[scribus] PDFX3, CMYK and opacity

[JLuc]

Hello,

I have been struggling for the last days with generating the right PDF
for the big printer company that shall print it.

I have accepted the fogra27 color profiles in the document settings.
Fogra27 is also the color profile requested by the printer.

The printer requests PDF X3.
But when i set PDF output to be PDFX3, the "color" pane in "export to PDF" dialog
becomes grayed out and inactive.
As a consequence, I cannot choose anymore "printer" as a direction
("printer" means "CMYK").

As a result, printer says "some pictures are CMYK and some are RGB in your file".
That would probably lead to a color disaster.

X3 is a subset of PDF 1.3 and "color" pane is well disabled with PDF1.3.
So why is the "color" tab of "export to PDF" disabled
when "PDFX3" is choosen ?

And how to get a correct PDF ?
This is the most crucial question i have now.

Another problem / question i have is about opacity.
The first time i sent a PDF of that file it was PDF1.4
and there was a 70% opacity frame in it.
I choosed 1.4 since opacity or transparency is not available before 1.4,
but the printers cromalin (preprint trial) printed the 70% layer
with a 0% opacity that is : it wasnt printed at all !
So i decided to change the image so as to be able to include it with 100% opacity
but that would not have been possible if i had lots of pictures with opacity.
And what about backgrounds and texts ?

When i ask a PDFX3, that is a subset of PDF1.3, how do Scribus treat opacity ?
Does Scribus compute the equivalent colors points (rasterizing) at a 100% opacity ?
Or it includes the opacity instruction as it is, without caring that PDFX3
cannot handle this ?


Thanks in adavance for your lights...

JLuc