[Scribus] Light halftone background in tiff image

[Leonard Sitongia]

Hi,

I've just started using Scribus.  Thank you for this great software!  My 
apologies for my lack of knowledge of the proper terminology in the 
following.

I'm using The Gimp to create a masthead for a newsletter.  I've composed 
it with a transparent background.  I've saved it as a TIFF image.  When 
I check with color picker, the values of the background are all 255 (white).

I've added it to a page in Scribus.  When I print the page out (exported 
to PDF), the masthead, this TIFF image, comes out with a very faint grey 
background, which looks like halftone, with a uniform pattern of black 
dots in the background, creating the faint grey.

I've tried a number of different configurations for color for the PDF 
export.

The grey doesn't appear to be in the image.  Is it created by the 
printer or by Scribus?

Thanks for your help!
==Leonard