Print options - Imagesetting - overprinting ???

[StephanP]

Never leave text under any shadow effects nor any transparent image, otherwise your text is turned into a bitmap when exported as PDF x1a.

Good point and definitely worth remembering.
But we're talking about simple box shapes with some text floating above.

But if your printer finds that there are still knock outs I believe this is not the case.
I am sure there are no knock outs if you look at your file in XaraXtreme under overprinted black text.

Though I cannot check this myself, I don't believe that my printer is making these knock-outs up. So I am inclined to believe that Xara - despite object options "Overprint Fill" - exported the PDF/X with knock-outs.

I just moved the black texts to a new layer and will be sending off a new PDF to the printer's. Hopefully more news tomorrow.

Stephan

[alexbozhenov]

Hmm... Just made two identical files - one in Xara, second in AI (I made a few shapes filled with different colors and above that shapes I placed black text, and appointed to the black text to be overprinted), saved them as PDFs. Checked both in Acrobat -- Output Preview.

In the PDF file from AI black text shown as overprinted (select Color Warnings), and if you uncheck Process Black (select Separations), the rest shapes will be untouched (means there is an overprinting actually).

The same drawing saved as PDF from Xara, shows the black text as overprinted (in Color Warnings) but when uncheck Process Black in Separations I see the white holes -- no overprinting.

But! I have a plug-in for prepress for Acrobat (Enfocus PitStop), so with the help of this tool I have found that the difference between these two PDF files is in the methods of overprinting -- in PDF from AI overprinting method is "Illustrator Overprint Method (OPM 1)", in the PDF generated from Xara this method is "Standard Overprint Mode (OPM 0)"

Didn't make any deeper investigation yet (there are another ways to check overprinting), I hope will be able to do that a bit later...

[StephanP]

Very interesting indeed.
I've made Xara Support aware of your findings.
Stephan

[Luciano]

Stephan,

I hope you get any reply from Xara, as this problem was discussed in 2007 ( http://talkgraphics.com/showthread.php?t=25960 ), but I believe overprinting type still remains the same in XX pro 4 today.
I think that Xara PRO should generate a perfect professionally printable pdf file without the help of any other software.
This should be a simple improvement, but the real passport to enter the pro market and convince users that Adob$e is not the only software around.

Did you get your booklet printed in the end?

regards
Luciano

[alexbozhenov]

I think that Xara PRO should generate a perfect professionally printable pdf file without the help of any other software.
This should be a simple improvement, but the real passport to enter the pro market and convince users that Adob$e is not the only software around.

Completely agree with you -- until Xara make several small but serious improvements to their great prog, we still have to use Adobe or third-party progs...

I adore Xara, it's a very very useful and convenient tool to make drawings, but these small imperfections or defects really make me a bit sad, since such a great prog wouldn't have a significant segment and widely-known tool for designers around the world.

Situation looks a bit funny: we have great vector drawing tool, but sometimes can't get predictable or standard results when pro-printing... So we can draw, but can't print or distribute it following some standards. Anyway, I sticked to Xara since it was a CorelXara 1.2 )

[alexbozhenov]

Found some info from Adobe:

Illustrator overprint mode (OPM) is an addition to the standard overprinting (OP).

If OP is 1, the object on top overprint the object underneath. So far so good.
Unfortunately this does NOT work if both Objects are of type DeviceCMYK.

Example: You have a black text that is defined in 0/0/0/100 and is set to overprint, it still knocks out the CMY channel of the object from underneath. Only if the object underneath is of type Device-N (e.g. SpotColor), than the color underneath is not knocked out. You can very easy see that in the output preview.

If you want that the black text on top does not knock out the CMY color of the object underneath, you have to specify OPM=1.

Info: Only those color channels from the object underneath are not knocked out, the are defined as 0% in the object above. if your black was define 1/1/1/100, then overprinting would not make any difference, since the is no channel with 0%. Again - define such objects and check in the Acrobat Output Preview.

In other words: if you have 2 DeviceCMYK objects and you want the one on top to overprint the one underneath, you have to activate OPM. You could also name it CMYK-overprint. since this is a behaviour that you would expect OPM should always be 1.

[StephanP]

Well Alex,
I think you just found the source AND the solution to our little problem. Tops!
It'd appear to me as a trivial thing to take up in a next upcoming patch update from Xara.

Stephan

[Luciano]

Stephan,
using Alex information I edited a pdf file from Xara through a Hex editor (you can use a hex editor or any ASCII editor).
I replaced all the strings with:
/op true>
with:
/op true/ OPM 1 >

Now all overprint is correct as needed for printing.
See picture and before.pdf and after.pdf

[behzad]

again I like to point to the fact that your printer can not take care of trapping of colors on his side that is why he is requesting overprint of black text.

[alexbozhenov]

again I like to point to the fact that your printer can not take care of trapping of colors on his side that is why he is requesting overprint of black text.

I agree. I had just a few times when I was asked to do overprint for the Black text. But fortunately I have AI to correct output PDFs. Also special tools (plug-ins) for Acrobat is very helpful.

I followed recommendations from Adobe and made Black as 1, 1, 1, 100 and set to overprint. Shapes below the text were CMY -- there is still knockout.

Only when I defined all CMY shapes as spot colors, there was a correct overprinting. But I am not sure if this way is correct. So manual editing of PDF to set up overprint mode to OP 1 is the only way (if you don't have plugins for Acrobat etc) for Xara users.