Okay, probably setting myself up for some abuse here but I thought I might have a crack at outlining how Quark CMS works (or at least how I think it works), as it seems to be one of the least understood parts of the Quark package.
I invite everyone to comment as it would be good to have a definitive post to refer new and returning users to.
Most people seem to be okay with Adobes CM implementation and have difficulty translating into Quark, this is most likely because Quark and Adobe have quite different approaches to colour management.
When you look at the Color Settings in Photoshop, you can see it is laid out so that you can choose color preferences for each image type (CMYK, RGB or Greyscale) which makes for a tidy and easily understood set up.
This apparent simplicity however, is largely due to the fact that Photoshop only ever deals with one kind of image at a time (an image will be either RGB, CMYK or Greyscale and either will, or will not, have a profile attached). Quark on the other hand, routinely deals with pages which can have multiple image types on it and therefore needs to manage a much more complex range of possibilities. It is probably worth mentioning at this point that PostScript (even level 3) cannot manage ICC data, for Photoshop this is not really a problem as it has other ways to attach ICC information to file formats - but for Quark to manage color output using ICC, it must apply the effects of ICC prior to output. The resulting PostScript output does not have ICC management contained alongside color data - the data has already been corrected and converted by Quark CMS.
Furthermore, Adobe mangages much of its color management internally (frequently using the ACE color engine) where Quark utilises calls to Apple Colorsync at the system level (where ACE is not available). For those of you who have tried to get colours to match on screen between Adobe and Quark applications - now you know why it never quite works!
Finally, it is worth noting that Quark CMS cannot color manage embedded images (filetypes eps, pdf, dcs etc) and no amount of set up in the Quark CMS dialog will affect how these images look on screen.
Quark CMS in more detail
-Color Management Active
Obviously this switches CMS on or off for the current document. Quite often this is the simplest and possibly safest way to operate provided you are aware that you will not be able to evaluate any color Quark shows you! The good news about this option is that you know for sure that Quark will not correct color at any point and your final output will reflect the input - right or wrong!
-Destination Profiles
This is where you set the color profiles for output.
The monitor profile is probably the most important setting here, it effectively tells Quark what colors your monitor is capable of displaying and will be used to map output colours to make them look right on your screen. The Monitor profile should be a profile used to linearise your monitor (these can be built using hardware and software calibrators or downloaded for manufacturers sites, Apples own monitor control panel can also build ICC profiles for your monitor). The listing here will show you all possible RGB output profiles based on your installed colorsync ICC list, this will include RGB profiles such as Adobe 1998 and sRGB - these are not suitable for this purpose, they are general RGB gamuts and are used elsewhere.
Composite and Separation output profiles should match your output devices. I guess Quark thought that users would proof as composite to a proofing device (composite profile) and then final output to a separation device (separation profile). This is obviously a little dated since most modern workflows are now composite PDF and Quarks separation technology is quite limited.
These output profiles can be set to match any profile in your Colorsync folder, or switched to none. When Quark CMS is active, you will notice that the profiles you set here are shown in a new profile tab in the Quark output window where they can be changed prior to output.
Its about here that users can get nervous that Quark CMS will take their carefully managed Photoshop images and mangle them to output something completely different - I won’t pull any punches, it is quite possible (and occasionally desirable) to get Quark CMS to do this - but only if you are careless with your CMS set up, so DON’T PANIC.
-Display Simulation
I’ll skip to this next as it is closely related to the Destination Profiles settings. Basically this option lets you define how you want Quark to show you softproofing on your monitor. It will take your chosen output condition (Monitor, Composite or Separation) and use your chosen monitor profile to map colors to your screen. This does beg the question - why would I choose my Monitor color space to render display correction? Well, if you switch off composite and separated profiles, Quark CMS will color correct based on your Default Source Profiles. If all you want to do is soft proof on screen this is quite a safe approach as it means that your PostScript output cannot be modifed when you print - see, I told you not to panic.
The downside to this approach is that Quark will not pick up and convert images which are saved in the wrong format (ie RGB images in a CMYK document) as you have switched off the output correction. However, it is arguable that using Quark to auto correct color spaces on output without operator knowledge is not necessarily a good thing!
-Default Source Profiles
These are the profiles Quark assumes are used when it encounters images which have no specified or attached profile. In essence, if an image is placed in Quark with no qualifying profile, then Quark must assume a profile in order to be able to manage the color at all - it needs a starting point.
The profiles used here are of the general colour space type (which we ignored in the monitor set up earlier). So RGB source profiles would be Adobe 1998, or ECI RGB - CMYK profiles would be SWOP coated or ISO uncoated etc. Because these are the assumed profiles for non profiled images, this is the assumed color space for your monitor display correction if you have not used composite or separated as a match.
Rendering intents will depend on your document content and type. In a print environment where your output cannot be RGB, I would suggest saturation for RGB solids and perceptual for RGB images. CMYK may be better working as colormetric since conversions are not so likely to fall outside of gamut.
- Color Manage sources to destinations
This is possibly the most risky switch in the Quark CMS set up. When this switch is off, Quark CMS will only apply actual color correction when an image is in the wrong color space format for the chosen output (ie, an RGB image will be converted when ouput into a CMYK print stream), this is the normal operation for Quark CMS and can save you from spoiling output if you miss an RGB image - remember this behaviour can always be switched off in the profile output tab or by setting destination profiles to none.
However, when this switch is on, Quark CMS will alter all output to a single profile (ie, all images, tagged, RGB, CMYK untagged may be converted to your output profile when printed) which is generally a far less desirable scenario - not to say this option doesn’t have its uses, but problems matching color after this type of conversion are going to be quite difficult to explain to a client!
phew!
I believe this information is correct, I’m sure someone out there will be happy to correct me if not, but hopefully a useful starting point!
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Tim Jones
Target Direct Print
