Corel and blending space

[Lukas Engqvist]

Don't often get much from Corel, but now I have a case where we got a print ready PDF and things were not so sucessfull. All dark colours appear over saturated.
I try to anylise the file and it is a PDF 1.5 (though I have asked the customer for an x1a) It contains layers and the objects (product pictures) are transparent. The Product pictures also have a drop shadow, I don't know how this is acheived in Corel , but pitstop tells me the images are transparent with multiply and blending mode colour also transparency blend space is DeviceRGB
Can anyone guied me in the dark arts of Corel?

 

[leonardr]

If the objects on the page are in RGB, then having the blending space as RGB is a VERY GOOD THING! if the objects on the page are CMYK, then you can use Acrobat's tools to easily change the blending space to CMYK to match the objects (or flatten transparency all together if you so desire).

 

[Lukas Engqvist]

The objects on page were CMYK, but the Blending space RGB, this is what confuses me. Could you clarify why you think it is a "very good thing"? As far as all my experience goes it is asking for trouble, unless ALL data is RGB and the output intent is RGB. What happens is that the Adobe Pdf Print Engine multiplies the the channels in RGB space causing all dark areas to be filled with 100% K, the result being very different from any possible view of the PDF file.
I did try to flaten transparency in Acrobat, but stll do get artifacts. The problem is that the flatttening also simplifies the images loosing texture.
In InDesign there is a setting for transparency flattening and rendering intent for afterblending transparency. These settings are not available in APPE (at least not in ApogeeX 5).
I have managed to get a satisfactory outcome, but wanting to find out why this is happening, how to predict it and avoid such disasterous renderinig as what has happened.

Left Unflattened PDF through APPE. Right same PDF after pre-flattening in Acrobat before sending to APPE.

 

[leonardr]

The objects on page were CMYK, but the Blending space RGB, this is what confuses me. Could you clarify why you think it is a "very good thing"? As far as all my experience goes it is asking for trouble, unless ALL data is RGB and the output intent is RGB.

I think you read my message wrong. I agree with you 100%!

If all the objects are RGB, then the blending space should be RGB - and in PDF/X-4, the colorspace of the OutputIntent is used as the default blending space.

 

[Lukas Engqvist]

I would say if objects are RGB AND output Device is RGB then RGB is blendspace.
I read it several times and tried to understand what you mean by "you can use Acrobat's tools to easily change the blending space to CMYK to match the objects".
I did not find such a tool.
The file from Corel all objects are Device CMYK. Using Pitstop to inspect an object it says DeviceCMYK.
If I convert to a PDFx using export in Acrobat9, the drop shadows. (device CMYK, blend mode multiply) dissapear. Also the tone of the background changes (this was originally a device CMYK object 10 C and 2M after conversion to X4 it reads 14.4, 0.3, 4.0, 0.0 as I understand exporting to PDF X should not convert device CMYK)
Using the flattener has dissadvantage of resampling giving edge artifacts while resampling and bluring the images. There is no way to flatten at the resolution of top image?

The customer did try to export as a PDFx1a from Corel, but the colours were a disaster…Â*I can't see how results can be so different. (Quite frustrated by "print (not so) ready PDF" as you may be able to read between lines.

 

[Lukas Engqvist]

OK found in transparency flattener that there is a place to set "page level transparency Blending Color space" Here I can also coose ICC profile so that I get correct TAC, wich I was missing in the other places. That is the dialog I was missing in my frustration.
If a profile is selected then the resuling image tiles are tagged with that profile, and so must be decalibrated if it is not the same as the output intent (compare that in the export only allows a limited number of profiles in the PDFx export)

 

[Glenn McDowall]

sorry to resurrect such an old thread but how can I change the transparency blending color space in a pdf without flattening?

 

[Stephen Marsh]

There is a preflight fixup in Acrobat Pro that can change the blending space, screenshot attached (I have not verified that it does not flatten, so use with caution on copies until you know for sure).

Hope this helps,

Stephen Marsh

 

[Glenn McDowall]

Thanks Stephen, I'm not very familiar with Preflight Fixups so may be doing something wrong, I've created a custom one the same as your screen-shot (Fog39) but setting When: to Always (Override Existing), then I hit the Fix icon (spanner/wrench) at the bottom right and it brings up a Save As dialogue. But my resulting File still has sRGB as its Page-Level transparency Blending Space.
Am I doing something wrong or is this fixup working at an object level rather than a page level?

I've had a couple of files either go wrong in the RIP recently, one just errors when trying to generate a thumbnail or plate, one displays white in Acrobat but renders an originally rgb object I've converted to cmyk as a dark brown. Both were transparent files, both rgb (I'm guessing never designed for print purposes). I've always worked to the advice of sorting out the Colour spaces before flattening but I'm now wondering if RGB pdfs with RGB blending space should be worked the other way round, so flatten first then convert to CMYK? do you have any thoughts?

 

[David Milisock]

CorelDRAW what version? Anything older then X5 was application color managed and could not embedd profiles in a PDF. X3 and X4 had default CMYK working color spaces however could be set to work in RGB color mode and rtender transparency in either mode. In either case all versions of CorelDRAW allow Spot color, RGB and CMYK elements to reside in the same document.

Version 12 and older only rendered transparency as RGB, X3 and newer can render transpareny as RGB, N color and CMYK.

CorelDRAW X5 has a native color mode for PS, EPS and PDF and Embedds all profiles including grayscale. Also CorelDRAW allows the user to select the rendering resolution of effects.

 

[Lukas Engqvist]

I'm sorry three years is a long time to remember a job I don't remember what version of Corel it was, just that I couldn't get it to work any way I tried.

 

[David Milisock]

What 3 years and you forgot a job!!! At that age it was X4 at the newest and most likely older. Like all graphic files CorelDRAW files suffer from lack of user attention/knowlwdge. A PDF file does not make itself and if the native file was created by a 1 D 10 T you're screwed. It used to be that the designer made a lousy file and th eprinter fixed it, now we get files that the printer smake and they are like to old designers files. Seeing this alot as I have moved more into project management,

 

[Glenn McDowall]

Sorry David, perhaps I should have started a separate thread. I only have PDF's, one lists Publisher and the other list InDesign as creator. I'm converting rgb to cmyk using Acrobat's Color Converter and suspect that leaving the Page Level Transparency Blending Space as rgb is causing my RIP problems.

 

[David Milisock]

Are there embedded ICC profiles in your PDf file?

 

[Glenn McDowall]

Yes, on one file they are all sRGB when I start, Images and vector. As I mentioned I don't think the creator ever intended this file to be printed.

 

[David Milisock]

If it were me I would open in Acrobat with PitStop Pro, convert all fonts to outlines, save the file and open in CorelDRAW X5 and do the color conversion there via one of several available processes it could be done via the Corel PubLish to PDF using soft proof applying the conversion there. That is if only color is the issue. Acrobt color conversions usually leave something to be desired.