

 This is just a recomendation and does not take in concern any color
 cast of the paper.

 the issue is: if a printer is printing according to ISO 12647, then the
 colors will turn out to be gray on the prints (when doing a separation
 of AdobeRGB or ECI-RGB to ISO Web coated)

 Am 04.08.2004 um 10:55 schrieb Paul Sherfield:

  The grey balance for ISO for the CMY is:

                            Cyan      Magenta      Yellow
 Quarter tone          25%       19%           19%

 Mid tone                50%       40%           40%

 Three qu. tone       75%       46%           46% 
 Peter

 --__--__--

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John C. Hamilton
Input Technology Specialist
PMP Digital Melbourne
359 Plummer Street
Port Melbourne 3207
Victoria Australia
Ph  61 3 9245 1222
Fax 61 3 9646 6887
Email john.hamilton(a)pmpdigital.com.au

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