Source Profile's relationship to Output Profile

Discuss QuarkXPress color management functionality including DeviceN workflows

Source Profile's relationship to Output Profile

Postby Head » 14 Jun 2012, 01:41

Nobody?
Head
 
Posts: 6
Joined: 17 Aug 2010, 03:38

Source Profile's relationship to Output Profile

Postby Graham PM (Quark) » 18 Jun 2012, 17:31

Let me preface this by saying I am not 100% up to speed on how color works in QXP8, which left R&Ds hands a long time ago, but of course I know the way it works today, and so I should think what I am about to spout is close.I understand this is a Dark Arts, subject, but I am struggling to come up with a more straightforward answer.The answer I give here is somewhat simplified because there are some edge twists and turns that just make things more complicated than they need be, so I am going to skip those codicils unless someone insists otherwise.First, some explanationsthe data for a bitmap image, always has a "colourspace".There are lots and lots of colourspaces, but only two that need concern us here, DeviceCMYK, and ICCProfileBased(CMYK).Then, there are devices. monitors, printers, scanners, cameras, etc. We are interested here in the input device (let's say it is a camera), and the output device (printer).DeviceCMYK says that the image data is already in the colourspace of the output device.ICCProfileBased says the image data is in the colourspace of a different device, most likely the input device, and must be converted to the output device space.QXP writes the final PostScript data in DeviceCMYK space: so the contract is, that all the data PostScript sees, is already converted to output space.The description of that output device you can control in the output setup dialogs. Let's say, you want your target device to be a sheet fed Heidelberg device printing on X gram substrate (paper). You have the ICCProfile for that set up. You set that in the output set up as the device all your work is going to.So now the idea is that all pictures, text, lines, paths etc, should either be supplied directly in colour descriptions in that output set up, OR a mechanism is given to PostScript to do the conversion. If there is a mismatch of colourspaces, there will always be a conversion at some point in the pipeline: either QXP will take care of it, or PostScript will do it.If your images have no profile, then the contract says, that they output in DeviceCMYK. i.e. for good or bad no conversion takes place in output.However, if your images have an embedded profile, or you have assigned a profile to them via the input set up, then the contract says, a conversion must take place to get the data into the output device space, (unless the images have exactly the same profile as the output space). If you have told Photoshop to embed the Sheetfed Heidelberg profile, then, I would expect your image would be sent straight to PostScript as DeviceCMYK, because the input and the output colourspaces match. Only if the images advertise themselves in a different colourspace, must some conversion take place.For screen, a conversion MUST ALWAYS take place, because the screen is RGB. QXP will always use the profile that describes your screen monitor to do that conversion. Problems occur either when users have assigned the wrong profiles to the source images, or the wrong profile to the monitor. Easy enough to do.Finally, back to who does the conversions, if they must take place.Normally QXP does the conversion, because it wants to write out DeviceCMYK.However, you can ask QXP to hand off this job to PostScript. What happens there is that the entire ICCProfile is embedded in the PostScript output, This is called a CIE, and you make that happen by creating an Output Setup that is AsIs with the color management box checked.Personally, I don't see the point in this, for technical reasons that I won't bore you with. Nevertheless, the option is there.I can expand on all this further if you want.
Graham PM (Quark)
 
Posts: 392
Joined: 15 Mar 2005, 09:57

Source Profile's relationship to Output Profile

Postby Graham PM (Quark) » 18 Jun 2012, 17:36

I meant CSA not CIE. Acronyms tend to blur into a spludge after a while.
Graham PM (Quark)
 
Posts: 392
Joined: 15 Mar 2005, 09:57

Source Profile's relationship to Output Profile

Postby Head » 19 Jun 2012, 03:24

Hi Graham,
Many thanks for this, and for keeping it simple. It's a tad too simple though to help with the specifics that I was enquiring about, and leaves me stuck with two really crucial questions:


[b]1. Source Setup preference
Is it possible that you could clarify what role the Source Setup preference has within the workflow described?

Does it simply tell QXP what input colour space it should assume for any imported pictures that don't have their own profiles embedded? Or is it more than this?
And what does one need to consider in order to make an informed decision on how to set this up from the choices provided (i.e. 'QuarkXPress Emulate Legacy', 'QuarkXPress 7.0 default') or whether to use a custom setting?

[b]2. Colour manage sources to destinations
You said above that "If there is a mismatch of colour spaces there will always be a conversion at some point in the pipeline."

Will such a conversion take place even when the 'Colour manage sources to destinations' option is OFF (unchecked) within the chosen source setup preference?
If the answer to this is 'Yes', what then does the 'Colour manage sources to destinations' option actually do?


Please could you clarify these two points as queried, as I believe this will be of great value to users and may begin to shed some light on some of the other questions raised in this thread.

Many thanks once again, in anticipation of your valued input which is greatly appreciated.
Head
 
Posts: 6
Joined: 17 Aug 2010, 03:38

Source Profile's relationship to Output Profile

Postby Graham PM (Quark) » 19 Jun 2012, 08:55

Perhaps a rudimentary analogy to the Queen's English might work here. Let's start with the assertion that if everyone spoke like the Queen, there would be no disagreement about what was meant. But of course, only the Queen speaks like that. So we have a system, whereby, dialects of English can be converted to and from Queen's English. For these conversions, you need a language profile. In order for Blane from California to completely understand Jimmy from Glasgow, we need to assign Jimmy a Glasgow-To-Queens English profile, and Blane a Queens-English-To-Californian profile. Thus (Are Ye Hallrite Jimmy) maps to (How Are You, Sir) maps to (S'up Dude). If Jimmy forgot to bring his profile along to the meeting, then (Are Ye Hallrite Jimmy) passes through to Blane directly, who pretends to understand Jimmy but is now confused about whether or not to call the paramedics. So the moral here is that although everyone is speaking English, the results can be unpredictable if someone doesn't bring his profile. In the old days, there were no profiles, and there are still lots of people like Jimmy in the world, fine citizens of the world, but with no profile in their back pockets. Nowadays the profiles are so good you can even find out how many Stovies he had before the meeting. All very well for us, but what about those older Jimmys? That is where you need the extra control of the source set up. Let's say Jimmy walks into a meeting in the UC Berkeley Campus without his profile book. To get the gist of what he is saying, we can give him a profile. If he is wearing jeans and a T, we haven't got anything to go on, so we might give him a Generic UK profile. This will at least translate Lift to Elevator, and so on, but probably won't translate pints of Heevy. If his T shirt has Scotland on it, we can try Generic Scottish, or even better if it has Celtic or Rangers, we can pinpoint him to the East or West side of Glasgow. This is what source set up supports. In addition, we may only want to use that translation when showing previews on screen. We might have some reason why we want (Are Ye Hallrite Jimmy) to print directly to PostScript. In which case, in the source set up dialog, make sure mapping English to English is not checked.
Graham PM (Quark)
 
Posts: 392
Joined: 15 Mar 2005, 09:57

Previous

Return to QuarkXPress 8, 9 & 10: Color management

Who is online

Users browsing this forum: No registered users and 1 guest