Exporting complex Xara transparencies that Illustrator can see

If you try to export certain graphics with three or four point transparencies, Illustrator won't understand them when opening a .pdf file. It will not apply any transparency at all.
I have attached a .pdf which Illustrator will reproduce a four point repeating transparency quite faithfully.
I was trying to make a realistic brown paper bag texture to clip inside a shape and ran into this problem.
The solution? Group the object(s) to which the transparency has been applied. This allows you to now apply a further transparency. In this particular case, I applied a flat transparency and exported a high quality .pdf which Illustrator was pretty ecstatic about.
I expect most of you are familiar with the technique of grouping tansparent objects to apply further transparencies, but you may not of thought of this handy method for exporting to other vector applications.
Bob.

HI Bob,

I often have more success with svg for these exports to AI, but it doesn't support line profiles (bug)
Also when converting to cmyk the transparency masks often change intensity with a svg source.

PDF often leaves me with bitmaps on group transparencies.
What PDF setting/version have you used?

There should be a compatibility chart!

Marc

Hi Marc, on closer examination and releasing plenty of clipping masks, I do in fact end up with a bitmap. The setting I used for export was 300 dpi commercial printing.
I think I was flushed with success upon getting Illustrator to present what looked like a transparency in the finished result. Oh well, back to the drawing board. I'll have a look at svg.
Bob.

It's the PDF filter as well that's causing the problem. If you did the same in Illy, which you cant, exported it as a PDF the programme would highlight the transparency and state that there was a problem. Then it would ask you to go back and flatten the area which Xara does automatically.