Transparency and Color Management in InDesign CS4

[abccolor]

I am having difficulty maintaining correct color when combining RGB and CMYK artwork on an InDesign (CS4) artboard when transparency is applied.



Our workflow subscribes to a "late binding" methodology, where RGB and CMYK artwork are tagged with the correct ICC profiles upstream and final color conversions occur at the RIP. When RGB and CMYK artwork (without transparency) are included on the same InDesign artboard, the resulting PDF and print both present with expected color.



If artwork with transparency is introduced to the same artboard, the Transparency Blending Space is invoked, and we will experience a color shift in some of our imagery.



If the Document CMYK blending space is selected, our CMYK artwork with transparency maintains correct color, but our non-transparent RGB images appear to be converted to CMYK. We observe this conversion happening when the transparent object is placed on the artboard in InDesign, and it is consistent in the PDF and printed output.



If the Document RGB blending space is selected, our RGB images maintain correct color, but our CMYK artwork with transparency appears to be converted and loses detail.



Examples assume Adobe RGB, and CMYK SWOP color spaces only, and we do not wish to convert all imagery to one color mode before placement in InDesign.



Has anyone experienced this challenge, and have you developed a solution for maintaining correct color in all imagery?

 

[Pokei]

Have InDesign convert to your final CMYK space on export to PDF. You should be able to download the profile from your RIP and put it in your ColorSync folder on your computer.

This is the way I do all of my CMYK conversions with very good results.

 

[Lukas Engqvist]

What PDF settings are you using? PDF-x4 should be the best way to go.

Have used RGB for placed images for the past 10 years. If all CMYK is SWOP you have a very safe way to work, you will however need to decide what your RGB to CMYK rendering you want to use, perceptual or relative with blackpoint compensation.
Be carefull with tagging CMYK, you may want to look into letting CMYK follow safe CMYK practice, ie preserve CMYK values.

 

[leonardr]

I am having difficulty maintaining correct color when combining RGB and CMYK artwork on an InDesign (CS4) artboard when transparency is applied.

Has anyone experienced this challenge, and have you developed a solution for maintaining correct color in all imagery?

In addition to the other good comments, you should be sure to set the Isolation option on the objects that are in the non-blending space.

 

[abccolor]

Thank you to all for your input.

Pokei / Lukas - The conversion of the RGB is occurring upon placement of the transparent CMYK (not at output). If I have non-transparent CMYK on the artboard, no RGB conversion happens and the mixed mode artwork is successfully moved to the PDF. We wish for all RGB to CMYK conversions to happen at the RIP.

Leonardr - Where do I find the Isolation option?

Thanks

 

[abccolor]

Leonardr - I have located the Isolation option, but this appears to be for items in which the transparency effect has been applied within InDesign. My objects, which are being placed, already have transparency. I have attempted to apply the isolation to the CMYK, but the RGB objects on the page have already experienced the unwanted transformation. Thoughts?

 

[rich apollo]

Are your color management policies set to convert to working spaces? Are you flattening during export?

I much prefer to export without flattening or converting and handle color in the PDF files.

 

[abccolor]

Rich,

My color settings are set to "Preserve Embedded Profiles". My PDF Export settings are based on PDF/X-4:2008, with No Color Conversion and to Include All Profiles. We also honor Live Transparency to the PDF.

PLEASE NOTE: The color change is occurring upon object placement into InDesign. This is not something I am seeing only when printing or creating PDF’s. ALSO, if no transparent objects are being used on the artboard, the color profiles maintain correct color through the PDF process until final conversion at the RIP.

Thanks,

-Scott

 

[abccolor]

Looks like the pool is dry on this topic. Does everyone subscribe to early binding CMYK? Does anyone else work with transparency? Since this conversion does not produce a dialog box, has it just gone unnoticed? Even if nobody has an answer, have any of you experienced this problem?

 

[Lukas Engqvist]

I'm sorry I have exerienced very few colour management surprises that do not have an explanation. I am not saying that there are never colour shifts, just that there usually is an explanation.

I do not understand what you are asking for. If you are using transparency blend modes you will ofcourse need to invoke the transparency blend space because late binding still requires to know what you are binding. Keeping the highest level of abstraction possible is fine, but notice "as possible". If you do not invoke a blend space your abstraction will be so abstract it will be meaningless.

If you look at the maths behind the blend spaces you will find that the colour needs to be made into a number that needs to interact with the colour below. If you look at the screen blend mode as an example it will compare the numbers of the colour of the object with the colour of the pixel below, and then per channel pick the lightest colour value.

I.e RGB 100 100 100 over RGB 0 255 160 would give a colour 100 255 160
in this case you will have to have both RGB in the same colour space, how else can you compare wich is the lighter colour?
With CMYK 52 42 42 24 over 90 0 60 0, will give 52 0 42 0.
Note that an RGB colour interacting with a CMYK colour will yield different results depending on the UCR/GCR setting in the default CMYK profile in you colour settings if you have CMYK as the transparency blend space. (yes there is plenty more that could be written here I have tried to keep it as simple as I can)
Now attempting to do the equation between two different working spaces (especially when using one aditive colour model and one subtractive colour model) would be strange maths running into divide by zero problems etc.
Transparency limited to Alpha masks can be reliably abstracted, but any other blend mode will not work. (From photoshop it is the only kind of transparency supported.)

Corel Draw does not state the colour blend spaces, and believe me there what is worse that seeing a shift as you place an object is when everything is unpredictable. The reason that the change has to occur on placement is that it is the designer that has to make the decision... or would you rather the service bureau would make a guess? That the Rip, version, settings etc should make those decisions? That would be like throwing an abstract question at a bunch of philosophers and expect to get one answer.

To attept to understand why change happens does mean you will need a very stable understanding of colour, colour management, how colour is converted to numbers, and the maths of blending colours.

So to answer your question. There are some things in a document you can keep in device independant but there are other objects which will be different depending on output, and InDesign is just trying to help you to show you how the PDF print engine will interpret your design, changing your colour settings will let you try other colour management setup to see if that will give you a better result.

Note: Even when changing a photoshop document with adjustment layers or blend modes you will get the choice to flatten to preserve appearance. This ought to be enough to convince you that it is not possible to have both editability and appearance as output intent changes where transparency is used. Using object isolation mode is the equivalent of converting a group of layers to smart objects before doing the mode change. this means you have editability latent.