[scribus] Concatenating PDFs - quality?

[Rolf-Werner Eilert]

Am 24.12.2011 07:46, schrieb Peter Nermander:
>> After that to adjust the DPI right click on the graphics frame, select
>> "Properties" and then  on the pop up menu select "Image".
>> Remember you can adjust dpi down but adjusting up is not likely
>> to yield good results.
>
>>   (Haven't tried that yet, though
>
> You should hav tried, because it will not work.
>
> The DPI shown in the Properties palette is based on the number och
> pixels and the physical size of the imaga. Changing it will rescale
> the image, not resample it.
>
> The correct way is, as Rob wrote, to set the desired DPI in the PDF
> export dialog.
>
>
> But I think it would also be good if rescaling and a few similar
> action could be included as Image Effects.
>
>
> /Peter
>

Hi Peter,

Hope you see that I answer to this thread only now.

I just 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.

Setting the 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 the one 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 check for the resolution of the pictures in the PDF?

Rolf