Source Profile's relationship to Output Profile

Discuss QuarkXPress color management functionality including DeviceN workflows

Source Profile's relationship to Output Profile

Postby Glenn McDowall » 06 Jan 2012, 02:06

[b]Background:
Because the Quark Color Manager is always on in QuarkXPress 7 and 8, color information from older projects may display and/or print differently than they did in QuarkXPress 6.5. By default QuarkXPress 7 and 8 both use an internal LAB color space to describe color information. While the LAB color space provides one of the widest possible color spaces used to describe color, it can also cause color transformations to take place when older QuarkXPress files are opened in version 7 and 8. This may especially be true for images imported into a QuarkXPress layout. By default, QuarkXPress does not convert images of the same color space on output unless you explicitly set this control (For example, turning on[b]Color Manage CMYK Sources to CMYK Destinationsin the[b]Source Setupdialog)..

The color transformation occurs because QuarkXPress 6.5 and earlier used an internal CMYK/RGB color engine to describe color (assuming that QuarkCMS was turned off when the project was originally created). You can minimize this color transformation by selecting[b]QuarkXPress Emulate Legacyin the[b]Color Manager Preferencespane. However, you may still see color mismatches for both process and spot color information, especially for any Pantone colors that are used in the legacy project. This is due to changes that have been made in the color look-up tables provided in the latest Pantone Color Libraries. Ultimately, there is no one 'switch' you can turn on or off to get color information to perfectly match what you saw in earlier versions of QuarkXPress. Color matching, being as much an art as a science, involves applying the right incoming source profiles, the correct transformation engine (Kodak, ColorSync, or LogoSync, for example), and the right output profiles for the output devices you use in your unique production workflow.
Article IDAE0351


The above is quoted from one of your Knowledge base articles
I'm trying to understand where colour transforms are potentially happening .

the bit in this Knowledge base articles that says
By default, QuarkXPress does not convert images of the same color space on output unless you explicitly set this control (For example, turning on[b]Color Manage CMYK Sources to CMYK Destinationsin the[b]Source Setupdialog)..
- Does this mean that by turning on this option in the Source Setup that when the Output Setup's profile is different you'll get profile to profile conversion on all cmyk?What happens in a scenario where cmyk Source profile, placed image profile, and Output profile are all different?
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Postby Graham PM (Quark) » 11 Jan 2012, 15:23

This could turn into a very complicated discussion very quickly :). This is a very simplified version of how it works, from version 7.0 to the present,: when you import a raster image, it has a colour space. It could have an embedded profile, in which case its colour space is ICCProfile space; otherwise it is in a Device Space -- that is, the values in the raster are taken unadulterated as the values in the output device. Except for the case of 'AsIs' the output device has a single profile. In the case of the screen, it is the monitor RGB profile, in the case of a printing device it will usually be some CMYK profile. In the case of images without a profile, some conversion usually has to take place... the screen is RGB, the output device is usually some other space, so if your image is CMYK, it has to get converted at least once, to screen RGB, and most likely once again for the output context if its colorspace does not match. For images with embedded profiles, there is nearly always going to be conversion taking place UNLESS the output device has the same profile. A colour conversion from A to B is a two step affair: it involves an intermediate guy C. C is a mathematical colorspace that can hold a very large gamut of colours, much larger than any one real colour space can hold. It's like having an uber language called Bob. If your main language is French, all you need to know is how to translate French to Bob and Bob to French. Likewise for English, German, Urdu, etc. Now if you want to translate French to Urdu, it is done in two steps French->Bob->Urdu. And so on.So the first step is to convert A into the magic colorspace C. The next step is to convert C to B. Assuming that previews are always going converted, you can prevent XPress conversion of your image at output, either by choosing the AsIs set up, which will export your image in the colorspace it came in, or by ensuring that the profile of the output device matches the profile of your image. In the normal case, XPress uses one profile for the output device and everything is converted to that before output: if it is going to PostScript, for instance, CMYK will output to /DeviceCMYK space. If you allow colour management in output, then the profiles for individual images are transferred to the output device: in that scenario, if your image has a profile your image pixel data will not be converted by XPress (it *will* be converted by the RIP later on though). So, I think you can see the answer now to your question. What happens in a scenario where cmyk Source profile, placed image profile, and Output profile are all different, is that conversion happens at each point where a difference occurs.
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Postby Glenn McDowall » 13 Jan 2012, 04:29

Hello Graham, Thanks for your reply, I'm quite happy for it to get a bit more complicated, maybe not too much :)
I'm also struggling to ask the right questions so that its clear in my head. It's quite a different approach to Adobe.


