[scribus] Reducing photo filesizes and dpi for PDFs

[Rolf-Werner Eilert]

This thread was "Concatenating PDFs - quality?" and I tried to answer to 
it, but it seems nobody is following that thread anymore, so I open a 
new one with a more obvious title.

As a reminder: This is on 1.3.3.x

I have tried several settings. It's correct, resetting the dpi the way 
John said just results in "enlarging" the optical appearance of the 
image within the frame. This seems logical to me.

Setting the PDF export dialog to 300 dpi should do the job, but I'm not 
sure it really does. I splitted up my book into 4 files to keep loading 
times low. Compared to the other ones, one of the parts produces 
untypically large PDFs (over 100 MB instead of 30 - 50).

So I tried to leave out certain pages to test which images might produce 
this. First I left out a double page showing one large map, but it 
reduced file size merely from 138 to 126 MB. Then I tried to leave out 
the first double page which contains many small photos. Now I got 103 MB.

That's strange because IF all photos are automagically reduced to the 
300 dpi set in the export dialog, they will make much less image surface 
(and thus dots) than that single large map. There is also some text on 
the page and gaps between the photos.

Watching the resulting PDF in Adobe Reader, I can enlarge up to 400 % 
and still don't see any pixeling. Instead, the "grain" of the pictures 
comes up. I guess that's way too high for the printing machine...

Do I have a chance to verify the resolution of the pictures in the PDF?

Rolf