Image size Ac to pdf?

[Mats Knutsson]

I'm playing with a mosaic project where I'll be painting an A2 with loads of images. I just did a quick test and to my surprise the file size of the exported pdf is reduced the more images I add to the layout. I wasn't expecting this!? I will print this mosaic on A2 canvas paper and need a decent resolution and am prepared for huge pdf file size but this attempt goes the other way. I think I don't know what's happening but maybe someone could shed a light?

/Br Mats 

[vistasp]

I could be wrong, Mats, but here's what I think. The PDF on the left has images that are tiled/repeated multiple times. The pixel colour data that needs to be stored, therefore, is much less than in the PDF on the right, where every image is unique.