Q1: Is Quark's[b]Source Setupthe same as InDesign's Working Spaces? Objects created in quark and items without a profile take this as their "Default" space?
Q2: Are the following statements correct?Turning on[b]Color Manage CMYK Sources to CMYK Destinationsin the[b]Source Setup This is NOT the same as asking InDesign to Convert to Working Space NOR is it the same as asking InDesign to Assign Profiles This IS a flag to allow Quark to convert from one cmyk color space (which may be a "Preserved" ICC attached to a placed file, or, the "Default" (from the Sources Setup)) to a second cmyk color space (as Defined by the[b]Output Setupin the case of a cmyk). IF the[b]Output Setupwas[b]As Isthen, EVEN if[b]Color Manage CMYK Sources to CMYK Destinationsis switched[b]on,No conversion would take place, only the cmyk numbers would be sent (DeviceCMYK).IF theOutput SetupwasAs Iswith Use Device Independent Colour checkedthen, EVEN ifColor Manage CMYK Sources to CMYK Destinationsis switchedon,No conversion would take place, The cmyk numbers would be sent along with an ICC profile based on the the Preserved.IF theOutput SetupwasComposite CMYKthen, ifColor Manage CMYK Sources to CMYK Destinationsis switchedon,everythingis converted profile to profile toDeviceCMYKexceptanything that has the exact same profile as the one in theOutput Setup.Q3: Is the following correct? Quark 7 8 & 9 use Lab internally to color manage so in order to get to screen rgb it has to convert everything to Lab then convert to screen rgb, this includes all placed rgb, so unlessColor Manage RGB Sources to RGB Destinationsin theSource Setupis switched on, the on-screen appearance could be wrong.Q4: In Quark's Preferences > Application > Display > Monitor Profle: Automatic what is used by Default?Q5: In Quark's Preferences > Application > Display > Monitor Profle: should this actually be set to your unique monitor profile?Q6: What is the purpose of this Preference does Quark use this separately to the OS?Q7: Many people confuse Postscript Color Management with the ICCProfile when saving a Photoshop EPS. Which file Formats is Quark able to read the ICC Profile and handle conversion to output?p.s. Matthias' tip of turning on the Develop Menu in Safari then selecting a Firefox as a User agent allows me to get the Returns. but cutting and pasting from Mail seems to really mess some other stuff like font heights[:(]
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Postby Graham PM (Quark) » 04 Feb 2012, 11:49

Sorry, Have only just spotted your reply. Not sure why I don't get pinged anymore when threads get added to.
I don't have answers to many of your questions. Especially the InDesign onces because I haven't actually used or looked at it for many years.
I can do the easy ones.
Q3 XPress uses various colour management agents, e.g. Colorsync, Logosync and Kodak. They all do the same thing. Convert colours to a central space, usually XYZ (can be LAB), and then convert from there to the destination space, e.g. a monitor or an output print context.
Q4 I think the default monitor profile is going to be whatever the OS tells QXP is the current profile to be used for the monitor. If you are running two or more monitors that require separate profiles I don't think QXP solves that problem... it will use the default monitor profile for all monitors: on a Mac that is going to be the main monitor (one with the menu bar).
Q7 QXP will try to read embedded profiles from all source images that support them. Even GIF files, which are only ever indexed colour, can have ICCProfiles embedded. As I recall, the only file formats that don't have embedded profiles are BMPs, Scitex CTs and PC WMFs.
Generally, the current shipping versions of XPress will convert all images to the target profile space that you have configured for output, and write them out as /Device spaces in PostScript. QXP can write out to /CIEABC space, but you have to create a new AsIs colour output set up, check the box for colour management, and select that one in the options->Color tab when the dialog fires up at the start of printing. It wll also write out the mechanics of a particular profile out as PostScript, for those people who don't trust their RIPs ability to manage the /CIEABC space. That does come with a gotcha though. Files get big, and the interpolation used is not always going to be optimal.
For your other Qs, I will have to ask someone else what is intended.
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Postby Glenn McDowall » 05 Feb 2012, 23:50

Hi Graham, again many thanks for your answers.
If you can get someone to check my logic for Q1 and Q2 that would be great.

From a different thread re photoshop postscript color mangement:
Graham PM (Quark) wrote:You can also get half the way there by converting to an XYZ space using the /CIEABC mechanism available from level2 PostScript onwards.

I was under the impression that if you take the half way there approach (checking postscript color management in the second dialogue box of Save As EPS from photoshop) that Quark 8 onwards could not convert this to a different space. So for example saving an RGB image with p-c-m, quark is unable to convert to cmyk. Your answers in this thread imply I'm completely wrong on this since Quark is internally using XYZwhy would it be unable to convert to DeviceCMYK?
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Postby Graham PM (Quark) » 06 Feb 2012, 19:25

PostScript doesn't have support for ICCProfiles, so there are basically 4 options. I am assuming that you are quite interested in the options that avoid data conversion...
[a] Convert the image to a /Device space. e.g. /DeviceCMYK.
This says, I know the profile of my output device. The channel data for my image is already in that space. Do no further conversions.
If you save out your Photoshop EPS without colour management, this is probably what you get. This is also the default behaviour for QXP.
[b] Convert the image to a large gamut space, e.g. XYZ or Lab space, and write out to PostScript as /CIEABC.
This says, I do not know the profile of my output device. My printer will take care of that later. However, I [b]do know how to convert my image to a wide gamut with hi fidelity interpolation, so that you have the best chance of converting my channels to the output device set up.
[c] Send the channel data untouched, but supply the embedded ICCProfile as a huge lump of PostScript procedures and tables.
This is what happens when you check that colour management box when you save out your Photoshop document to EPS.
Authoring programs do this to answer a customer demand: customers want colour management but don't want channel data changed.
Of course, this means passing the buck to PostScript. My money would be on Photoshop to do a better job than PostScript.
Channel data will, of course be changed further downstream, but not by the authoring program. This method works OK for Photoshop because it only has the one image to worry about for a layout product like QXP, which may be asked to create PostScript output with hundreds of images, converting the ICCProfiles like this could result in a major RIP-clogging event. There is also the problem that to avoid huge datasets the tables in an ICCProfile are quantized and have to be interpolated: the quality of that interpolation is likely going to be a lot better coming from a CMM rather than a PostScript executable.
[d] Says, if the source is already in the colorspace of the output device (e.g. CMYK), then do NOT convert the data: pass it on as /DeviceCMYK.
Your success with [d] depends on whether or not the source data comes with a profile.
If the image did not originally have an embedded profile, then this is probably your only option anyway, since there is no hint at how the CMYK data was derived. However, ignoring the embedded profile is unlikely to get you the best results because the source data and the embedded profile are linked together.QXP offers this option, but this must be used with great care.it is sort of like taking the RAW data from a Nikon and pretending it was the RAW data from a Canon.
QXP offers all these alternatives if it can get to the source data. In the case of EPS files, its predominant policy is to pass through the PostScript to output unadulterated. Probably the big case where that is not true is if you have some transparency that requires flattening.I am not sure what happens if an EPS contains something like an RGB and the output color setup is for CMYK. In those scenarios it could be that QXP uses JAWS to convert to those images to the output colour space. Will have to check.
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Postby Glenn McDowall » 08 Feb 2012, 23:59

Wow so much good data Thanks again.
At the risk of making my head hurt, can I ask some supplementary questions?


[B]Convert the image to a large gamut space, e.g. XYZ or Lab space, and write out to PostScript as /CIEABC.
This happens when you use an Output Setup [b]As Is with Use Device Independent Colour checked?
At first this seems to offer an Expert level workflow particularly suited to profiled RGB, is 16bit supported?
If the placed image is profiled CMYK does the CIEABC give a route back to the same black generation as was in the original or is it lost?


[C] Send the channel data untouched, but supply the embedded ICCProfile as a huge lump of PostScript procedures and tables.
This happens when a certain Photoshop EPS is passed unadulterated into the postscript. Or does Quark add this into [B] too?
Really it seems no-one wants this anymore Quark, Adobe, Pre-Press, and RIP are all spluttering and passing the buck. The only people using it are ignorant of its function! (or are CM genius with really old postscript RIPs[+o(])


[A]Convert the image to a /Device space. e.g. /DeviceCMYK.

This says, I know the profile of my output device. (is there an IF missing here) The channel data for my image is already in that space. Do no further conversions.

.....This is also the default behaviour for QXP.

[D]Says, if the source is already in the colorspace of the output device (e.g. CMYK), then do NOT convert the data: pass it on as /DeviceCMYK.


[A]Convert Happens when you choose an output space that is [b]NOT As Is. So CMYK or CMYK+Spot or RGB. [b]AND subject to Quark's Source settings about handling for example [b]Color Manage CMYK Sources to CMYK Destinations must be checked before .

[D](e.g. CMYK), then do NOT convert the data: pass it on as /DeviceCMYK.
[b]IF the source is already in the colorspace of the output device
[b]OR As Is is chosen in the Output Space (assuming Use Device Independant colour is unchecked , so not [B] )
[b]OR IF Quark's Source settings about handling for example [b]Color Manage CMYK Sources to CMYK Destinations is unchecked.
[b]OR IF Quark's ColourManager Prefs settings have [b]Color Manage Vector EPS/PDF is unchecked, then EPS and PDF are passed on as /DeviceCMYK.

This brings me back to my original question, how does Quark's Source Setup (rather than the image's source) influence this decision?
If an image has No profile attached does Quark Assign it the one in Quark's Source Setup so that it Converts [A] on output ,or temporarily assign it the same as the Output Setup so that its gets passed through as /DeviceCMYK[D]? I can see benefits of doing either.
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Postby Graham PM (Quark) » 09 Feb 2012, 19:00

R&D is immersed on future beasts, so the versions that you work with can be completely different animals from the stuff I work with every day. I will have to do some more research on what the shipping QXP does. That sounds bizarre, I know.
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Postby Head » 07 Jun 2012, 13:41

Hello Graham, Glenn (or anybody else that knows!),
We've seen a noticeable shiftin the colours of our four-colour litho printed work sent to CTP from PDF filescreated by QXP 8 compared with the results we used to get from QXP 6. What I'mreading above causes some concern regarding how colour values travel throughQXP.
I believe QXP's colour management continues to remain a minefield on which manyfolk could still use some SIMPLE clarification. Please could I therefore chipinto this ageing discussion with a few greatly simplified questions, based onan equally simplified example scenario, as follows:
[b]
The scenario
I have two CMYK images saved from Photoshop, one with, and one without, anembedded profile.
Both images were converted from RGB to CMYK in Photoshop using a colour profilerepresentative of our commercial printer's litho press.
I want to place both images into my QXP 8 or 9 layout (which uses only CMYK colours)and subsequently create a PDF file to send to our commercial printer for lithoprinting.
I want QXP to render the layout on my calibrated display as accurately aspossible (i.e. so that it matches the anticipated printed result as closely aspossible).
[b]But most importantly, I want the CMYKcolour numbers in the imported images (and of course elsewhere in mylayout) to remain absolutely unchanged throughout the layout > PDFprocess, e.g. so that the CMYK colour values of the images in the resultant PDFfile remain the same as they were in Photoshop when the original images werecreated.
[b]

Questions
The overarching question
How can I ensure all CMYK colour numbers remain unaltered by QXP throughout thelayout > PDF process, whilst at the same time achieving colour accuracy onmy calibrated display? I'd say this is what most users want to be surethey achieve.

Re: Color Setups > Source Setup

1. Is it correct to assume that the onlytwo purposes of the Source Setup are to:
a) provide a colour space reference to assistwith on-screen soft proofing, subject to the Output Setup' selected in View> Proof Output'; and
b) to provide a default colourspace reference that is used when an imported image does not have an embeddedprofile, so that appropriate colour value conversions CAN be achieved if the Colormanage sources to destinations' check boxes are switched ON in the SourceSetup, or if an RGB or spot colour image is encountered in a layout which isbeing output as CMYK?

2. Assuming the the Color manage sources to destinations'check boxes are all OFF, is it correct to assume that the other choicesselected in Source Setup will NEVER, EVER result in a change to the CMYK colournumbers at the PDF output stage?

3. What should form the basis of an informed decision whetherto use one of QXP's supplied Source Setups (i.e. based on Quark's Generic' orLegacy' colour space profiles) or alternatively create one's own, for examplebased on the CMYK profile of a commercial printer's litho press; and will theresults of these choices be manifested in any way other than soft proofing onscreen, or when colour conversions are required (e.g. from RGB or spot to CMYK,or if the Color manage sources to destinations' options are checked on)?

4. If I set up my own Source Setup using a CMYK profile that isdifferent to the CMYK profile embedded in one of the four-colour imagesimported into my layout, will QXP convert the colour numbers in that image evenif the Colour manage sources to destinations' check boxes are all OFF in theSource Setup?

Re: Color Setups > Output Setup
1. When exporting the layout to PDF (or PostScript), arethere any circumstances at all under which the colour numbers of the importedCMYK images will be changed as a result of using the AsIs' , CompositeCMYK' or Composite CMYK and Spot' colour output options (again assuming theColour manage sources to destinations' check boxes are all OFF in the SourceSetup)?
2. Do any of the AsIs', Composite CMYK' or Composite CMYK andSpot' colour output options use the Source Setup' settings to convert colourvalues in any way even when the Colour manage sources to destinations' checkboxes are switched OFF in the Source Setup?

Re: Preferences > Colour Manager
Considering all of the above:
a) Exactly what impact does the 'Enable Access to Picture Profiles' have on pictures imported into the layout, and at precisely what points in the workflow (e.g. importing a picture, exporting to PDF, etc.) does it have an impact?
b) If 'Enable Access to Picture Profiles' is checked ON, doesthis necessarily mean that QXP will go ahead and start altering the colour numbers in imported pictures at any stage between importing the picture and exporting the layout to PDF? Forgive me for the barrage of very basic questions, but I think some verysimple answers to these specific questions would help provide a much greaterunderstanding of what's going on under the hood with Quark's colour management,and what one needs to do to ensure what you get out on press is what you putin, with no surprises. We've had a few surprises outputting to PDF from QXP 8 so we're not about to go to version 9 until we know what's going on with what we already have.Please can you help?Many thanks,Head
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Postby Head » 14 Jun 2012, 01:41

Nobody?
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